From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755293Ab2C0TDT (ORCPT ); Tue, 27 Mar 2012 15:03:19 -0400 Received: from smtp.fireflyinternet.com ([109.228.6.236]:62514 "EHLO fireflyinternet.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751003Ab2C0TDS (ORCPT ); Tue, 27 Mar 2012 15:03:18 -0400 X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.66.37; From: Chris Wilson Subject: Re: [PATCH 13/13 v4] drm/i915/intel_i2c: reuse GMBUS2 value read in polling loop To: Daniel Kurtz , Daniel Vetter , Keith Packard , David Airlie , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: Benson Leung , Yufeng Shen , Daniel Kurtz In-Reply-To: <1332873382-29373-14-git-send-email-djkurtz@chromium.org> References: <1332873382-29373-1-git-send-email-djkurtz@chromium.org> <1332873382-29373-14-git-send-email-djkurtz@chromium.org> Date: Tue, 27 Mar 2012 20:02:59 +0100 X-Originating-IP: 78.156.66.37 Message-ID: <1332874994_117123@CP5-2952> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 28 Mar 2012 02:36:22 +0800, Daniel Kurtz wrote: > Save the GMBUS2 value read while polling for state changes, and then > reuse this value when determining for which reason the loops were exited. > This is a small optimization which saves a couple of bus accesses for > memory mapped IO registers. > > To avoid "assigning in if clause" checkpatch errors", use a ret variable > to store the wait_for macro return value. > > Signed-off-by: Daniel Kurtz > --- > drivers/gpu/drm/i915/intel_i2c.c | 32 ++++++++++++++++++++------------ > 1 files changed, 20 insertions(+), 12 deletions(-) > > diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c > index c71f3dc..174fc71 100644 > --- a/drivers/gpu/drm/i915/intel_i2c.c > +++ b/drivers/gpu/drm/i915/intel_i2c.c > @@ -210,6 +210,7 @@ gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg, > int reg_offset = dev_priv->gpio_mmio_base; > u16 len = msg->len; > u8 *buf = msg->buf; > + u32 gmbus2; Does the temporary really need such broad scoping? > I915_WRITE(GMBUS1 + reg_offset, > gmbus1 | > @@ -219,13 +220,15 @@ gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg, > GMBUS_SLAVE_READ | GMBUS_SW_RDY); > POSTING_READ(GMBUS2 + reg_offset); Might as well shave this read as well. > do { > + int ret; > u32 val, loop = 0; > > - if (wait_for(I915_READ(GMBUS2 + reg_offset) & > - (GMBUS_SATOER | GMBUS_HW_RDY), > - 50)) > + ret = wait_for((gmbus2 = I915_READ(GMBUS2 + reg_offset)) & > + (GMBUS_SATOER | GMBUS_HW_RDY), > + 50); > + if (ret) > return -ETIMEDOUT; > - if (I915_READ(GMBUS2 + reg_offset) & GMBUS_SATOER) > + if (gmbus2 & GMBUS_SATOER) > return -ENXIO; > > val = I915_READ(GMBUS3 + reg_offset); > @@ -245,6 +248,7 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg) > u16 len = msg->len; > u8 *buf = msg->buf; > u32 val, loop; > + u32 gmbus2; > > val = loop = 0; > while (len && loop < 4) { > @@ -260,6 +264,7 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg) > GMBUS_SLAVE_WRITE | GMBUS_SW_RDY); > POSTING_READ(GMBUS2 + reg_offset); > while (len) { > + int ret; > val = loop = 0; > do { > val |= *buf++ << (8 * loop); > @@ -268,11 +273,12 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg) > I915_WRITE(GMBUS3 + reg_offset, val); > POSTING_READ(GMBUS2 + reg_offset); And here. -- Chris Wilson, Intel Open Source Technology Centre