Re: [PATCH] drm/i915: Use wait_for() to wait for Punit to change GPU freq on VLV

Jesse Barnes
2013-06-26T16:26:28Z

On Wed, 26 Jun 2013 17:43:24 +0300
ville.syrjala@linux.intel.com wrote:

> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Use wait_for() instead of the open coded loop to avoid spreading the
> same old timeout related bugs.
>
> This changes the loop to use msleep(1) instead of udelay(10) when the
> Punit had not yet completed the frequency change. In practice that
> doesn't seem to hurt performance as the Punit appears to be ready pretty
> much always.
>
> Also give the status bit a name, instead of using the magic number 1.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
> drivers/gpu/drm/i915/i915_reg.h | 1 +
> drivers/gpu/drm/i915/intel_pm.c | 11 ++---------
> 2 files changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 10ac3d5..d5199a3 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -363,6 +363,7 @@
> #define PUNIT_REG_GPU_LFM 0xd3
> #define PUNIT_REG_GPU_FREQ_REQ 0xd4
> #define PUNIT_REG_GPU_FREQ_STS 0xd8
> +#define GENFREQSTATUS (1<<0)
> #define PUNIT_REG_MEDIA_TURBO_FREQ_REQ 0xdc
>
> #define PUNIT_FUSE_BUS2 0xf6 /* bits 47:40 */
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index aa48fc6..bff5709 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3074,19 +3074,12 @@ void gen6_set_rps(struct drm_device *dev, u8 val)
> */
> static void vlv_update_rps_cur_delay(struct drm_i915_private *dev_priv)
> {
> - unsigned long timeout = jiffies + msecs_to_jiffies(10);
> u32 pval;
>
> WARN_ON(!mutex_is_locked(&dev_priv->rps.hw_lock));
>
> - do {
> - pval = vlv_punit_read(dev_priv, PUNIT_REG_GPU_FREQ_STS);
> - if (time_after(jiffies, timeout)) {
> - DRM_DEBUG_DRIVER("timed out waiting for Punit\n");
> - break;
> - }
> - udelay(10);
> - } while (pval & 1);
> + if (wait_for(((pval = vlv_punit_read(dev_priv, PUNIT_REG_GPU_FREQ_STS)) & GENFREQSTATUS) == 0, 10))
> + DRM_DEBUG_DRIVER("timed out waiting for Punit\n");
>
> pval >>= 8;
>

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>

--
Jesse Barnes, Intel Open Source Technology Center