From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Widawsky Subject: Re: [PATCH 23/30] drm/i915: Cache GT fifo count for SandyBridge Date: Wed, 13 Apr 2011 19:21:30 -0700 Message-ID: <20110414022130.GA5189@lundgren.kumite> References: <1302640318-23165-1-git-send-email-chris@chris-wilson.co.uk> <1302640318-23165-24-git-send-email-chris@chris-wilson.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from cloud01.chad-versace.us (184-106-247-128.static.cloud-ips.com [184.106.247.128]) by gabe.freedesktop.org (Postfix) with ESMTP id 661139E837 for ; Wed, 13 Apr 2011 19:21:35 -0700 (PDT) Content-Disposition: inline In-Reply-To: <1302640318-23165-24-git-send-email-chris@chris-wilson.co.uk> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org To: Chris Wilson Cc: intel-gfx@lists.freedesktop.org List-Id: intel-gfx@lists.freedesktop.org On Tue, Apr 12, 2011 at 09:31:51PM +0100, Chris Wilson wrote: > The read back of the available FIFO entries is vital for system > stability, but extremely costly. However, we only need a guide so as to > avoid eating into the reserved entries and since we are the only > consumer we can cache the read of the count from the last write. > > Signed-off-by: Chris Wilson > --- > drivers/gpu/drm/i915/i915_drv.c | 14 +++++++++----- > drivers/gpu/drm/i915/i915_drv.h | 1 + > 2 files changed, 10 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c > index c416c1d..1146abd 100644 > --- a/drivers/gpu/drm/i915/i915_drv.c > +++ b/drivers/gpu/drm/i915/i915_drv.c > @@ -287,12 +287,16 @@ void __gen6_gt_force_wake_put(struct drm_i915_private *dev_priv) > > void __gen6_gt_wait_for_fifo(struct drm_i915_private *dev_priv) > { > - int loop = 500; > - u32 fifo = I915_READ_NOTRACE(GT_FIFO_FREE_ENTRIES); > - while (fifo < 20 && loop--) { > - udelay(10); > - fifo = I915_READ_NOTRACE(GT_FIFO_FREE_ENTRIES); > + if (dev_priv->gt_fifo_count < 20 ) { > + int loop = 500; > + u32 fifo = I915_READ_NOTRACE(GT_FIFO_FREE_ENTRIES); > + while (fifo < 20 && loop--) { > + udelay(10); > + fifo = I915_READ_NOTRACE(GT_FIFO_FREE_ENTRIES); > + } > + dev_priv->gt_fifo_count = fifo; > } > + dev_priv->gt_fifo_count--; > } > > static int i915_drm_freeze(struct drm_device *dev) > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h > index 2f45228..c837e10 100644 > --- a/drivers/gpu/drm/i915/i915_drv.h > +++ b/drivers/gpu/drm/i915/i915_drv.h > @@ -268,6 +268,7 @@ typedef struct drm_i915_private { > int relative_constants_mode; > > void __iomem *regs; > + u32 gt_fifo_count; > > struct intel_gmbus { > struct i2c_adapter adapter; I'm sure you noticed that we have seriously problem both here and in the put()/get() if the condition doesn't clear up in loop number of times. I'd probably add a WARN(!loop, "uh oh"), but the patch is better than what is there currently, so I'm okay either way. Reviewed-by: Ben Widawsky