Re: [PATCH] drm/i915: perform scaler_id check for skl+

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, May 07, 2015 at 06:16:04PM -0700, Chandra Konduru wrote:
> Scaler id is added for skylake to handle its shared scalers.
> This is not applicable for platforms before SKL. This patch limits
> the scaler_id check during intel_pipe_config_compare to platforms
> SKL and above.

Please add a References: line here with the bug report from mailing lists.
Also please do a quick query of bugzilla, QA should have hit this too and
filed it.

Also please reference the commit that introduce this warning (or the most
likely one).

> Signed-off-by: Chandra Konduru <chandra.konduru@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index c297cdc..fc1b7f9 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -11846,7 +11846,9 @@ intel_pipe_config_compare(struct drm_device *dev,
>  		PIPE_CONF_CHECK_I(pch_pfit.size);
>  	}
>  
> -	PIPE_CONF_CHECK_I(scaler_state.scaler_id);
> +	if (INTEL_INFO(dev)->gen >= 9) {
> +		PIPE_CONF_CHECK_I(scaler_state.scaler_id);
> +	}

In general all the state should be left as 0 on platforms that don't
support it. We only have conditionals for platforms where we compute
state, but for some hw-specific reason can't always reconstruct it from hw
state alone. Hence the correct fix would be to make sure that we leave
scaler_id == 0 in both compute_config and read_hw_state functions for gen
< 9.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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