7 files changed, 844 insertions, 0 deletions

diff --git a/arch/mips/include/asm/cdmm.h b/arch/mips/include/asm/cdmm.h
new file mode 100644
index 000000000000..b7d520f28d30
--- /dev/null
+++ b/arch/mips/include/asm/cdmm.h
@@ -0,0 +1,87 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2014 Imagination Technologies Ltd.
+ */
+#ifndef __ASM_CDMM_H
+#define __ASM_CDMM_H
+
+#include <linux/device.h>
+#include <linux/mod_devicetable.h>
+
+/**
+ * struct mips_cdmm_device - Represents a single device on a CDMM bus.
+ * @dev:        Driver model device object.
+ * @cpu:        CPU which can access this device.
+ * @res:        MMIO resource.
+ * @type:       Device type identifier.
+ * @rev:        Device revision number.
+ */
+struct mips_cdmm_device {
+        struct device           dev;
+        unsigned int            cpu;
+        struct resource         res;
+        unsigned int            type;
+        unsigned int            rev;
+};
+
+/**
+ * struct mips_cdmm_driver - Represents a driver for a CDMM device.
+ * @drv:        Driver model driver object.
+ * @probe       Callback for probing newly discovered devices.
+ * @remove:     Callback to remove the device.
+ * @shutdown:   Callback on system shutdown.
+ * @cpu_down:   Callback when the parent CPU is going down.
+ *              Any CPU pinned threads/timers should be disabled.
+ * @cpu_up:     Callback when the parent CPU is coming back up again.
+ *              CPU pinned threads/timers can be restarted.
+ * @id_table:   Table for CDMM IDs to match against.
+ */
+struct mips_cdmm_driver {
+        struct device_driver    drv;
+        int                     (*probe)(struct mips_cdmm_device *);
+        int                     (*remove)(struct mips_cdmm_device *);
+        void                    (*shutdown)(struct mips_cdmm_device *);
+        int                     (*cpu_down)(struct mips_cdmm_device *);
+        int                     (*cpu_up)(struct mips_cdmm_device *);
+        const struct mips_cdmm_device_id *id_table;
+};
+
+/**
+ * mips_cdmm_phys_base() - Choose a physical base address for CDMM region.
+ *
+ * Picking a suitable physical address at which to map the CDMM region is
+ * platform specific, so this weak function can be defined by platform code to
+ * pick a suitable value if none is configured by the bootloader.
+ *
+ * This address must be 32kB aligned, and the region occupies a maximum of 32kB
+ * of physical address space which must not be used for anything else.
+ *
+ * Returns:     Physical base address for CDMM region, or 0 on failure.
+ */
+phys_addr_t __weak mips_cdmm_phys_base(void);
+
+extern struct bus_type mips_cdmm_bustype;
+void __iomem *mips_cdmm_early_probe(unsigned int dev_type);
+
+#define to_mips_cdmm_device(d)  container_of(d, struct mips_cdmm_device, dev)
+
+#define mips_cdmm_get_drvdata(d)        dev_get_drvdata(&d->dev)
+#define mips_cdmm_set_drvdata(d, p)     dev_set_drvdata(&d->dev, p)
+
+int mips_cdmm_driver_register(struct mips_cdmm_driver *);
+void mips_cdmm_driver_unregister(struct mips_cdmm_driver *);
+
+/*
+ * module_mips_cdmm_driver() - Helper macro for drivers that don't do
+ * anything special in module init/exit.  This eliminates a lot of
+ * boilerplate.  Each module may only use this macro once, and
+ * calling it replaces module_init() and module_exit()
+ */
+#define module_mips_cdmm_driver(__mips_cdmm_driver) \
+        module_driver(__mips_cdmm_driver, mips_cdmm_driver_register, \
+                        mips_cdmm_driver_unregister)
+
+#endif /* __ASM_CDMM_H */
diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
index b99729e36860..cbddbaddb347 100644
--- a/drivers/bus/Kconfig
+++ b/drivers/bus/Kconfig
@@ -20,6 +20,19 @@ config IMX_WEIM
           The WEIM(Wireless External Interface Module) works like a bus.
           You can attach many different devices on it, such as NOR, onenand.
 
+config MIPS_CDMM
+        bool "MIPS Common Device Memory Map (CDMM) Driver"
+        depends on CPU_MIPSR2
+        help
+          Driver needed for the MIPS Common Device Memory Map bus in MIPS
+          cores. This bus is for per-CPU tightly coupled devices such as the
+          Fast Debug Channel (FDC).
+
+          For this to work, either your bootloader needs to enable the CDMM
+          region at an unused physical address on the boot CPU, or else your
+          platform code needs to implement mips_cdmm_phys_base() (see
+          asm/cdmm.h).
+
 config MVEBU_MBUS
         bool
         depends on PLAT_ORION
diff --git a/drivers/bus/Makefile b/drivers/bus/Makefile
index 2973c18cbcc2..807dd17ef2f8 100644
--- a/drivers/bus/Makefile
+++ b/drivers/bus/Makefile
@@ -4,6 +4,7 @@
 
 obj-$(CONFIG_BRCMSTB_GISB_ARB)  += brcmstb_gisb.o
 obj-$(CONFIG_IMX_WEIM)  += imx-weim.o
+obj-$(CONFIG_MIPS_CDMM) += mips_cdmm.o
 obj-$(CONFIG_MVEBU_MBUS) += mvebu-mbus.o
 obj-$(CONFIG_OMAP_OCP2SCP)      += omap-ocp2scp.o
 
diff --git a/drivers/bus/mips_cdmm.c b/drivers/bus/mips_cdmm.c
new file mode 100644
index 000000000000..5bd792c68f9b
--- /dev/null
+++ b/drivers/bus/mips_cdmm.c
@@ -0,0 +1,716 @@
+/*
+ * Bus driver for MIPS Common Device Memory Map (CDMM).
+ *
+ * Copyright (C) 2014-2015 Imagination Technologies Ltd.
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/atomic.h>
+#include <linux/err.h>
+#include <linux/cpu.h>
+#include <linux/cpumask.h>
+#include <linux/io.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/smp.h>
+#include <asm/cdmm.h>
+#include <asm/hazards.h>
+#include <asm/mipsregs.h>
+
+/* Access control and status register fields */
+#define CDMM_ACSR_DEVTYPE_SHIFT 24
+#define CDMM_ACSR_DEVTYPE       (255ul << CDMM_ACSR_DEVTYPE_SHIFT)
+#define CDMM_ACSR_DEVSIZE_SHIFT 16
+#define CDMM_ACSR_DEVSIZE       (31ul << CDMM_ACSR_DEVSIZE_SHIFT)
+#define CDMM_ACSR_DEVREV_SHIFT  12
+#define CDMM_ACSR_DEVREV        (15ul << CDMM_ACSR_DEVREV_SHIFT)
+#define CDMM_ACSR_UW            (1ul << 3)
+#define CDMM_ACSR_UR            (1ul << 2)
+#define CDMM_ACSR_SW            (1ul << 1)
+#define CDMM_ACSR_SR            (1ul << 0)
+
+/* Each block of device registers is 64 bytes */
+#define CDMM_DRB_SIZE           64
+
+#define to_mips_cdmm_driver(d)  container_of(d, struct mips_cdmm_driver, drv)
+
+/* Default physical base address */
+static phys_addr_t mips_cdmm_default_base;
+
+/* Bus operations */
+
+static const struct mips_cdmm_device_id *
+mips_cdmm_lookup(const struct mips_cdmm_device_id *table,
+                 struct mips_cdmm_device *dev)
+{
+        int ret = 0;
+
+        for (; table->type; ++table) {
+                ret = (dev->type == table->type);
+                if (ret)
+                        break;
+        }
+
+        return ret ? table : NULL;
+}
+
+static int mips_cdmm_match(struct device *dev, struct device_driver *drv)
+{
+        struct mips_cdmm_device *cdev = to_mips_cdmm_device(dev);
+        struct mips_cdmm_driver *cdrv = to_mips_cdmm_driver(drv);
+
+        return mips_cdmm_lookup(cdrv->id_table, cdev) != NULL;
+}
+
+static int mips_cdmm_uevent(struct device *dev, struct kobj_uevent_env *env)
+{
+        struct mips_cdmm_device *cdev = to_mips_cdmm_device(dev);
+        int retval = 0;
+
+        retval = add_uevent_var(env, "CDMM_CPU=%u", cdev->cpu);
+        if (retval)
+                return retval;
+
+        retval = add_uevent_var(env, "CDMM_TYPE=0x%02x", cdev->type);
+        if (retval)
+                return retval;
+
+        retval = add_uevent_var(env, "CDMM_REV=%u", cdev->rev);
+        if (retval)
+                return retval;
+
+        retval = add_uevent_var(env, "MODALIAS=mipscdmm:t%02X", cdev->type);
+        return retval;
+}
+
+/* Device attributes */
+
+#define CDMM_ATTR(name, fmt, arg...)                                    \
+static ssize_t name##_show(struct device *_dev,                         \
+                           struct device_attribute *attr, char *buf)    \
+{                                                                       \
+        struct mips_cdmm_device *dev = to_mips_cdmm_device(_dev);       \
+        return sprintf(buf, fmt, arg);                                  \
+}                                                                       \
+static DEVICE_ATTR_RO(name);
+
+CDMM_ATTR(cpu, "%u\n", dev->cpu);
+CDMM_ATTR(type, "0x%02x\n", dev->type);
+CDMM_ATTR(revision, "%u\n", dev->rev);
+CDMM_ATTR(modalias, "mipscdmm:t%02X\n", dev->type);
+CDMM_ATTR(resource, "\t%016llx\t%016llx\t%016lx\n",
+          (unsigned long long)dev->res.start,
+          (unsigned long long)dev->res.end,
+          dev->res.flags);
+
+static struct attribute *mips_cdmm_dev_attrs[] = {
+        &dev_attr_cpu.attr,
+        &dev_attr_type.attr,
+        &dev_attr_revision.attr,
+        &dev_attr_modalias.attr,
+        &dev_attr_resource.attr,
+        NULL,
+};
+ATTRIBUTE_GROUPS(mips_cdmm_dev);
+
+struct bus_type mips_cdmm_bustype = {
+        .name           = "cdmm",
+        .dev_groups     = mips_cdmm_dev_groups,
+        .match          = mips_cdmm_match,
+        .uevent         = mips_cdmm_uevent,
+};
+EXPORT_SYMBOL_GPL(mips_cdmm_bustype);
+
+/*
+ * Standard driver callback helpers.
+ *
+ * All the CDMM driver callbacks need to be executed on the appropriate CPU from
+ * workqueues. For the standard driver callbacks we need a work function
+ * (mips_cdmm_{void,int}_work()) to do the actual call from the right CPU, and a
+ * wrapper function (generated with BUILD_PERCPU_HELPER) to arrange for the work
+ * function to be called on that CPU.
+ */
+
+/**
+ * struct mips_cdmm_work_dev - Data for per-device call work.
+ * @fn:         CDMM driver callback function to call for the device.
+ * @dev:        CDMM device to pass to @fn.
+ */
+struct mips_cdmm_work_dev {
+        void                    *fn;
+        struct mips_cdmm_device *dev;
+};
+
+/**
+ * mips_cdmm_void_work() - Call a void returning CDMM driver callback.
+ * @data:       struct mips_cdmm_work_dev pointer.
+ *
+ * A work_on_cpu() callback function to call an arbitrary CDMM driver callback
+ * function which doesn't return a value.
+ */
+static long mips_cdmm_void_work(void *data)
+{
+        struct mips_cdmm_work_dev *work = data;
+        void (*fn)(struct mips_cdmm_device *) = work->fn;
+
+        fn(work->dev);
+        return 0;
+}
+
+/**
+ * mips_cdmm_int_work() - Call an int returning CDMM driver callback.
+ * @data:       struct mips_cdmm_work_dev pointer.
+ *
+ * A work_on_cpu() callback function to call an arbitrary CDMM driver callback
+ * function which returns an int.
+ */
+static long mips_cdmm_int_work(void *data)
+{
+        struct mips_cdmm_work_dev *work = data;
+        int (*fn)(struct mips_cdmm_device *) = work->fn;
+
+        return fn(work->dev);
+}
+
+#define _BUILD_RET_void
+#define _BUILD_RET_int  return
+
+/**
+ * BUILD_PERCPU_HELPER() - Helper to call a CDMM driver callback on right CPU.
+ * @_ret:       Return type (void or int).
+ * @_name:      Name of CDMM driver callback function.
+ *
+ * Generates a specific device callback function to call a CDMM driver callback
+ * function on the appropriate CPU for the device, and if applicable return the
+ * result.
+ */
+#define BUILD_PERCPU_HELPER(_ret, _name)                                \
+static _ret mips_cdmm_##_name(struct device *dev)                       \
+{                                                                       \
+        struct mips_cdmm_device *cdev = to_mips_cdmm_device(dev);       \
+        struct mips_cdmm_driver *cdrv = to_mips_cdmm_driver(dev->driver); \
+        struct mips_cdmm_work_dev work = {                              \
+                .fn     = cdrv->_name,                                  \
+                .dev    = cdev,                                         \
+        };                                                              \
+                                                                        \
+        _BUILD_RET_##_ret work_on_cpu(cdev->cpu,                        \
+                                      mips_cdmm_##_ret##_work, &work);  \
+}
+
+/* Driver callback functions */
+BUILD_PERCPU_HELPER(int, probe)     /* int mips_cdmm_probe(struct device) */
+BUILD_PERCPU_HELPER(int, remove)    /* int mips_cdmm_remove(struct device) */
+BUILD_PERCPU_HELPER(void, shutdown) /* void mips_cdmm_shutdown(struct device) */
+
+
+/* Driver registration */
+
+/**
+ * mips_cdmm_driver_register() - Register a CDMM driver.
+ * @drv:        CDMM driver information.
+ *
+ * Register a CDMM driver with the CDMM subsystem. The driver will be informed
+ * of matching devices which are discovered.
+ *
+ * Returns:     0 on success.
+ */
+int mips_cdmm_driver_register(struct mips_cdmm_driver *drv)
+{
+        drv->drv.bus = &mips_cdmm_bustype;
+
+        if (drv->probe)
+                drv->drv.probe = mips_cdmm_probe;
+        if (drv->remove)
+                drv->drv.remove = mips_cdmm_remove;
+        if (drv->shutdown)
+                drv->drv.shutdown = mips_cdmm_shutdown;
+
+        return driver_register(&drv->drv);
+}
+EXPORT_SYMBOL_GPL(mips_cdmm_driver_register);
+
+/**
+ * mips_cdmm_driver_unregister() - Unregister a CDMM driver.
+ * @drv:        CDMM driver information.
+ *
+ * Unregister a CDMM driver from the CDMM subsystem.
+ */
+void mips_cdmm_driver_unregister(struct mips_cdmm_driver *drv)
+{
+        driver_unregister(&drv->drv);
+}
+EXPORT_SYMBOL_GPL(mips_cdmm_driver_unregister);
+
+
+/* CDMM initialisation and bus discovery */
+
+/**
+ * struct mips_cdmm_bus - Info about CDMM bus.
+ * @phys:               Physical address at which it is mapped.
+ * @regs:               Virtual address where registers can be accessed.
+ * @drbs:               Total number of DRBs.
+ * @drbs_reserved:      Number of DRBs reserved.
+ * @discovered:         Whether the devices on the bus have been discovered yet.
+ * @offline:            Whether the CDMM bus is going offline (or very early
+ *                      coming back online), in which case it should be
+ *                      reconfigured each time.
+ */
+struct mips_cdmm_bus {
+        phys_addr_t      phys;
+        void __iomem    *regs;
+        unsigned int     drbs;
+        unsigned int     drbs_reserved;
+        bool             discovered;
+        bool             offline;
+};
+
+static struct mips_cdmm_bus mips_cdmm_boot_bus;
+static DEFINE_PER_CPU(struct mips_cdmm_bus *, mips_cdmm_buses);
+static atomic_t mips_cdmm_next_id = ATOMIC_INIT(-1);
+
+/**
+ * mips_cdmm_get_bus() - Get the per-CPU CDMM bus information.
+ *
+ * Get information about the per-CPU CDMM bus, if the bus is present.
+ *
+ * The caller must prevent migration to another CPU, either by disabling
+ * pre-emption or by running from a pinned kernel thread.
+ *
+ * Returns:     Pointer to CDMM bus information for the current CPU.
+ *              May return ERR_PTR(-errno) in case of error, so check with
+ *              IS_ERR().
+ */
+static struct mips_cdmm_bus *mips_cdmm_get_bus(void)
+{
+        struct mips_cdmm_bus *bus, **bus_p;
+        unsigned long flags;
+        unsigned int cpu;
+
+        if (!cpu_has_cdmm)
+                return ERR_PTR(-ENODEV);
+
+        cpu = smp_processor_id();
+        /* Avoid early use of per-cpu primitives before initialised */
+        if (cpu == 0)
+                return &mips_cdmm_boot_bus;
+
+        /* Get bus pointer */
+        bus_p = per_cpu_ptr(&mips_cdmm_buses, cpu);
+        local_irq_save(flags);
+        bus = *bus_p;
+        /* Attempt allocation if NULL */
+        if (unlikely(!bus)) {
+                bus = kzalloc(sizeof(*bus), GFP_ATOMIC);
+                if (unlikely(!bus))
+                        bus = ERR_PTR(-ENOMEM);
+                else
+                        *bus_p = bus;
+        }
+        local_irq_restore(flags);
+        return bus;
+}
+
+/**
+ * mips_cdmm_cur_base() - Find current physical base address of CDMM region.
+ *
+ * Returns:     Physical base address of CDMM region according to cdmmbase CP0
+ *              register, or 0 if the CDMM region is disabled.
+ */
+static phys_addr_t mips_cdmm_cur_base(void)
+{
+        unsigned long cdmmbase = read_c0_cdmmbase();
+
+        if (!(cdmmbase & MIPS_CDMMBASE_EN))
+                return 0;
+
+        return (cdmmbase >> MIPS_CDMMBASE_ADDR_SHIFT)
+                << MIPS_CDMMBASE_ADDR_START;
+}
+
+/**
+ * mips_cdmm_setup() - Ensure the CDMM bus is initialised and usable.
+ * @bus:        Pointer to bus information for current CPU.
+ *              IS_ERR(bus) is checked, so no need for caller to check.
+ *
+ * The caller must prevent migration to another CPU, either by disabling
+ * pre-emption or by running from a pinned kernel thread.
+ *
+ * Returns      0 on success, -errno on failure.
+ */
+static int mips_cdmm_setup(struct mips_cdmm_bus *bus)
+{
+        unsigned long cdmmbase, flags;
+        int ret = 0;
+
+        if (IS_ERR(bus))
+                return PTR_ERR(bus);
+
+        local_irq_save(flags);
+        /* Don't set up bus a second time unless marked offline */
+        if (bus->offline) {
+                /* If CDMM region is still set up, nothing to do */
+                if (bus->phys == mips_cdmm_cur_base())
+                        goto out;
+                /*
+                 * The CDMM region isn't set up as expected, so it needs
+                 * reconfiguring, but then we can stop checking it.
+                 */
+                bus->offline = false;
+        } else if (bus->phys > 1) {
+                goto out;
+        }
+
+        /* If the CDMM region is already configured, inherit that setup */
+        if (!bus->phys)
+                bus->phys = mips_cdmm_cur_base();
+        /* Otherwise, ask platform code for suggestions */
+        if (!bus->phys && mips_cdmm_phys_base)
+                bus->phys = mips_cdmm_phys_base();
+        /* Otherwise, copy what other CPUs have done */
+        if (!bus->phys)
+                bus->phys = mips_cdmm_default_base;
+        /* Otherwise, complain once */
+        if (!bus->phys) {
+                bus->phys = 1;
+                /*
+                 * If you hit this, either your bootloader needs to set up the
+                 * CDMM on the boot CPU, or else you need to implement
+                 * mips_cdmm_phys_base() for your platform (see asm/cdmm.h).
+                 */
+                pr_err("cdmm%u: Failed to choose a physical base\n",
+                       smp_processor_id());
+        }
+        /* Already complained? */
+        if (bus->phys == 1) {
+                ret = -ENOMEM;
+                goto out;
+        }
+        /* Record our success for other CPUs to copy */
+        mips_cdmm_default_base = bus->phys;
+
+        pr_debug("cdmm%u: Enabling CDMM region at %pa\n",
+                 smp_processor_id(), &bus->phys);
+
+        /* Enable CDMM */
+        cdmmbase = read_c0_cdmmbase();
+        cdmmbase &= (1ul << MIPS_CDMMBASE_ADDR_SHIFT) - 1;
+        cdmmbase |= (bus->phys >> MIPS_CDMMBASE_ADDR_START)
+                        << MIPS_CDMMBASE_ADDR_SHIFT;
+        cdmmbase |= MIPS_CDMMBASE_EN;
+        write_c0_cdmmbase(cdmmbase);
+        tlbw_use_hazard();
+
+        bus->regs = (void __iomem *)CKSEG1ADDR(bus->phys);
+        bus->drbs = 1 + ((cdmmbase & MIPS_CDMMBASE_SIZE) >>
+                         MIPS_CDMMBASE_SIZE_SHIFT);
+        bus->drbs_reserved = !!(cdmmbase & MIPS_CDMMBASE_CI);
+
+out:
+        local_irq_restore(flags);
+        return ret;
+}
+
+/**
+ * mips_cdmm_early_probe() - Minimally probe for a specific device on CDMM.
+ * @dev_type:   CDMM type code to look for.
+ *
+ * Minimally configure the in-CPU Common Device Memory Map (CDMM) and look for a
+ * specific device. This can be used to find a device very early in boot for
+ * example to configure an early FDC console device.
+ *
+ * The caller must prevent migration to another CPU, either by disabling
+ * pre-emption or by running from a pinned kernel thread.
+ *
+ * Returns:     MMIO pointer to device memory. The caller can read the ACSR
+ *              register to find more information about the device (such as the
+ *              version number or the number of blocks).
+ *              May return IOMEM_ERR_PTR(-errno) in case of error, so check with
+ *              IS_ERR().
+ */
+void __iomem *mips_cdmm_early_probe(unsigned int dev_type)
+{
+        struct mips_cdmm_bus *bus;
+        void __iomem *cdmm;
+        u32 acsr;
+        unsigned int drb, type, size;
+        int err;
+
+        if (WARN_ON(!dev_type))
+                return IOMEM_ERR_PTR(-ENODEV);
+
+        bus = mips_cdmm_get_bus();
+        err = mips_cdmm_setup(bus);
+        if (err)
+                return IOMEM_ERR_PTR(err);
+
+        /* Skip the first block if it's reserved for more registers */
+        drb = bus->drbs_reserved;
+        cdmm = bus->regs;
+
+        /* Look for a specific device type */
+        for (; drb < bus->drbs; drb += size + 1) {
+                acsr = readl(cdmm + drb * CDMM_DRB_SIZE);
+                type = (acsr & CDMM_ACSR_DEVTYPE) >> CDMM_ACSR_DEVTYPE_SHIFT;
+                if (type == dev_type)
+                        return cdmm + drb * CDMM_DRB_SIZE;
+                size = (acsr & CDMM_ACSR_DEVSIZE) >> CDMM_ACSR_DEVSIZE_SHIFT;
+        }
+
+        return IOMEM_ERR_PTR(-ENODEV);
+}
+EXPORT_SYMBOL_GPL(mips_cdmm_early_probe);
+
+/**
+ * mips_cdmm_release() - Release a removed CDMM device.
+ * @dev:        Device object
+ *
+ * Clean up the struct mips_cdmm_device for an unused CDMM device. This is
+ * called automatically by the driver core when a device is removed.
+ */
+static void mips_cdmm_release(struct device *dev)
+{
+        struct mips_cdmm_device *cdev = to_mips_cdmm_device(dev);
+
+        kfree(cdev);
+}
+
+/**
+ * mips_cdmm_bus_discover() - Discover the devices on the CDMM bus.
+ * @bus:        CDMM bus information, must already be set up.
+ */
+static void mips_cdmm_bus_discover(struct mips_cdmm_bus *bus)
+{
+        void __iomem *cdmm;
+        u32 acsr;
+        unsigned int drb, type, size, rev;
+        struct mips_cdmm_device *dev;
+        unsigned int cpu = smp_processor_id();
+        int ret = 0;
+        int id = 0;
+
+        /* Skip the first block if it's reserved for more registers */
+        drb = bus->drbs_reserved;
+        cdmm = bus->regs;
+
+        /* Discover devices */
+        bus->discovered = true;
+        pr_info("cdmm%u discovery (%u blocks)\n", cpu, bus->drbs);
+        for (; drb < bus->drbs; drb += size + 1) {
+                acsr = readl(cdmm + drb * CDMM_DRB_SIZE);
+                type = (acsr & CDMM_ACSR_DEVTYPE) >> CDMM_ACSR_DEVTYPE_SHIFT;
+                size = (acsr & CDMM_ACSR_DEVSIZE) >> CDMM_ACSR_DEVSIZE_SHIFT;
+                rev  = (acsr & CDMM_ACSR_DEVREV)  >> CDMM_ACSR_DEVREV_SHIFT;
+
+                if (!type)
+                        continue;
+
+                pr_info("cdmm%u-%u: @%u (%#x..%#x), type 0x%02x, rev %u\n",
+                        cpu, id, drb, drb * CDMM_DRB_SIZE,
+                        (drb + size + 1) * CDMM_DRB_SIZE - 1,
+                        type, rev);
+
+                dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+                if (!dev)
+                        break;
+
+                dev->cpu = cpu;
+                dev->res.start = bus->phys + drb * CDMM_DRB_SIZE;
+                dev->res.end = bus->phys +
+                                (drb + size + 1) * CDMM_DRB_SIZE - 1;
+                dev->res.flags = IORESOURCE_MEM;
+                dev->type = type;
+                dev->rev = rev;
+                dev->dev.parent = get_cpu_device(cpu);
+                dev->dev.bus = &mips_cdmm_bustype;
+                dev->dev.id = atomic_inc_return(&mips_cdmm_next_id);
+                dev->dev.release = mips_cdmm_release;
+
+                dev_set_name(&dev->dev, "cdmm%u-%u", cpu, id);
+                ++id;
+                ret = device_register(&dev->dev);
+                if (ret) {
+                        put_device(&dev->dev);
+                        kfree(dev);
+                }
+        }
+}
+
+
+/*
+ * CPU hotplug and initialisation
+ *
+ * All the CDMM driver callbacks need to be executed on the appropriate CPU from
+ * workqueues. For the CPU callbacks, they need to be called for all devices on
+ * that CPU, so the work function calls bus_for_each_dev, using a helper
+ * (generated with BUILD_PERDEV_HELPER) to call the driver callback if the
+ * device's CPU matches.
+ */
+
+/**
+ * BUILD_PERDEV_HELPER() - Helper to call a CDMM driver callback if CPU matches.
+ * @_name:      Name of CDMM driver callback function.
+ *
+ * Generates a bus_for_each_dev callback function to call a specific CDMM driver
+ * callback function for the device if the device's CPU matches that pointed to
+ * by the data argument.
+ *
+ * This is used for informing drivers for all devices on a given CPU of some
+ * event (such as the CPU going online/offline).
+ *
+ * It is expected to already be called from the appropriate CPU.
+ */
+#define BUILD_PERDEV_HELPER(_name)                                      \
+static int mips_cdmm_##_name##_helper(struct device *dev, void *data)   \
+{                                                                       \
+        struct mips_cdmm_device *cdev = to_mips_cdmm_device(dev);       \
+        struct mips_cdmm_driver *cdrv;                                  \
+        unsigned int cpu = *(unsigned int *)data;                       \
+                                                                        \
+        if (cdev->cpu != cpu || !dev->driver)                           \
+                return 0;                                               \
+                                                                        \
+        cdrv = to_mips_cdmm_driver(dev->driver);                        \
+        if (!cdrv->_name)                                               \
+                return 0;                                               \
+        return cdrv->_name(cdev);                                       \
+}
+
+/* bus_for_each_dev callback helper functions */
+BUILD_PERDEV_HELPER(cpu_down)       /* int mips_cdmm_cpu_down_helper(...) */
+BUILD_PERDEV_HELPER(cpu_up)         /* int mips_cdmm_cpu_up_helper(...) */
+
+/**
+ * mips_cdmm_bus_down() - Tear down the CDMM bus.
+ * @data:       Pointer to unsigned int CPU number.
+ *
+ * This work_on_cpu callback function is executed on a given CPU to call the
+ * CDMM driver cpu_down callback for all devices on that CPU.
+ */
+static long mips_cdmm_bus_down(void *data)
+{
+        struct mips_cdmm_bus *bus;
+        long ret;
+
+        /* Inform all the devices on the bus */
+        ret = bus_for_each_dev(&mips_cdmm_bustype, NULL, data,
+                               mips_cdmm_cpu_down_helper);
+
+        /*
+         * While bus is offline, each use of it should reconfigure it just in
+         * case it is first use when coming back online again.
+         */
+        bus = mips_cdmm_get_bus();
+        if (!IS_ERR(bus))
+                bus->offline = true;
+
+        return ret;
+}
+
+/**
+ * mips_cdmm_bus_up() - Bring up the CDMM bus.
+ * @data:       Pointer to unsigned int CPU number.
+ *
+ * This work_on_cpu callback function is executed on a given CPU to discover
+ * CDMM devices on that CPU, or to call the CDMM driver cpu_up callback for all
+ * devices already discovered on that CPU.
+ *
+ * It is used during initialisation and when CPUs are brought online.
+ */
+static long mips_cdmm_bus_up(void *data)
+{
+        struct mips_cdmm_bus *bus;
+        long ret;
+
+        bus = mips_cdmm_get_bus();
+        ret = mips_cdmm_setup(bus);
+        if (ret)
+                return ret;
+
+        /* Bus now set up, so we can drop the offline flag if still set */
+        bus->offline = false;
+
+        if (!bus->discovered)
+                mips_cdmm_bus_discover(bus);
+        else
+                /* Inform all the devices on the bus */
+                ret = bus_for_each_dev(&mips_cdmm_bustype, NULL, data,
+                                       mips_cdmm_cpu_up_helper);
+
+        return ret;
+}
+
+/**
+ * mips_cdmm_cpu_notify() - Take action when a CPU is going online or offline.
+ * @nb:         CPU notifier block .
+ * @action:     Event that has taken place (CPU_*).
+ * @data:       CPU number.
+ *
+ * This notifier is used to keep the CDMM buses updated as CPUs are offlined and
+ * onlined. When CPUs go offline or come back online, so does their CDMM bus, so
+ * devices must be informed. Also when CPUs come online for the first time the
+ * devices on the CDMM bus need discovering.
+ *
+ * Returns:     NOTIFY_OK if event was used.
+ *              NOTIFY_DONE if we didn't care.
+ */
+static int mips_cdmm_cpu_notify(struct notifier_block *nb,
+                                unsigned long action, void *data)
+{
+        unsigned int cpu = (unsigned int)data;
+
+        switch (action & ~CPU_TASKS_FROZEN) {
+        case CPU_ONLINE:
+        case CPU_DOWN_FAILED:
+                work_on_cpu(cpu, mips_cdmm_bus_up, &cpu);
+                break;
+        case CPU_DOWN_PREPARE:
+                work_on_cpu(cpu, mips_cdmm_bus_down, &cpu);
+                break;
+        default:
+                return NOTIFY_DONE;
+        }
+
+        return NOTIFY_OK;
+}
+
+static struct notifier_block mips_cdmm_cpu_nb = {
+        .notifier_call = mips_cdmm_cpu_notify,
+};
+
+/**
+ * mips_cdmm_init() - Initialise CDMM bus.
+ *
+ * Initialise CDMM bus, discover CDMM devices for online CPUs, and arrange for
+ * hotplug notifications so the CDMM drivers can be kept up to date.
+ */
+static int __init mips_cdmm_init(void)
+{
+        unsigned int cpu;
+        int ret;
+
+        /* Register the bus */
+        ret = bus_register(&mips_cdmm_bustype);
+        if (ret)
+                return ret;
+
+        /* We want to be notified about new CPUs */
+        ret = register_cpu_notifier(&mips_cdmm_cpu_nb);
+        if (ret) {
+                pr_warn("cdmm: Failed to register CPU notifier\n");
+                goto out;
+        }
+
+        /* Discover devices on CDMM of online CPUs */
+        for_each_online_cpu(cpu)
+                work_on_cpu(cpu, mips_cdmm_bus_up, &cpu);
+
+        return 0;
+out:
+        bus_unregister(&mips_cdmm_bustype);
+        return ret;
+}
+subsys_initcall(mips_cdmm_init);
diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
index e530533b94be..3bfd56778c29 100644
--- a/include/linux/mod_devicetable.h
+++ b/include/linux/mod_devicetable.h
@@ -546,6 +546,14 @@ struct amba_id {
         void                    *data;
 };
 
+/**
+ * struct mips_cdmm_device_id - identifies devices in MIPS CDMM bus
+ * @type:       Device type identifier.
+ */
+struct mips_cdmm_device_id {
+        __u8    type;
+};
+
 /*
  * Match x86 CPUs for CPU specific drivers.
  * See documentation of "x86_match_cpu" for details.
diff --git a/scripts/mod/devicetable-offsets.c b/scripts/mod/devicetable-offsets.c
index f282516acc7b..fce36d0f6898 100644
--- a/scripts/mod/devicetable-offsets.c
+++ b/scripts/mod/devicetable-offsets.c
@@ -168,6 +168,9 @@ int main(void)
         DEVID_FIELD(amba_id, id);
         DEVID_FIELD(amba_id, mask);
 
+        DEVID(mips_cdmm_device_id);
+        DEVID_FIELD(mips_cdmm_device_id, type);
+
         DEVID(x86_cpu_id);
         DEVID_FIELD(x86_cpu_id, feature);
         DEVID_FIELD(x86_cpu_id, family);
diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
index e614ef689eee..78691d51a479 100644
--- a/scripts/mod/file2alias.c
+++ b/scripts/mod/file2alias.c
@@ -1109,6 +1109,22 @@ static int do_amba_entry(const char *filename,
 }
 ADD_TO_DEVTABLE("amba", amba_id, do_amba_entry);
 
+/*
+ * looks like: "mipscdmm:tN"
+ *
+ * N is exactly 2 digits, where each is an upper-case hex digit, or
+ *      a ? or [] pattern matching exactly one digit.
+ */
+static int do_mips_cdmm_entry(const char *filename,
+                              void *symval, char *alias)
+{
+        DEF_FIELD(symval, mips_cdmm_device_id, type);
+
+        sprintf(alias, "mipscdmm:t%02X*", type);
+        return 1;
+}
+ADD_TO_DEVTABLE("mipscdmm", mips_cdmm_device_id, do_mips_cdmm_entry);
+
 /* LOOKS like cpu:type:x86,venVVVVfamFFFFmodMMMM:feature:*,FEAT,*
  * All fields are numbers. It would be nicer to use strings for vendor
  * and feature, but getting those out of the build system here is too