[Intel-gfx] [PATCH] drm/i915: Grab power domain in skl_pipe_wm_get_hw_state()

[Pandiyan, Dhinakaran]

On Tue, 2017-12-19 at 13:16 +0100, Maarten Lankhorst wrote:
> This should get rid of unclaimed register debug warnings, if
> it still happens we should put this in a intel_crtc->active check..
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104172


The bugzilla indicates this is a regression from 
"drm/i915: Restore GT performance in headless mode with DMC loaded",
which seems a bit odd to me. That patch should not have disabled a power
well which was enabled before. If anything, it should fix unclaimed
register accesses. 



> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index ab6f1b770891..52d157c00535 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -5477,6 +5477,11 @@ void skl_pipe_wm_get_hw_state(struct drm_crtc *crtc,
>  	int level, max_level;
>  	enum plane_id plane_id;
>  	uint32_t val;
> +	enum intel_display_power_domain power_domain;
> +
> +	power_domain = POWER_DOMAIN_PIPE(pipe);
> +	if (!intel_display_power_get_if_enabled(dev_priv, power_domain))
> +		return;
>  
>  	max_level = ilk_wm_max_level(dev_priv);
>  
> @@ -5500,10 +5505,9 @@ void skl_pipe_wm_get_hw_state(struct drm_crtc *crtc,
>  		skl_wm_level_from_reg_val(val, &wm->trans_wm);
>  	}
>  
> -	if (!intel_crtc->active)
> -		return;
> -

Doing a power_domain_get_if_enabled() before reading the register seems
like the right thing to do, but is power_get_if_enabled() expected to be
correct at this point? The reason I ask is,
modeset_get_crtc_power_domains() is called after skl_wm_get_hw_state().
So, doesn't that mean the pipe power domain might not have been acquired
even if the CRTC is active.



>  	out->linetime = I915_READ(PIPE_WM_LINETIME(pipe));
> +
> +	intel_display_power_put(dev_priv, power_domain);
>  }
>  
>  void skl_wm_get_hw_state(struct drm_device *dev)