[Intel-gfx] [PATCH] drm/i915: fix handling of the disable_power_well module option

[Patrik Jakobsson]

On Wed, Nov 11, 2015 at 07:03:54PM +0200, Imre Deak wrote:
> When this option is 0 (so the power well support is disabled) we are
> supposed to enable all power wells once and don't disable them unless we
> system suspend the device. Currently if the option is 0, we can call the
> power well enable handlers multiple times, whenever their refcount
> changes from 0->1. This may not be a problem for the HW, but it's not
> logical and may trigger some warnings in the power well code which
> doesn't expect this. So simply keep around a reference while we are
> not system suspended to solve this. For simplicity mark the module
> option read only, so we don't need to deal with re-enabling the feature
> during runtime. If someone really needs that it could be added later in
> a more proper way.
> 
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_params.c      |  2 +-
>  drivers/gpu/drm/i915/intel_runtime_pm.c | 16 +++++++++++++++-
>  2 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
> index 7cf7474..2b36e67 100644
> --- a/drivers/gpu/drm/i915/i915_params.c
> +++ b/drivers/gpu/drm/i915/i915_params.c
> @@ -131,7 +131,7 @@ module_param_named_unsafe(preliminary_hw_support, i915.preliminary_hw_support, i
>  MODULE_PARM_DESC(preliminary_hw_support,
>  	"Enable preliminary hardware support.");
>  
> -module_param_named_unsafe(disable_power_well, i915.disable_power_well, int, 0600);
> +module_param_named_unsafe(disable_power_well, i915.disable_power_well, int, 0400);
>  MODULE_PARM_DESC(disable_power_well,
>  	"Disable display power wells when possible "
>  	"(-1=auto [default], 0=power wells always on, 1=power wells disabled when possible)");
> diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
> index b33969b..d167a45 100644
> --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> @@ -1427,7 +1427,7 @@ void intel_display_power_put(struct drm_i915_private *dev_priv,
>  	for_each_power_well_rev(i, power_well, BIT(domain), power_domains) {
>  		WARN_ON(!power_well->count);
>  
> -		if (!--power_well->count && i915.disable_power_well)
> +		if (!--power_well->count)
>  			intel_power_well_disable(dev_priv, power_well);
>  	}
>  
> @@ -1899,6 +1899,10 @@ void intel_power_domains_fini(struct drm_i915_private *dev_priv)
>  	 * the power well is not enabled, so just enable it in case
>  	 * we're going to unload/reload. */
>  	intel_display_set_init_power(dev_priv, true);
> +
> +	/* Remove the refcount we took to keep power well support disabled. */
> +	if (!i915.disable_power_well)
> +		intel_display_power_put(dev_priv, POWER_DOMAIN_INIT);
>  }
>  
>  static void intel_power_domains_sync_hw(struct drm_i915_private *dev_priv)
> @@ -2099,6 +2103,9 @@ void intel_power_domains_init_hw(struct drm_i915_private *dev_priv, bool resume)
>  
>  	/* For now, we need the power well to be always enabled. */
>  	intel_display_set_init_power(dev_priv, true);
> +	/* Disable power support if the user asked so. */
> +	if (!i915.disable_power_well)
> +		intel_display_power_get(dev_priv, POWER_DOMAIN_INIT);
>  	intel_power_domains_sync_hw(dev_priv);
>  	power_domains->initializing = false;
>  }
> @@ -2114,6 +2121,13 @@ void intel_power_domains_suspend(struct drm_i915_private *dev_priv)
>  {
>  	if (IS_SKYLAKE(dev_priv) || IS_KABYLAKE(dev_priv))
>  		skl_display_core_uninit(dev_priv);
> +
> +	/*
> +	 * Even if power well support was disabled we still want to disabled
> +	 * we want to disable the power wells while we are system suspended.
> +	 */

This comment needs fixing. With that done:

Reviewed-by: Patrik Jakobsson <patrik.jakobsson at linux.intel.com>

> +	if (!i915.disable_power_well)
> +		intel_display_power_put(dev_priv, POWER_DOMAIN_INIT);
>  }
>  
>  /**
> -- 
> 2.5.0
> 
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