Re: [PATCH] drm/i915/: Initialise trans_min for skl_compute_transition_wm()

Mahesh Kumar
2017-11-08T05:06:57Z

Hi,

On Tuesday 07 November 2017 11:57 PM, Chris Wilson wrote:
> clang spots
>
> drivers/gpu/drm/i915/intel_pm.c:4655:6: warning: variable 'trans_min' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
> if (INTEL_GEN(dev_priv) >= 10)
>
> but fortunately for us we skip the function unless on a gen10+ device.
> However, to keep the function generic in case we do want to re-enable it
> for gen9 again, initialise trans_min to 0.
>
> References: ca47667f523e ("drm/i915/gen10: Calculate and enable transition WM")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Mahesh Kumar <mahesh1.kumar@intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
> drivers/gpu/drm/i915/intel_pm.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index b75c4cf074ff..40da5001be28 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -4652,6 +4652,7 @@ static void skl_compute_transition_wm(struct intel_crtc_state *cstate,
> if (!dev_priv->ipc_enabled)
> goto exit;
>
> + trans_min = 0;
> if (INTEL_GEN(dev_priv) >= 10)
> trans_min = 4;
BSpec WA section tells not to enable transition watermark for any GEN-9
platforms (that was the assumption with this patch)
But anyway trans_min value for GEN9 is 14 blocks, IMO adding else case
with trans_min = 14; will be logical solution to this.

-Mahesh