drm/i915/intel_i2c: gmbus disabled and reserved ports are invalid

There is no GMBUS "disabled" port 0, nor "reserved" port 7.
For the other 6 ports there is a fixed 1:1 mapping between pin pairs and
gmbus ports, which means every real gmbus port has a gpio pin.

Given these realizations, clean up gmbus initialization.

Tested on Sandybridge (gen 6, PCH == CougarPoint) hardware.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

3 files changed, 29 insertions, 46 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 44e6430af3d4..c5ad7b96b065 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -303,7 +303,6 @@ struct intel_fbc_work;
 struct intel_gmbus {
         struct i2c_adapter adapter;
         bool force_bit;
-        bool has_gpio;
         u32 reg0;
         u32 gpio_reg;
         struct i2c_algo_bit_data bit_algo;
@@ -1344,7 +1343,7 @@ extern int intel_setup_gmbus(struct drm_device *dev);
 extern void intel_teardown_gmbus(struct drm_device *dev);
 extern inline bool intel_gmbus_is_port_valid(unsigned port)
 {
-        return (port >= GMBUS_PORT_DISABLED && port <= GMBUS_PORT_RESERVED);
+        return (port >= GMBUS_PORT_SSC && port <= GMBUS_PORT_DPD);
 }
 
 extern struct i2c_adapter *intel_gmbus_get_adapter(
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index accd8ee48f9d..a8d218ca7d1d 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -744,7 +744,7 @@
 #define   GMBUS_PORT_DPB        5 /* SDVO, HDMIB */
 #define   GMBUS_PORT_DPD        6 /* HDMID */
 #define   GMBUS_PORT_RESERVED   7 /* 7 reserved */
-#define   GMBUS_NUM_PORTS       8
+#define   GMBUS_NUM_PORTS       (GMBUS_PORT_DPD - GMBUS_PORT_SSC + 1)
 #define GMBUS1                  0x5104 /* command/status */
 #define   GMBUS_SW_CLR_INT      (1<<31)
 #define   GMBUS_SW_RDY          (1<<30)
diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index 2f65d01340ff..dcde6f64777a 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -35,6 +35,20 @@
 #include "i915_drm.h"
 #include "i915_drv.h"
 
+struct gmbus_port {
+        const char *name;
+        int reg;
+};
+
+static const struct gmbus_port gmbus_ports[] = {
+        { "ssc", GPIOB },
+        { "vga", GPIOA },
+        { "panel", GPIOC },
+        { "dpc", GPIOD },
+        { "dpb", GPIOE },
+        { "dpd", GPIOF },
+};
+
 /* Intel GPIO access functions */
 
 #define I2C_RISEFALL_TIME 10
@@ -166,29 +180,16 @@ intel_gpio_post_xfer(struct i2c_adapter *adapter)
         intel_i2c_quirk_set(dev_priv, false);
 }
 
-static bool
+static void
 intel_gpio_setup(struct intel_gmbus *bus, u32 pin)
 {
         struct drm_i915_private *dev_priv = bus->dev_priv;
-        static const int map_pin_to_reg[] = {
-                0,
-                GPIOB,
-                GPIOA,
-                GPIOC,
-                GPIOD,
-                GPIOE,
-                GPIOF,
-                0,
-        };
         struct i2c_algo_bit_data *algo;
 
-        if (pin >= ARRAY_SIZE(map_pin_to_reg) || !map_pin_to_reg[pin])
-                return false;
-
         algo = &bus->bit_algo;
 
-        bus->gpio_reg = map_pin_to_reg[pin];
-        bus->gpio_reg += dev_priv->gpio_mmio_base;
+        /* -1 to map pin pair to gmbus index */
+        bus->gpio_reg = dev_priv->gpio_mmio_base + gmbus_ports[pin - 1].reg;
 
         bus->adapter.algo_data = algo;
         algo->setsda = set_data;
@@ -200,8 +201,6 @@ intel_gpio_setup(struct intel_gmbus *bus, u32 pin)
         algo->udelay = I2C_RISEFALL_TIME;
         algo->timeout = usecs_to_jiffies(2200);
         algo->data = bus;
-
-        return true;
 }
 
 static int
@@ -351,15 +350,9 @@ timeout:
                  bus->adapter.name, bus->reg0 & 0xff);
         I915_WRITE(GMBUS0 + reg_offset, 0);
 
-        /* Hardware may not support GMBUS over these pins?
-         * Try GPIO bitbanging instead.
-         */
-        if (!bus->has_gpio) {
-                ret = -EIO;
-        } else {
-                bus->force_bit = true;
-                ret = i2c_bit_algo.master_xfer(adapter, msgs, num);
-        }
+        /* Hardware may not support GMBUS over these pins? Try GPIO bitbanging instead. */
+        bus->force_bit = true;
+        ret = i2c_bit_algo.master_xfer(adapter, msgs, num);
 
 out:
         mutex_unlock(&dev_priv->gmbus_mutex);
@@ -386,16 +379,6 @@ static const struct i2c_algorithm gmbus_algorithm = {
  */
 int intel_setup_gmbus(struct drm_device *dev)
 {
-        static const char *names[GMBUS_NUM_PORTS] = {
-                "disabled",
-                "ssc",
-                "vga",
-                "panel",
-                "dpc",
-                "dpb",
-                "dpd",
-                "reserved",
-        };
         struct drm_i915_private *dev_priv = dev->dev_private;
         int ret, i;
 
@@ -413,13 +396,14 @@ int intel_setup_gmbus(struct drm_device *dev)
 
         for (i = 0; i < GMBUS_NUM_PORTS; i++) {
                 struct intel_gmbus *bus = &dev_priv->gmbus[i];
+                u32 port = i + 1; /* +1 to map gmbus index to pin pair */
 
                 bus->adapter.owner = THIS_MODULE;
                 bus->adapter.class = I2C_CLASS_DDC;
                 snprintf(bus->adapter.name,
                          sizeof(bus->adapter.name),
                          "i915 gmbus %s",
-                         names[i]);
+                         gmbus_ports[i].name);
 
                 bus->adapter.dev.parent = &dev->pdev->dev;
                 bus->dev_priv = dev_priv;
@@ -430,9 +414,9 @@ int intel_setup_gmbus(struct drm_device *dev)
                         goto err;
 
                 /* By default use a conservative clock rate */
-                bus->reg0 = i | GMBUS_RATE_100KHZ;
+                bus->reg0 = port | GMBUS_RATE_100KHZ;
 
-                bus->has_gpio = intel_gpio_setup(bus, i);
+                intel_gpio_setup(bus, port);
         }
 
         intel_i2c_reset(dev_priv->dev);
@@ -453,8 +437,9 @@ struct i2c_adapter *intel_gmbus_get_adapter(struct drm_i915_private *dev_priv,
                                             unsigned port)
 {
         WARN_ON(!intel_gmbus_is_port_valid(port));
+        /* -1 to map pin pair to gmbus index */
         return (intel_gmbus_is_port_valid(port)) ?
-                &dev_priv->gmbus[port].adapter : NULL;
+                &dev_priv->gmbus[port - 1].adapter : NULL;
 }
 
 void intel_gmbus_set_speed(struct i2c_adapter *adapter, int speed)
@@ -468,8 +453,7 @@ void intel_gmbus_force_bit(struct i2c_adapter *adapter, bool force_bit)
 {
         struct intel_gmbus *bus = to_intel_gmbus(adapter);
 
-        if (bus->has_gpio)
-                bus->force_bit = force_bit;
+        bus->force_bit = force_bit;
 }
 
 void intel_teardown_gmbus(struct drm_device *dev)