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Subject[PATCH 02/10 v2] drm/i915/intel_i2c: assign HDMI port D to pin pair 6
Date
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;
--
1.7.7.3


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