[Intel-gfx] [PATCH] Lower threshold for pixel doubling.

[Stuart Abercrombie]

Any comments?

Without this, plugging one of the older Chromebook models into a Dell U3011
monitor produces a garbled display at the default 2048x1280 resolution.

The original threshold was apparently fairly arbitrary:

http://cgit.freedesktop.org/~anholt/xf86-video-intel/commit/?id=8fcf9a81179ee8577ddab5e904c58fbfd14cf59c
.

Stuart


On Mon, May 20, 2013 at 11:15 AM, Stuart Abercrombie <
sabercrombie at chromium.org> wrote:

> 90% of core speed (=180MHz dot clock) is too high for 2048x1280 to get
> pixel doubling on Pineview, which it needs to avoid underruns, so
> lower this to 85%.
>
> Signed-off-by: Stuart Abercrombie <sabercrombie at chromium.org>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c
> b/drivers/gpu/drm/i915/intel_display.c
> index efe8299..9c924e9 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -4564,14 +4564,14 @@ static void i9xx_set_pipeconf(struct intel_crtc
> *intel_crtc)
>         pipeconf = I915_READ(PIPECONF(intel_crtc->pipe));
>
>         if (intel_crtc->pipe == 0 && INTEL_INFO(dev)->gen < 4) {
> -               /* Enable pixel doubling when the dot clock is > 90% of
> the (display)
> +               /* Enable pixel doubling when the dot clock is > 85% of
> the (display)
>                  * core speed.
>                  *
>                  * XXX: No double-wide on 915GM pipe B. Is that the only
> reason for the
>                  * pipe == 0 check?
>                  */
>                 if (intel_crtc->config.requested_mode.clock >
> -                   dev_priv->display.get_display_clock_speed(dev) * 9 /
> 10)
> +                   dev_priv->display.get_display_clock_speed(dev) * 17 /
> 20)
>                         pipeconf |= PIPECONF_DOUBLE_WIDE;
>                 else
>                         pipeconf &= ~PIPECONF_DOUBLE_WIDE;
> --
> 1.8.2.1
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freedesktop.org/archives/intel-gfx/attachments/20130528/3bcfb8cc/attachment.html>