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@chromium.org --- drivers/gpu/drm/i915/i915_reg.h | 6 +++--- drivers/gpu/drm/i915/intel_i2c.c | 6 +++--- 2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h index 03c53fc..56af0df 100644 --- a/drivers/gpu/drm/i915/i915_reg.h +++ b/drivers/gpu/drm/i915/i915_reg.h @@ -697,9 +697,9 @@ #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 5e413c4..1135e3e 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/drivers/gpu/drm/i915/intel_i2c.c @@ -157,8 +157,8 @@ intel_gpio_create(struct drm_i915_private *dev_priv, u32 pin) GPIOC, GPIOD, GPIOE, - 0, GPIOF, + 0, }; struct intel_gpio *gpio;
@@ -175,7 +175,7 @@ intel_gpio_create(struct drm_i915_private *dev_priv, u32 pin) gpio->dev_priv = dev_priv;
snprintf(gpio->adapter.name, sizeof(gpio->adapter.name), - "i915 GPIO%c", "?BACDE?F"[pin]); + "i915 GPIO%c", "?BACDEF?"[pin]); gpio->adapter.owner = THIS_MODULE; gpio->adapter.algo_data = &gpio->algo; gpio->adapter.dev.parent = &dev_priv->dev->pdev->dev; @@ -376,8 +376,8 @@ 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;