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    SubjectRe: [PATCH 02/11 v3] drm/i915/intel_i2c: assign HDMI port D to pin pair 6
    On Mon, Mar 26, 2012 at 10:26:41PM +0800, Daniel Kurtz wrote:
    > 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.

    ... this is no longer true on drm-intel-next.

    > 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>

    Otherwise this looks ok to me - I've checked with gen3 Bspec and we seem
    to indeed have a 1:1 mapping, see "Display Registers", 1.5.3 "GPIO Control
    Registers", the list right below the heading.

    Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

    When resending, can you please add the Bspec reference above?

    Thanks, Daniel

    > ---
    > 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
    >

    --
    Daniel Vetter
    Mail: daniel@ffwll.ch
    Mobile: +41 (0)79 365 57 48


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