Re: [PATCH 2/2] drm/i915: kill cargo-culted locking from power well code

[Rodrigo Vivi <rodrigo.vivi@gmail.com>]

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>

On Wed, Jan 30, 2013 at 12:59 PM, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> We may not concurrently change the power wells code. Which
> is already guaranteed since modesets aren't concurrent. That
> leaves races against setup/teardown/suspend/resume, and for
> those we already (try) rather hard not to hit concurrent
> modesets.
>
> No debug WARN_ON added since that would require us to grab the
> modeset locks in init/suspend code. Which is again just cargo
> culting since just grabbing the locks in those paths isn't good
> enough, we need the right order of operations, too.
>
> Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  drivers/gpu/drm/i915/intel_pm.c |    4 ----
>  1 file changed, 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 703219c..f024e7d 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -4091,8 +4091,6 @@ void intel_init_power_well(struct drm_device *dev)
>         if (!IS_HASWELL(dev))
>                 return;
>
> -       mutex_lock(&dev->struct_mutex);
> -
>         /* For now, we need the power well to be always enabled. */
>         intel_set_power_well(dev, true);
>
> @@ -4100,8 +4098,6 @@ void intel_init_power_well(struct drm_device *dev)
>          * the driver is in charge now. */
>         if (I915_READ(HSW_PWR_WELL_BIOS) & HSW_PWR_WELL_ENABLE)
>                 I915_WRITE(HSW_PWR_WELL_BIOS, 0);
> -
> -       mutex_unlock(&dev->struct_mutex);
>  }
>
>  /* Set up chip specific power management-related functions */
> --
> 1.7.10.4
>
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-- 
Rodrigo Vivi
Blog: http://blog.vivi.eng.br