[Intel-gfx] [PATCH 3/4] drm/i915/gen9: Fix clearing of the BIOS power well request register

[Ander Conselvan De Oliveira]

On Wed, 2017-02-15 at 13:59 +0200, Imre Deak wrote:
> Atm, in the power well sync_hw hook we are clearing all BIOS request
> bits, not just the one corresponding to the given power well. This could
> turn off an unrelated power well inadvertently if it didn't have a
> request bit set in the driver request register.
> 
> This didn't cause a problem so far, since we enabled all power wells
> explicitly before clearing the BIOS request register. A follow-up
> patchset will add power wells that won't get enabled this way, so fix up
> the inconsistency.
> 
> Cc: Ander Conselvan de Oliveira <conselvan2 at gmail.com>
> Cc: David Weinehall <david.weinehall at linux.intel.com>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_runtime_pm.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
> index f9aff26..b7b0e0f 100644
> --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> @@ -887,8 +887,13 @@ static bool skl_power_well_enabled(struct drm_i915_private *dev_priv,
>  static void skl_power_well_sync_hw(struct drm_i915_private *dev_priv,
>  				struct i915_power_well *power_well)
>  {
> +	uint32_t mask = SKL_POWER_WELL_REQ(power_well->id);
> +	uint32_t bios_req = I915_READ(HSW_PWR_WELL_BIOS);
> +
>  	/* Clear any request made by BIOS as driver is taking over */
> -	I915_WRITE(HSW_PWR_WELL_BIOS, 0);
> +	if (bios_req & mask) {
> +		I915_WRITE(HSW_PWR_WELL_BIOS, bios_req & ~mask);
> +	}
>  }
>  
>  static void skl_power_well_enable(struct drm_i915_private *dev_priv,

With this change we still end up disabling every power well from the BIOS
register because of intel_power_domains_sync_hw() iterating over all the power
wells. Maybe that's worth mentioning in the commit message? Dunno.

Anyway,

Reviewed-by: Ander Conselvan de Oliveira <conselvan2 at gmail.com>