Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754707AbcCRR7o (ORCPT ); Fri, 18 Mar 2016 13:59:44 -0400 Received: from mail-wm0-f66.google.com ([74.125.82.66]:33600 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750770AbcCRR7l (ORCPT ); Fri, 18 Mar 2016 13:59:41 -0400 Date: Fri, 18 Mar 2016 19:00:29 +0100 From: Daniel Vetter To: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= Cc: Lyude , Daniel Vetter , intel-gfx@lists.freedesktop.org, arthur.j.runyan@intel.com, open list , dri-devel@lists.freedesktop.org Subject: Re: [Intel-gfx] [PATCH 2/2] drm/i915: Get rid of intel_dp_dpcd_read_wake() Message-ID: <20160318180029.GL14170@phenom.ffwll.local> Mail-Followup-To: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= , Lyude , Daniel Vetter , intel-gfx@lists.freedesktop.org, arthur.j.runyan@intel.com, open list , dri-devel@lists.freedesktop.org References: <1458229245-8634-1-git-send-email-cpaul@redhat.com> <1458229245-8634-2-git-send-email-cpaul@redhat.com> <20160318141345.GG4329@intel.com> <20160318161235.GN4329@intel.com> <20160318164140.GO4329@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20160318164140.GO4329@intel.com> X-Operating-System: Linux phenom 4.3.0-1-amd64 User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3066 Lines: 72 On Fri, Mar 18, 2016 at 06:41:40PM +0200, Ville Syrj?l? wrote: > On Fri, Mar 18, 2016 at 06:12:35PM +0200, Ville Syrj?l? wrote: > > On Fri, Mar 18, 2016 at 04:13:45PM +0200, Ville Syrj?l? wrote: > > > On Thu, Mar 17, 2016 at 11:40:45AM -0400, Lyude wrote: > > > > Since we've fixed up drm_dp_dpcd_read() to allow for retries when things > > > > timeout, there's no use for having this function anymore. Good riddens. > > > > > > > > Signed-off-by: Lyude > > > > --- > > > > drivers/gpu/drm/i915/intel_dp.c | 79 ++++++++++++----------------------------- > > > > 1 file changed, 22 insertions(+), 57 deletions(-) > > > > > > > > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c > > > > index cdc2c15..fb4cbbe5 100644 > > > > --- a/drivers/gpu/drm/i915/intel_dp.c > > > > +++ b/drivers/gpu/drm/i915/intel_dp.c > > > > @@ -3190,47 +3190,14 @@ static void chv_dp_post_pll_disable(struct intel_encoder *encoder) > > > > } > > > > > > > > /* > > > > - * Native read with retry for link status and receiver capability reads for > > > > - * cases where the sink may still be asleep. > > > > - * > > > > - * Sinks are *supposed* to come up within 1ms from an off state, but we're also > > > > - * supposed to retry 3 times per the spec. > > > > - */ > > > > -static ssize_t > > > > -intel_dp_dpcd_read_wake(struct drm_dp_aux *aux, unsigned int offset, > > > > - void *buffer, size_t size) > > > > -{ > > > > - ssize_t ret; > > > > - int i; > > > > - > > > > - /* > > > > - * Sometime we just get the same incorrect byte repeated > > > > - * over the entire buffer. Doing just one throw away read > > > > - * initially seems to "solve" it. > > > > - */ > > > > - drm_dp_dpcd_read(aux, DP_DPCD_REV, buffer, 1); > > > > > > NAK > > > > > > If people keep intentionally breaking my shit I'm going to become > > > really grumpy soon. > > > > Oh, and just in case someone wants to come up with a better kludge, > > I just spent a few minutes analyzing the behavior of this crappy > > monitor a. > > > > What happens is that when the monitor is fully powered up (LED is blue) > > things are fine. After the monitor goes to sleep (LED turns orange) > > the first DPCD read will produce garbage. Further DPCD reads are fine, > > even if I wait a significant amount of time between the reads, as long > > as the monitor didn't do a power on->off cycle in between. So it looks > > like it's always just the first read after power down that gets > > corrupted. > > > > Now I think I'll go and test how writes behave, assuming I can find a > > decently sized chunk of DPCD address space I can write. And maybe I > > should also try i2c-over-aux... > > The first DPCD write after powerdown also got corrupted. But i2c-over-aux > seems unaffected for whatever reason. Do you have an amd card nearby to test there? Would be interesting to confirm that this is indeed a sink bug, and hence that it really all should be in the shared code. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch