On Wed, Nov 14, 2018 at 11:07:21PM +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrj...@linux.intel.com>
>
> If the level 0 latency is 0 we can't do anything. Return an error
> rather than success.
>
> While this can't happen due to WaWmMemoryReadLatency, it can
> happen if the user clears out the level 0 latency via debugfs.
>
> v2: Clarify how how we can end here with zero level 0 latency (Matt)
>
> Cc: Matt Roper <matthew.d.ro...@intel.com>
> Reviewed-by: Rodrigo Vivi <rodrigo.v...@intel.com>
> Signed-off-by: Ville Syrjälä <ville.syrj...@linux.intel.com>
I wonder whether we should really be letting users shoot themselves in
the foot with debugfs here. Maybe we should pull the sanitization and
hardware workarounds out of intel_read_wm_latency() and also apply it to
whatever debugfs gives us.
This is good enough for now though.
Reviewed-by: Matt Roper <matthew.d.ro...@intel.com>
> ---
> drivers/gpu/drm/i915/intel_pm.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 27498ded4949..25f589c4f68c 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -4704,8 +4704,10 @@ static int skl_compute_plane_wm(const struct
> drm_i915_private *dev_priv,
> bool apply_memory_bw_wa = skl_needs_memory_bw_wa(state);
> uint32_t min_disp_buf_needed;
>
> - if (latency == 0 ||
> - !intel_wm_plane_visible(cstate, intel_pstate)) {
> + if (latency == 0)
> + return level == 0 ? -EINVAL : 0;
> +
> + if (!intel_wm_plane_visible(cstate, intel_pstate)) {
> result->plane_en = false;
> return 0;
> }
> --
> 2.18.1
>
--
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795
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