mfd: vexpress: Convert custom func API to regmap

Components of the Versatile Express platform (configuration
microcontrollers on motherboard and daughterboards in particular)
talk to each other over a custom configuration bus. They
provide miscellaneous functions (from clock generator control
to energy sensors) which are represented as platform devices
(and Device Tree nodes). The transactions on the bus can
be generated by different "bridges" in the system, some
of which are universal for the whole platform (for the price
of high transfer latencies), others restricted to a subsystem
(but much faster).

Until now drivers for such functions were using custom "func"
API, which is being replaced in this patch by regmap calls.
This required:

* a rework (and move to drivers/bus directory, as suggested
  by Samuel and Arnd) of the config bus core, which is much
  simpler now and uses device model infrastructure (class)
  to keep track of the bridges; non-DT case (soon to be
  retired anyway) is simply covered by a special device
  registration function

* the new config-bus driver also takes over device population,
  so there is no need for special matching table for
  of_platform_populate nor "simple-bus" hack in the arm64
  model dtsi file (relevant bindings documentation has
  been updated); this allows all the vexpress devices
  fit into normal device model, making it possible
  to remove plenty of early inits and other hacks in
  the near future

* adaptation of the syscfg bridge implementation in the
  sysreg driver, again making it much simpler; there is
  a special case of the "energy" function spanning two
  registers, where they should be both defined in the tree
  now, but backward compatibility is maintained in the code

* modification of the relevant drivers:

  * hwmon - just a straight-forward API change
  * power/reset driver - API change
  * regulator - API change plus error handling
    simplification
  * osc clock driver - this one required larger rework
    in order to turn in into a standard platform driver

Signed-off-by: Pawel Moll <pawel.moll@arm.com>
Acked-by: Mark Brown <broonie@linaro.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Mike Turquette <mturquette@linaro.org>

3 files changed, 213 insertions, 0 deletions

diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
index 552373c4e362..f24e79dd51bf 100644
--- a/drivers/bus/Kconfig
+++ b/drivers/bus/Kconfig
@@ -41,4 +41,13 @@ config ARM_CCI
         help
           Driver supporting the CCI cache coherent interconnect for ARM
           platforms.
+
+config VEXPRESS_CONFIG
+        bool "Versatile Express configuration bus"
+        default y if ARCH_VEXPRESS
+        depends on ARM || ARM64
+        select REGMAP
+        help
+          Platform configuration infrastructure for the ARM Ltd.
+          Versatile Express.
 endmenu
diff --git a/drivers/bus/Makefile b/drivers/bus/Makefile
index 8947bdd0de8b..f095aa771de9 100644
--- a/drivers/bus/Makefile
+++ b/drivers/bus/Makefile
@@ -10,3 +10,5 @@ obj-$(CONFIG_OMAP_OCP2SCP)	+= omap-ocp2scp.o
 obj-$(CONFIG_OMAP_INTERCONNECT) += omap_l3_smx.o omap_l3_noc.o
 # CCI cache coherent interconnect for ARM platforms
 obj-$(CONFIG_ARM_CCI)           += arm-cci.o
+
+obj-$(CONFIG_VEXPRESS_CONFIG)   += vexpress-config.o
diff --git a/drivers/bus/vexpress-config.c b/drivers/bus/vexpress-config.c
new file mode 100644
index 000000000000..27a07dfcd626
--- /dev/null
+++ b/drivers/bus/vexpress-config.c
@@ -0,0 +1,202 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * Copyright (C) 2014 ARM Limited
+ */
+
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/vexpress.h>
+
+
+struct vexpress_config_bridge {
+        struct vexpress_config_bridge_ops *ops;
+        void *context;
+};
+
+
+static DEFINE_MUTEX(vexpress_config_mutex);
+static struct class *vexpress_config_class;
+static u32 vexpress_config_site_master = VEXPRESS_SITE_MASTER;
+
+
+void vexpress_config_set_master(u32 site)
+{
+        vexpress_config_site_master = site;
+}
+
+u32 vexpress_config_get_master(void)
+{
+        return vexpress_config_site_master;
+}
+
+void vexpress_config_lock(void *arg)
+{
+        mutex_lock(&vexpress_config_mutex);
+}
+
+void vexpress_config_unlock(void *arg)
+{
+        mutex_unlock(&vexpress_config_mutex);
+}
+
+
+static void vexpress_config_find_prop(struct device_node *node,
+                const char *name, u32 *val)
+{
+        /* Default value */
+        *val = 0;
+
+        of_node_get(node);
+        while (node) {
+                if (of_property_read_u32(node, name, val) == 0) {
+                        of_node_put(node);
+                        return;
+                }
+                node = of_get_next_parent(node);
+        }
+}
+
+int vexpress_config_get_topo(struct device_node *node, u32 *site,
+                u32 *position, u32 *dcc)
+{
+        vexpress_config_find_prop(node, "arm,vexpress,site", site);
+        if (*site == VEXPRESS_SITE_MASTER)
+                *site = vexpress_config_site_master;
+        if (WARN_ON(vexpress_config_site_master == VEXPRESS_SITE_MASTER))
+                return -EINVAL;
+        vexpress_config_find_prop(node, "arm,vexpress,position", position);
+        vexpress_config_find_prop(node, "arm,vexpress,dcc", dcc);
+
+        return 0;
+}
+
+
+static void vexpress_config_devres_release(struct device *dev, void *res)
+{
+        struct vexpress_config_bridge *bridge = dev_get_drvdata(dev->parent);
+        struct regmap *regmap = res;
+
+        bridge->ops->regmap_exit(regmap, bridge->context);
+}
+
+struct regmap *devm_regmap_init_vexpress_config(struct device *dev)
+{
+        struct vexpress_config_bridge *bridge;
+        struct regmap *regmap;
+        struct regmap **res;
+
+        if (WARN_ON(dev->parent->class != vexpress_config_class))
+                return ERR_PTR(-ENODEV);
+
+        bridge = dev_get_drvdata(dev->parent);
+        if (WARN_ON(!bridge))
+                return ERR_PTR(-EINVAL);
+
+        res = devres_alloc(vexpress_config_devres_release, sizeof(*res),
+                        GFP_KERNEL);
+        if (!res)
+                return ERR_PTR(-ENOMEM);
+
+        regmap = bridge->ops->regmap_init(dev, bridge->context);
+        if (IS_ERR(regmap)) {
+                devres_free(res);
+                return regmap;
+        }
+
+        *res = regmap;
+        devres_add(dev, res);
+
+        return regmap;
+}
+
+
+struct device *vexpress_config_bridge_register(struct device *parent,
+                struct vexpress_config_bridge_ops *ops, void *context)
+{
+        struct device *dev;
+        struct vexpress_config_bridge *bridge;
+
+        if (!vexpress_config_class) {
+                vexpress_config_class = class_create(THIS_MODULE,
+                                "vexpress-config");
+                if (IS_ERR(vexpress_config_class))
+                        return (void *)vexpress_config_class;
+        }
+
+        dev = device_create(vexpress_config_class, parent, 0,
+                        NULL, "%s.bridge", dev_name(parent));
+
+        if (IS_ERR(dev))
+                return dev;
+
+        bridge = devm_kmalloc(dev, sizeof(*bridge), GFP_KERNEL);
+        if (!bridge) {
+                put_device(dev);
+                device_unregister(dev);
+                return ERR_PTR(-ENOMEM);
+        }
+        bridge->ops = ops;
+        bridge->context = context;
+
+        dev_set_drvdata(dev, bridge);
+
+        dev_dbg(parent, "Registered bridge '%s', parent node %p\n",
+                        dev_name(dev), parent->of_node);
+
+        return dev;
+}
+
+
+static int vexpress_config_node_match(struct device *dev, const void *data)
+{
+        const struct device_node *node = data;
+
+        dev_dbg(dev, "Parent node %p, looking for %p\n",
+                        dev->parent->of_node, node);
+
+        return dev->parent->of_node == node;
+}
+
+static int vexpress_config_populate(struct device_node *node)
+{
+        struct device_node *bridge;
+        struct device *parent;
+
+        bridge = of_parse_phandle(node, "arm,vexpress,config-bridge", 0);
+        if (!bridge)
+                return -EINVAL;
+
+        parent = class_find_device(vexpress_config_class, NULL, bridge,
+                        vexpress_config_node_match);
+        if (WARN_ON(!parent))
+                return -ENODEV;
+
+        return of_platform_populate(node, NULL, NULL, parent);
+}
+
+static int __init vexpress_config_init(void)
+{
+        int err = 0;
+        struct device_node *node;
+
+        /* Need the config devices early, before the "normal" devices... */
+        for_each_compatible_node(node, NULL, "arm,vexpress,config-bus") {
+                err = vexpress_config_populate(node);
+                if (err)
+                        break;
+        }
+
+        return err;
+}
+postcore_initcall(vexpress_config_init);
+