According to i915 documentation [1], "Port D" (DP/HDMI Port D) is actually gmbus pin pair 6 (gmbus0.2:0 == 110b GPIOF), not 7 (111b). Pin pair 7 is a reserved pair.
[1] Documentation for [DevSNB+] and [DevIBX], as found on http://intellinuxgraphics.org Note: the "reserved" and "disabled" pairs do not actually map to a physical pair of pins, nor GPIO regs and shouldn't be initialized or used. Fixing this is left for a later patch. This bug has not been noticed for two reasons: 1) "gmbus" mode is currently disabled - all transfers are actually using "bit-bang" mode which uses the GPIO port 5 (the "HDMI/DPD CTLDATA/CLK" pair), at register 0x5024 (defined as GPIOF i915_reg.h). Since this is the correct pair of pins for HDMI1, transfers succeed. 2) Even if gmbus mode is re-enabled, the first attempted transaction will fail because it tries to use the wrong ("Reserved") pin pair. However, the driver immediately falls back again to the bit-bang method, which correctly uses GPIOF, so again, transfers succeed. However, if gmbus mode is re-enabled and the GPIO fall-back mode is disabled, then reading an attached monitor's EDID fail. Signed-off-by: Daniel Kurtz <djkurtz at chromium.org> --- drivers/gpu/drm/i915/i915_reg.h | 6 +++--- drivers/gpu/drm/i915/intel_i2c.c | 4 ++-- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h index f3609f2..accd8ee 100644 --- a/drivers/gpu/drm/i915/i915_reg.h +++ b/drivers/gpu/drm/i915/i915_reg.h @@ -742,9 +742,9 @@ #define GMBUS_PORT_PANEL 3 #define GMBUS_PORT_DPC 4 /* HDMIC */ #define GMBUS_PORT_DPB 5 /* SDVO, HDMIB */ - /* 6 reserved */ -#define GMBUS_PORT_DPD 7 /* HDMID */ -#define GMBUS_NUM_PORTS 8 +#define GMBUS_PORT_DPD 6 /* HDMID */ +#define GMBUS_PORT_RESERVED 7 /* 7 reserved */ +#define GMBUS_NUM_PORTS 8 #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 86b1861..54f85a1 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/drivers/gpu/drm/i915/intel_i2c.c @@ -148,8 +148,8 @@ intel_gpio_setup(struct intel_gmbus *bus, u32 pin) GPIOC, GPIOD, GPIOE, - 0, GPIOF, + 0, }; struct i2c_algo_bit_data *algo; @@ -359,8 +359,8 @@ int intel_setup_gmbus(struct drm_device *dev) "panel", "dpc", "dpb", - "reserved", "dpd", + "reserved", }; struct drm_i915_private *dev_priv = dev->dev_private; int ret, i; -- 1.7.7.3
