From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:58514 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750791AbdALRVd (ORCPT ); Thu, 12 Jan 2017 12:21:33 -0500 Date: Thu, 12 Jan 2017 18:21:36 +0100 From: Greg Kroah-Hartman To: Imre Deak Cc: stable@vger.kernel.org, Ville =?iso-8859-1?Q?Syrj=E4l=E4?= , Chris Wilson , Jani Nikula Subject: Re: [PATCH v8] drm/i915/gen9: Fix PCODE polling during CDCLK change notification Message-ID: <20170112172136.GC13342@kroah.com> References: <1484227358-26883-1-git-send-email-imre.deak@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1484227358-26883-1-git-send-email-imre.deak@intel.com> Sender: stable-owner@vger.kernel.org List-ID: On Thu, Jan 12, 2017 at 03:22:38PM +0200, Imre Deak wrote: > commit 848496e5902833600f7992f4faa82dc1546051ba > Author: Ville Syrj�l� > Date: Wed Jul 13 16:32:03 2016 +0300 > > drm/i915: Wait up to 3ms for the pcu to ack the cdclk change request on SKL > > increased the timeout to match the spec, but we still see a timeout on > at least one SKL. A CDCLK change request following the failed one will > succeed nevertheless. > > I could reproduce this problem easily by running kms_pipe_crc_basic in a > loop. In all failure cases _wait_for() was pre-empted for >3ms and so in > the worst case - when the pre-emption happened right after calculating > timeout__ in _wait_for() - we called skl_cdclk_wait_for_pcu_ready() only > once which failed and so _wait_for() timed out. As opposed to this the > spec says to keep retrying the request for at most a 3ms period. > > To fix this send the first request explicitly to guarantee that there is > 3ms between the first and last request. Though this matches the spec, I > noticed that in rare cases this can still time out if we sent only a few > requests (in the worst case 2) _and_ PCODE is busy for some reason even > after a previous request and a 3ms delay. To work around this retry the > polling with pre-emption disabled to maximize the number of requests. > Also increase the timeout to 10ms to account for interrupts that could > reduce the number of requests. With this change I couldn't trigger > the problem. > > v2: > - Use 1ms poll period instead of 10us. (Chris) > v3: > - Poll with pre-emption disabled to increase the number of request > attempts. (Ville, Chris) > - Factor out a helper to poll, it's also needed by the next patch. > v4: > - Pass reply_mask, reply to skl_pcode_request(), instead of assuming the > reply is generic. (Ville) > v5: > - List the request specific timeout values as code comment. (Ville) > v6: > - Try the poll first with preemption enabled. > - Add code comment about first request being queued by PCODE. (Art) > - Add timeout_base_ms argument. (Ville) > v7: > - Clarify code comment about first queued request. (Chris) > v8: > - Rebased on 4.9.2 > > Cc: Ville Syrj�l� > Cc: Chris Wilson > Cc: Art Runyan > Cc: # v4.2- : 3b2c171 : drm/i915: Wait up to 3ms > Cc: # v4.2- > Fixes: 5d96d8afcfbb ("drm/i915/skl: Deinit/init the display at suspend/resume") > Reference: https://bugs.freedesktop.org/show_bug.cgi?id=97929 > Testcase: igt/kms_pipe_crc_basic/suspend-read-crc-pipe-B > Signed-off-by: Imre Deak > Reviewed-by: Chris Wilson > Link: http://patchwork.freedesktop.org/patch/msgid/1480955258-26311-1-git-send-email-imre.deak@intel.com > (cherry picked from commit a0b8a1fe34430c3a82258e8cb45f5968bdf31afd) > Signed-off-by: Jani Nikula > --- > drivers/gpu/drm/i915/i915_drv.h | 2 + > drivers/gpu/drm/i915/intel_display.c | 31 +++++---------- > drivers/gpu/drm/i915/intel_pm.c | 75 ++++++++++++++++++++++++++++++++++++ > 3 files changed, 87 insertions(+), 21 deletions(-) What tree is this patch for? Please give us a hint, we don't like guessing... thanks, greg k-h