Re: [PATCH 2/2] drm/i915/vlv: remove wait for previous GFX clk disable request

From: Deepak S <deepak.s@linux.intel.com>
To: Jesse Barnes <jbarnes@virtuousgeek.org>, intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 2/2] drm/i915/vlv: remove wait for previous GFX clk disable request
Date: Thu, 02 Apr 2015 16:11:56 +0530	[thread overview]
Message-ID: <551D1CF4.5000505@linux.intel.com> (raw)
In-Reply-To: <1427923378-2116-2-git-send-email-jbarnes@virtuousgeek.org>

On Thursday 02 April 2015 02:52 AM, Jesse Barnes wrote:
> Looks like it was introduced in:
>
> commit 650ad970a39f8b6164fe8613edc150f585315289
> Author: Imre Deak <imre.deak@intel.com>
> Date:   Fri Apr 18 16:35:02 2014 +0300
>
>      drm/i915: vlv: factor out vlv_force_gfx_clock and check for pending force-of
>
> but I'm not sure why.  It has caused problems for us in the past (see
> 85250ddff7a603dfe0ec0503a9e6395f79424f61 and
> 8d4eee9cd7a170342dc6fbc2ee19ae77031a8cd5) and doesn't seem to be
> required, so let's just drop it.
>
> References: https://bugs.freedesktop.org/show_bug.cgi?id=89611
> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> ---
>   drivers/gpu/drm/i915/i915_drv.c | 14 --------------
>   1 file changed, 14 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 4d6d6f0..c3fdbb0 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -1208,21 +1208,7 @@ int vlv_force_gfx_clock(struct drm_i915_private *dev_priv, bool force_on)
>   	u32 val;
>   	int err;
>   
> -	val = I915_READ(VLV_GTLC_SURVIVABILITY_REG);
> -
>   #define COND (I915_READ(VLV_GTLC_SURVIVABILITY_REG) & VLV_GFX_CLK_STATUS_BIT)
> -	/* Wait for a previous force-off to settle */
> -	if (force_on && !IS_CHERRYVIEW(dev_priv->dev)) {
> -		/* WARN_ON only for the Valleyview */
> -		WARN_ON(!!(val & VLV_GFX_CLK_FORCE_ON_BIT) == force_on);
> -
> -		err = wait_for(!COND, 20);
> -		if (err) {
> -			DRM_ERROR("timeout waiting for GFX clock force-off (%08x)\n",
> -				  I915_READ(VLV_GTLC_SURVIVABILITY_REG));
> -			return err;
> -		}
> -	}
>   

I agree, I do not think we need to wait for previous Gfx clk force-off.
Also, I do not see any race condition happening between diff Gfx force clk in driver. Lets just drop it :)

Reviewed-by: Deepak S  <deepak.s@linux.intel.com>

>   	val = I915_READ(VLV_GTLC_SURVIVABILITY_REG);
>   	val &= ~VLV_GFX_CLK_FORCE_ON_BIT;

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