[Intel-gfx] [PATCH] drm/i915: Fix big cursors on snb

[Daniel Vetter]

Forgotten to cc Art as fyi.
-Daniel

On Mon, Mar 2, 2015 at 5:35 PM, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> My snb seemed somewhat unhappy with 256x256 cursors and failed all the
> relevant kms_cursor_crc subtests sporadically, including logging cpu
> fifo underruns. Smaller cursor work perfectly with a failure rate at
> least 1000x less (got bored after running tests for days).
>
> After some playing around with impressive hammers Ville suggested to
> increase the watermarks to at least cover a full cursor line. It seems
> to work thus far. This means that for lp wms we now required 1/4th of
> the fifo for 256 wide cursors, and much less on gen7+. Hence fetches
> should still be nice&big. Therefore I expect very little power impact
> and decided to just do this everywhere, even though I've only seen
> this on my snb laptop. Especially since Ville is thinking about
> similar changes for the gmch wm code. skl separate wm code and also
> completely new plane hw, so hopefully isn't affected.
>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: Matt Roper <matthew.d.roper at intel.com>
> Cc: Paulo Zanoni <przanoni at gmail.com>
> Testcase: igt/kms_cursor_crc/*-256x256-*
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 7dcb5b60600b..7e97a30bd6c0 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -1449,14 +1449,21 @@ static uint32_t ilk_compute_spr_wm(const struct ilk_pipe_wm_parameters *params,
>  static uint32_t ilk_compute_cur_wm(const struct ilk_pipe_wm_parameters *params,
>                                    uint32_t mem_value)
>  {
> +       uint32_t line_wm, method2;
> +
>         if (!params->active || !params->cur.enabled)
>                 return 0;
>
> -       return ilk_wm_method2(params->pixel_rate,
> -                             params->pipe_htotal,
> -                             params->cur.horiz_pixels,
> -                             params->cur.bytes_per_pixel,
> -                             mem_value);
> +       /* HACK: Big cursors tend to underrun, load at least one line. */
> +       line_wm = params->cur.horiz_pixels * params->cur.bytes_per_pixel / 64;
> +
> +       method2 = ilk_wm_method2(params->pixel_rate,
> +                                params->pipe_htotal,
> +                                params->cur.horiz_pixels,
> +                                params->cur.bytes_per_pixel,
> +                                mem_value);
> +
> +       return max(line_wm, method2);
>  }
>
>  /* Only for WM_LP. */
> --
> 1.9.3
>



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch