On Tue, Jun 25, 2019 at 10:54:11AM -0700, Lucas De Marchi wrote:
> This prepares to have possibly more than 3 pipes. I didn't want to
> continue the previous approach since the check for "are the disabled
> pipes the last ones" poses a combinatory explosion. We need that check
> because in several places of the code we have that assumption. If that
> ever becomes false in a new HW, other parts of the code would have to
> change.
> 
> Now we start by considering we have info->num_pipes enabled and disable
> each pipe that is marked as disabled. Then it's a simple matter of
> checking if we have at least one pipe and that all the enabled ones are
> the first pipes, i.e. there are no holes in the bitmask.
> 
> Cc: Jose Souza <[email protected]>
> Cc: Ville Syrjälä <[email protected]>
> Signed-off-by: Lucas De Marchi <[email protected]>

Looks good.

Reviewed-by: Ville Syrjälä <[email protected]>

> ---
>  drivers/gpu/drm/i915/intel_device_info.c | 36 +++++++++---------------
>  1 file changed, 13 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_device_info.c 
> b/drivers/gpu/drm/i915/intel_device_info.c
> index 7135d8dc32a7..e64536e1fd1b 100644
> --- a/drivers/gpu/drm/i915/intel_device_info.c
> +++ b/drivers/gpu/drm/i915/intel_device_info.c
> @@ -929,35 +929,25 @@ void intel_device_info_runtime_init(struct 
> drm_i915_private *dev_priv)
>               }
>       } else if (HAS_DISPLAY(dev_priv) && INTEL_GEN(dev_priv) >= 9) {
>               u32 dfsm = I915_READ(SKL_DFSM);
> -             u8 disabled_mask = 0;
> -             bool invalid;
> -             int num_bits;
> +             u8 enabled_mask = BIT(info->num_pipes) - 1;
>  
>               if (dfsm & SKL_DFSM_PIPE_A_DISABLE)
> -                     disabled_mask |= BIT(PIPE_A);
> +                     enabled_mask &= ~BIT(PIPE_A);
>               if (dfsm & SKL_DFSM_PIPE_B_DISABLE)
> -                     disabled_mask |= BIT(PIPE_B);
> +                     enabled_mask &= ~BIT(PIPE_B);
>               if (dfsm & SKL_DFSM_PIPE_C_DISABLE)
> -                     disabled_mask |= BIT(PIPE_C);
> -
> -             num_bits = hweight8(disabled_mask);
> -
> -             switch (disabled_mask) {
> -             case BIT(PIPE_A):
> -             case BIT(PIPE_B):
> -             case BIT(PIPE_A) | BIT(PIPE_B):
> -             case BIT(PIPE_A) | BIT(PIPE_C):
> -                     invalid = true;
> -                     break;
> -             default:
> -                     invalid = false;
> -             }
> +                     enabled_mask &= ~BIT(PIPE_C);
>  
> -             if (num_bits > info->num_pipes || invalid)
> -                     DRM_ERROR("invalid pipe fuse configuration: 0x%x\n",
> -                               disabled_mask);
> +             /*
> +              * At least one pipe should be enabled and if there are
> +              * disabled pipes, they should be the last ones, with no holes
> +              * in the mask.
> +              */
> +             if (enabled_mask == 0 || !is_power_of_2(enabled_mask + 1))
> +                     DRM_ERROR("invalid pipe fuse configuration: 
> enabled_mask=0x%x\n",
> +                               enabled_mask);
>               else
> -                     info->num_pipes -= num_bits;
> +                     info->num_pipes = hweight8(enabled_mask);
>       }
>  
>       /* Initialize slice/subslice/EU info */
> -- 
> 2.21.0
> 
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-- 
Ville Syrjälä
Intel
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