[Intel-gfx] [PATCH 2/2] drm/i915/vlv: remove wait for previous GFX clk disable request
Imre Deak
imre.deak at intel.com
Thu Apr 2 01:15:53 PDT 2015
On Wed, 2015-04-01 at 14:22 -0700, Jesse Barnes wrote:
> Looks like it was introduced in:
>
> commit 650ad970a39f8b6164fe8613edc150f585315289
> Author: Imre Deak <imre.deak at 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 at 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;
> - }
> - }
The reason I added this is that it's not clear what happens if you try
to force the clock on while the previous force-off operation is still
pending. That is if Punit will correctly cancel turning off the clock in
this case. Since the docs don't clarify this either I thought the above
is safer. Is it the WARN that triggers and only during resume (we also
call the function from vlv_set_rps_idle)? If so, then it's not a real
timeout but BIOS has left the force-on flag set and we could just skip
calling vlv_force_gfx_clock(true) in that case.
If the HW people can confirm that the above isn't needed then I'm also
ok to remove it.
>
> val = I915_READ(VLV_GTLC_SURVIVABILITY_REG);
> val &= ~VLV_GFX_CLK_FORCE_ON_BIT;
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