[Intel-gfx] [PATCH] drm/i915/skl: Increase cursor ddb blocks in multi-pipe config

[Runyan, Arthur J]

The bspec says "These are basic methods that can be used for single and multi-pipe modes. For optimal power usage, the display driver can choose to use more advanced allocation techniques as desired."
So we leave it up to the driver to optimize as it sees fit.

-----Original Message-----
From: Rodrigo Vivi [mailto:rodrigo.vivi at gmail.com] 
Sent: Thursday, June 16, 2016 4:20 PM
To: Sripada, Radhakrishna
Cc: intel-gfx; drm-intel-fixes at lists.freedesktop.org; Runyan, Arthur J
Subject: Re: [Intel-gfx] [PATCH] drm/i915/skl: Increase cursor ddb blocks in multi-pipe config

I believe we should use whatever BSpec recommends.

If that is not the best behavior and block things out than the spec needs to be updated or a workaround documented there.

Art? thoughts?

On Mon, Jun 13, 2016 at 3:03 PM, Radhakrishna Sripada <radhakrishna.sripada at intel.com> wrote:
> The bspec suggests giving cursor planes a fixed allocation of 8 blocks 
> when running in a multi-CRTC configuration.  However we have found 
> that this small allocation can only accommodate level
> 0 watermarks on many platforms, which in turn prevents the system from 
> entering deeper sleep states.  Let's use a slightly higher allocation 
> of 16 blocks for the cursor to increase our chances of enabling lower 
> power states.
>
> Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada at intel.com>
> Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c 
> b/drivers/gpu/drm/i915/intel_pm.c index 658a756..a949dac 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -2933,7 +2933,8 @@ static unsigned int skl_cursor_allocation(int num_active)
>         if (num_active == 1)
>                 return 32;
>
> -       return 8;
> +       /* higher than bspec recommendation (8) */
> +       return 16;
>  }
>
>  static void skl_ddb_entry_init_from_hw(struct skl_ddb_entry *entry, 
> u32 reg)
> --
> 1.9.1
>
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--
Rodrigo Vivi
Blog: http://blog.vivi.eng.br