[Intel-gfx] [PATCH] CHROMIUM: drm/i915/intel_i2c: enable 400kHz GMBUS for atmel_mxt devices

[james.ausmus at intel.com]

From: Daniel Kurtz <djkurtz at chromium.org>

i915 gmbus writes at 400kHz should now work properly.

So, enable 400kHz and the native gmbus algorithm by default, but limit
to known high speed devices:
  * atmel_mxt devices on vga ddc
  * atmel_mxt devices (app mode and bootloader) on panel ddc

After further testing, this can be enabled for all devices and ddc
adapters.

Signed-off-by: Daniel Kurtz <djkurtz at chromium.org>

BUG=chromium-os:26118,chrome-os-partner:8547,chrome-os-partner:8732
TEST=compiles clean; i915 driver successfully communicates to i2c devices
  on the vga and panel ddc adapters.
  Tested using an atmel i2c touchpad and atmel_mxt_ts driver.
TEST=place valid atmel mxt firmware at /lib/firmware/maxtouch.fw
  time echo 1 > update_fw
  Check that firmware update succeeds, and that the time is less than 18s.
  time echo 1 > update_fw

  real	0m17.923s
  user	0m0.000s
  sys	0m0.188s

This is a squash of three commits onto v3.4-rc5+danvet/intel-drm-next:

Change-Id: Id911a732409b06a4b0a654270d548929e2887582
Reviewed-on: https://gerrit.chromium.org/gerrit/17938

Change-Id: Ide237fbe6c33b17395d8398af1b691db69eb3036
Reviewed-on: https://gerrit.chromium.org/gerrit/18425

Change-Id: Ic5741b98b30c522acd3bee0a92041e08993e950e
Reviewed-on: https://gerrit.chromium.org/gerrit/21833
---
 drivers/gpu/drm/i915/i915_reg.h  |  2 ++
 drivers/gpu/drm/i915/intel_i2c.c | 10 +++++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 59afb7e..27ef35a 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -865,6 +865,7 @@
 #define   GMBUS_RATE_50KHZ	(1<<8)
 #define   GMBUS_RATE_400KHZ	(2<<8) /* reserved on Pineview */
 #define   GMBUS_RATE_1MHZ	(3<<8) /* reserved on Pineview */
+#define   GMBUS_RATE_MASK	(3<<8)
 #define   GMBUS_HOLD_EXT	(1<<7) /* 300ns hold time, rsvd on Pineview */
 #define   GMBUS_PORT_DISABLED	0
 #define   GMBUS_PORT_SSC	1
@@ -875,6 +876,7 @@
 #define   GMBUS_PORT_DPD	6 /* HDMID */
 #define   GMBUS_PORT_RESERVED	7 /* 7 reserved */
 #define   GMBUS_NUM_PORTS	(GMBUS_PORT_DPD - GMBUS_PORT_SSC + 1)
+#define   GMBUS_PORT_MASK	7
 #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 3ef5af1..364204f 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -332,6 +332,7 @@ gmbus_xfer(struct i2c_adapter *adapter,
 	struct drm_i915_private *dev_priv = bus->dev_priv;
 	int i, reg_offset;
 	int ret = 0;
+	u32 gmbus0;
 
 	mutex_lock(&dev_priv->gmbus_mutex);
 
@@ -342,7 +343,14 @@ gmbus_xfer(struct i2c_adapter *adapter,
 
 	reg_offset = dev_priv->gpio_mmio_base;
 
-	I915_WRITE(GMBUS0 + reg_offset, bus->reg0);
+	/* Hack to use 400kHz only for atmel_mxt i2c devices on ddc ports */
+	gmbus0 = bus->reg0;
+	if (((gmbus0 & GMBUS_PORT_MASK) == GMBUS_PORT_VGADDC &&
+	     msgs[0].addr == 0x4b) ||
+	    ((gmbus0 & GMBUS_PORT_MASK) == GMBUS_PORT_PANEL &&
+	     (msgs[0].addr == 0x4a || msgs[0].addr == 0x26)))
+		gmbus0 = (gmbus0 & ~GMBUS_RATE_MASK) | GMBUS_RATE_400KHZ;
+	I915_WRITE(GMBUS0 + reg_offset, gmbus0);
 
 	for (i = 0; i < num; i++) {
 		u32 gmbus2;
-- 
1.8.3.2