i2c: piix4: Add support for multiplexed main adapter in SB800

The SB800 chipset supports a multiplexed main SMBus controller with
four ports. The multiplexed ports share the same SMBus address and
register set. The port is selected by bits 2:1 of the smb_en register
(0x2C).

Only one port can be active at any point in time therefore a mutex is
needed in order to synchronize access.

Additionally, the commit avoids requesting and releasing the SMBus base
address index region on every multiplexed transfer by moving the
request_region call into piix4_probe.

Tested on HP ProLiant MicroServer G7 N54L (where this patch adds
support to access sensor data from the w83795adg).

Cc: Thomas Brandon <tbrandonau@gmail.com>
Cc: Eddi De Pieri <eddi@depieri.net>
Signed-off-by: Christian Fetzer <fetzer.ch@gmail.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

1 files changed, 147 insertions, 22 deletions

diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c
index 9c32eb124b72..6b4231d406d5 100644
--- a/drivers/i2c/busses/i2c-piix4.c
+++ b/drivers/i2c/busses/i2c-piix4.c
@@ -23,6 +23,9 @@
 
    Note: we assume there can only be one device, with one or more
    SMBus interfaces.
+   The device can register multiple i2c_adapters (up to PIIX4_MAX_ADAPTERS).
+   For devices supporting multiple ports the i2c_adapter should provide
+   an i2c_algorithm to access them.
 */
 
 #include <linux/module.h>
@@ -37,6 +40,7 @@
 #include <linux/dmi.h>
 #include <linux/acpi.h>
 #include <linux/io.h>
+#include <linux/mutex.h>
 
 
 /* PIIX4 SMBus address offsets */
@@ -78,6 +82,13 @@
 /* Multi-port constants */
 #define PIIX4_MAX_ADAPTERS 4
 
+/* SB800 constants */
+#define SB800_PIIX4_SMB_IDX             0xcd6
+
+/* SB800 port is selected by bits 2:1 of the smb_en register (0x2c) */
+#define SB800_PIIX4_PORT_IDX            0x2c
+#define SB800_PIIX4_PORT_IDX_MASK       0x06
+
 /* insmod parameters */
 
 /* If force is set to anything different from 0, we forcibly enable the
@@ -127,6 +138,11 @@ static const struct dmi_system_id piix4_dmi_ibm[] = {
 
 struct i2c_piix4_adapdata {
         unsigned short smba;
+
+        /* SB800 */
+        bool sb800_main;
+        unsigned short port;
+        struct mutex *mutex;
 };
 
 static int piix4_setup(struct pci_dev *PIIX4_dev,
@@ -232,7 +248,6 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
                              const struct pci_device_id *id, u8 aux)
 {
         unsigned short piix4_smba;
-        unsigned short smba_idx = 0xcd6;
         u8 smba_en_lo, smba_en_hi, smb_en, smb_en_status;
         u8 i2ccfg, i2ccfg_offset = 0x10;
 
@@ -254,16 +269,10 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
         else
                 smb_en = (aux) ? 0x28 : 0x2c;
 
-        if (!request_region(smba_idx, 2, "smba_idx")) {
-                dev_err(&PIIX4_dev->dev, "SMBus base address index region "
-                        "0x%x already in use!\n", smba_idx);
-                return -EBUSY;
-        }
-        outb_p(smb_en, smba_idx);
-        smba_en_lo = inb_p(smba_idx + 1);
-        outb_p(smb_en + 1, smba_idx);
-        smba_en_hi = inb_p(smba_idx + 1);
-        release_region(smba_idx, 2);
+        outb_p(smb_en, SB800_PIIX4_SMB_IDX);
+        smba_en_lo = inb_p(SB800_PIIX4_SMB_IDX + 1);
+        outb_p(smb_en + 1, SB800_PIIX4_SMB_IDX);
+        smba_en_hi = inb_p(SB800_PIIX4_SMB_IDX + 1);
 
         if (!smb_en) {
                 smb_en_status = smba_en_lo & 0x10;
@@ -527,6 +536,43 @@ static s32 piix4_access(struct i2c_adapter * adap, u16 addr,
         return 0;
 }
 
+/*
+ * Handles access to multiple SMBus ports on the SB800.
+ * The port is selected by bits 2:1 of the smb_en register (0x2c).
+ * Returns negative errno on error.
+ *
+ * Note: The selected port must be returned to the initial selection to avoid
+ * problems on certain systems.
+ */
+static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
+                 unsigned short flags, char read_write,
+                 u8 command, int size, union i2c_smbus_data *data)
+{
+        struct i2c_piix4_adapdata *adapdata = i2c_get_adapdata(adap);
+        u8 smba_en_lo;
+        u8 port;
+        int retval;
+
+        mutex_lock(adapdata->mutex);
+
+        outb_p(SB800_PIIX4_PORT_IDX, SB800_PIIX4_SMB_IDX);
+        smba_en_lo = inb_p(SB800_PIIX4_SMB_IDX + 1);
+
+        port = adapdata->port;
+        if ((smba_en_lo & SB800_PIIX4_PORT_IDX_MASK) != (port << 1))
+                outb_p((smba_en_lo & ~SB800_PIIX4_PORT_IDX_MASK) | (port << 1),
+                       SB800_PIIX4_SMB_IDX + 1);
+
+        retval = piix4_access(adap, addr, flags, read_write,
+                              command, size, data);
+
+        outb_p(smba_en_lo, SB800_PIIX4_SMB_IDX + 1);
+
+        mutex_unlock(adapdata->mutex);
+
+        return retval;
+}
+
 static u32 piix4_func(struct i2c_adapter *adapter)
 {
         return I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
@@ -539,6 +585,11 @@ static const struct i2c_algorithm smbus_algorithm = {
         .functionality  = piix4_func,
 };
 
+static const struct i2c_algorithm piix4_smbus_algorithm_sb800 = {
+        .smbus_xfer     = piix4_access_sb800,
+        .functionality  = piix4_func,
+};
+
 static const struct pci_device_id piix4_ids[] = {
         { PCI_DEVICE(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371AB_3) },
         { PCI_DEVICE(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82443MX_3) },
@@ -614,6 +665,53 @@ static int piix4_add_adapter(struct pci_dev *dev, unsigned short smba,
         return 0;
 }
 
+static int piix4_add_adapters_sb800(struct pci_dev *dev, unsigned short smba)
+{
+        struct mutex *mutex;
+        struct i2c_piix4_adapdata *adapdata;
+        int port;
+        int retval;
+
+        mutex = kzalloc(sizeof(*mutex), GFP_KERNEL);
+        if (mutex == NULL)
+                return -ENOMEM;
+
+        mutex_init(mutex);
+
+        for (port = 0; port < PIIX4_MAX_ADAPTERS; port++) {
+                retval = piix4_add_adapter(dev, smba,
+                                           &piix4_main_adapters[port]);
+                if (retval < 0)
+                        goto error;
+
+                piix4_main_adapters[port]->algo = &piix4_smbus_algorithm_sb800;
+
+                adapdata = i2c_get_adapdata(piix4_main_adapters[port]);
+                adapdata->sb800_main = true;
+                adapdata->port = port;
+                adapdata->mutex = mutex;
+        }
+
+        return retval;
+
+error:
+        dev_err(&dev->dev,
+                "Error setting up SB800 adapters. Unregistering!\n");
+        while (--port >= 0) {
+                adapdata = i2c_get_adapdata(piix4_main_adapters[port]);
+                if (adapdata->smba) {
+                        i2c_del_adapter(piix4_main_adapters[port]);
+                        kfree(adapdata);
+                        kfree(piix4_main_adapters[port]);
+                        piix4_main_adapters[port] = NULL;
+                }
+        }
+
+        kfree(mutex);
+
+        return retval;
+}
+
 static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
 {
         int retval;
@@ -621,20 +719,41 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
         if ((dev->vendor == PCI_VENDOR_ID_ATI &&
              dev->device == PCI_DEVICE_ID_ATI_SBX00_SMBUS &&
              dev->revision >= 0x40) ||
-            dev->vendor == PCI_VENDOR_ID_AMD)
+            dev->vendor == PCI_VENDOR_ID_AMD) {
+                if (!request_region(SB800_PIIX4_SMB_IDX, 2, "smba_idx")) {
+                        dev_err(&dev->dev,
+                        "SMBus base address index region 0x%x already in use!\n",
+                        SB800_PIIX4_SMB_IDX);
+                        return -EBUSY;
+                }
+
                 /* base address location etc changed in SB800 */
                 retval = piix4_setup_sb800(dev, id, 0);
-        else
-                retval = piix4_setup(dev, id);
+                if (retval < 0) {
+                        release_region(SB800_PIIX4_SMB_IDX, 2);
+                        return retval;
+                }
 
-        /* If no main SMBus found, give up */
-        if (retval < 0)
-                return retval;
+                /*
+                 * Try to register multiplexed main SMBus adapter,
+                 * give up if we can't
+                 */
+                retval = piix4_add_adapters_sb800(dev, retval);
+                if (retval < 0) {
+                        release_region(SB800_PIIX4_SMB_IDX, 2);
+                        return retval;
+                }
+        } else {
+                retval = piix4_setup(dev, id);
+                if (retval < 0)
+                        return retval;
 
-        /* Try to register main SMBus adapter, give up if we can't */
-        retval = piix4_add_adapter(dev, retval, &piix4_main_adapters[0]);
-        if (retval < 0)
-                return retval;
+                /* Try to register main SMBus adapter, give up if we can't */
+                retval = piix4_add_adapter(dev, retval,
+                                           &piix4_main_adapters[0]);
+                if (retval < 0)
+                        return retval;
+        }
 
         /* Check for auxiliary SMBus on some AMD chipsets */
         retval = -ENODEV;
@@ -669,7 +788,13 @@ static void piix4_adap_remove(struct i2c_adapter *adap)
 
         if (adapdata->smba) {
                 i2c_del_adapter(adap);
-                release_region(adapdata->smba, SMBIOSIZE);
+                if (adapdata->port == 0) {
+                        release_region(adapdata->smba, SMBIOSIZE);
+                        if (adapdata->sb800_main) {
+                                kfree(adapdata->mutex);
+                                release_region(SB800_PIIX4_SMB_IDX, 2);
+                        }
+                }
                 kfree(adapdata);
                 kfree(adap);
         }