[Intel-gfx] [PATCH 6/9] drm/i915: Add a small adjustment to the pixel counter on interlaced modes

[akash goel]

Reviewed the patch & it looks good.
Just to confirm, this patch tries to address the case of a tiny window of
transition, i.e. from the 1st field (last half line) to 2nd field (first
half line).

Reviewed-by: "Akash Goel <akash.goels at gmail.com>"


On Tue, Apr 29, 2014 at 4:05 PM, <ville.syrjala at linux.intel.com> wrote:

> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
> In interlaced modes, the pixel counter counts all pixels,
> so one field will have htotal more pixels. In order to avoid
> the reported position from jumping backwards when the pixel
> counter is beyond the length of the shorter field, just
> clamp the position the length of the shorter field. This
> matches how the scanline counter based position works since
> the scanline counter doesn't count the two half lines.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_irq.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_irq.c
> b/drivers/gpu/drm/i915/i915_irq.c
> index 7e0d577..64cd888 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -844,6 +844,18 @@ static int i915_get_crtc_scanoutpos(struct drm_device
> *dev, int pipe,
>                 vtotal *= htotal;
>
>                 /*
> +                * In interlaced modes, the pixel counter counts all
> pixels,
> +                * so one field will have htotal more pixels. In order to
> avoid
> +                * the reported position from jumping backwards when the
> pixel
> +                * counter is beyond the length of the shorter field, just
> +                * clamp the position the length of the shorter field. This
> +                * matches how the scanline counter based position works
> since
> +                * the scanline counter doesn't count the two half lines.
> +                */
> +               if (position >= vtotal)
> +                       position = vtotal - 1;
> +
> +               /*
>                  * Start of vblank interrupt is triggered at start of
> hsync,
>                  * just prior to the first active line of vblank. However
> we
>                  * consider lines to start at the leading edge of
> horizontal
> --
> 1.8.3.2
>
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>
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