From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [PATCH 2/4] drm/i915/dp: increase i2c-over-aux retry interval on AUX DEFER Date: Fri, 20 Sep 2013 23:53:34 +0200 Message-ID: <20130920215334.GP32145@phenom.ffwll.local> References: <523CB674.90006@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ea0-f172.google.com (mail-ea0-f172.google.com [209.85.215.172]) by gabe.freedesktop.org (Postfix) with ESMTP id 41D2BE665F for ; Fri, 20 Sep 2013 14:53:20 -0700 (PDT) Received: by mail-ea0-f172.google.com with SMTP id r16so536213ead.3 for ; Fri, 20 Sep 2013 14:53:19 -0700 (PDT) Content-Disposition: inline In-Reply-To: <523CB674.90006@gmail.com> 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: Todd Previte Cc: intel-gfx@lists.freedesktop.org List-Id: intel-gfx@lists.freedesktop.org On Fri, Sep 20, 2013 at 01:56:20PM -0700, Todd Previte wrote: > On 09/20/2013 06:42 AM, Jani Nikula wrote: > >There is no clear cut rules or specs for the retry interval, as there > >are many factors that affect overall response time. Increase the > >interval, and even more so on branch devices which may have limited i2c > >bit rates. > > > >Signed-off-by: Jani Nikula > >--- > > drivers/gpu/drm/i915/intel_dp.c | 13 ++++++++++++- > > 1 file changed, 12 insertions(+), 1 deletion(-) > > > >diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c > >index 6626514..3afbea9 100644 > >--- a/drivers/gpu/drm/i915/intel_dp.c > >+++ b/drivers/gpu/drm/i915/intel_dp.c > >@@ -678,7 +678,18 @@ intel_dp_i2c_aux_ch(struct i2c_adapter *adapter, int mode, > > DRM_DEBUG_KMS("aux_ch native nack\n"); > > return -EREMOTEIO; > > case AUX_NATIVE_REPLY_DEFER: > >- udelay(100); > >+ /* > >+ * For now, just give more slack to branch devices. We > >+ * could check the DPCD for I2C bit rate capabilities, > >+ * and if available, adjust the interval. We could also > >+ * be more careful with DP-to-Legacy adapters where a > >+ * long legacy cable may force very low I2C bit rates. > >+ */ > >+ if (intel_dp->dpcd[DP_DOWNSTREAMPORT_PRESENT] & > >+ DP_DWN_STRM_PORT_PRESENT) > >+ usleep_range(500, 600); > >+ else > >+ usleep_range(300, 400); > > continue; > > default: > > DRM_ERROR("aux_ch invalid native reply 0x%02x\n", > > Those look like reasonable values to me. > > [Reviewed-by]: Todd Previte > Your mailer sends out html+plaintext multipart mails and in the plaintext section your r-b tags look rather funny. Can you please fix that? Thanks, Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch