[Intel-gfx] [PATCH 2/2] drm/i915: make sure we write at least 32 DIP bytes

[Rodrigo Vivi]

I know almost nothing about hdmi infoframes, but isn't hdmi infoframes
limited to 30 bytes + 1 checksum byte?
(From HDMI Spec 8.2 section)

On Mon, Sep 24, 2012 at 10:32 AM, Paulo Zanoni <przanoni at gmail.com> wrote:
> From: Paulo Zanoni <paulo.r.zanoni at intel.com>
>
> If we don't write at least 32 DIP bytes the InfoFrame ECC may not be
> correctly calculated in some cases (e.g., when changing the port), and
> this will lead to black screens on HDMI monitors. The ECC value is
> generated by the hardware.
>
> I don't see how this should break anything since we're writing 0 and
> that should be the correct value, so this patch should be safe.
>
> This patch fixes bug #46761, which is marked as a regression
> introduced by commit 4e89ee174bb2da341bf90a84321c7008a3c9210d:
>     drm/i915: set the DIP port on ibx_write_infoframe
>
> Before commit 4e89 we were just failing to send AVI infoframes when we
> needed to change the port, which can lead to black screens in some
> cases. After commit 4e89 we started sending infoframes, but with a
> possibly wrong ECC value. After this patch I hope we start sending
> correct infoframes.
>
> Cc: stable at vger.kernel.org
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=46761
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_hdmi.c |   10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
> index f9fb47c..4ca355e 100644
> --- a/drivers/gpu/drm/i915/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> @@ -151,6 +151,8 @@ static void g4x_write_infoframe(struct drm_encoder *encoder,
>                 I915_WRITE(VIDEO_DIP_DATA, *data);
>                 data++;
>         }
> +       for (; i < 32; i += 4)
> +               I915_WRITE(VIDEO_DIP_DATA, 0);
>         mmiowb();
>
>         val |= g4x_infoframe_enable(frame);
> @@ -186,6 +188,8 @@ static void ibx_write_infoframe(struct drm_encoder *encoder,
>                 I915_WRITE(TVIDEO_DIP_DATA(intel_crtc->pipe), *data);
>                 data++;
>         }
> +       for (; i < 32; i += 4)
> +               I915_WRITE(TVIDEO_DIP_DATA(intel_crtc->pipe), 0);
>         mmiowb();
>
>         val |= g4x_infoframe_enable(frame);
> @@ -224,6 +228,8 @@ static void cpt_write_infoframe(struct drm_encoder *encoder,
>                 I915_WRITE(TVIDEO_DIP_DATA(intel_crtc->pipe), *data);
>                 data++;
>         }
> +       for (; i < 32; i += 4)
> +               I915_WRITE(TVIDEO_DIP_DATA(intel_crtc->pipe), 0);
>         mmiowb();
>
>         val |= g4x_infoframe_enable(frame);
> @@ -259,6 +265,8 @@ static void vlv_write_infoframe(struct drm_encoder *encoder,
>                 I915_WRITE(VLV_TVIDEO_DIP_DATA(intel_crtc->pipe), *data);
>                 data++;
>         }
> +       for (; i < 32; i += 4)
> +               I915_WRITE(VLV_TVIDEO_DIP_DATA(intel_crtc->pipe), 0);
>         mmiowb();
>
>         val |= g4x_infoframe_enable(frame);
> @@ -292,6 +300,8 @@ static void hsw_write_infoframe(struct drm_encoder *encoder,
>                 I915_WRITE(data_reg + i, *data);
>                 data++;
>         }
> +       for (; i < 32; i += 4)
> +               I915_WRITE(data_reg + i, 0);
>         mmiowb();
>
>         val |= hsw_infoframe_enable(frame);
> --
> 1.7.10.4
>
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-- 
Rodrigo Vivi
Blog: http://blog.vivi.eng.br