From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 59C03C433E3 for ; Fri, 19 Mar 2021 17:29:50 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 178BD6197A for ; Fri, 19 Mar 2021 17:29:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 178BD6197A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id A10226E098; Fri, 19 Mar 2021 17:29:49 +0000 (UTC) Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by gabe.freedesktop.org (Postfix) with ESMTPS id 944F06EA5E for ; Fri, 19 Mar 2021 17:29:48 +0000 (UTC) IronPort-SDR: ftAlX7oE7vhz0OjLt/kDyYzJUW71pxz+7ZqZQN17Y/9vabisLKWeqVlw+HIzcQHhax10WLNCfY CQCxpMdRmTnQ== X-IronPort-AV: E=McAfee;i="6000,8403,9928"; a="209967614" X-IronPort-AV: E=Sophos;i="5.81,262,1610438400"; d="scan'208";a="209967614" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Mar 2021 10:29:47 -0700 IronPort-SDR: Wty3SGUNGDMA6yjUa+Fid+JrPHvHcy1EPG4CcFyZ6LEY3YRs9UqscAsa3BHKOegqegKT6ONgwe 7aA+uGasc7Vw== X-IronPort-AV: E=Sophos;i="5.81,262,1610438400"; d="scan'208";a="413593939" Received: from ideak-desk.fi.intel.com ([10.237.68.141]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Mar 2021 10:29:45 -0700 Date: Fri, 19 Mar 2021 19:29:41 +0200 From: Imre Deak To: Lyude Paul Message-ID: <20210319172941.GI94006@ideak-desk.fi.intel.com> References: <20210317184901.4029798-1-imre.deak@intel.com> <20210317184901.4029798-2-imre.deak@intel.com> <20210318174907.GE4128033@ideak-desk.fi.intel.com> <20210318180645.GG4128033@ideak-desk.fi.intel.com> <20210318231749.GA23036@ideak-desk.fi.intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Subject: Re: [Intel-gfx] [PATCH v2 1/3] drm/i915/ilk-glk: Fix link training on links with LTTPRs X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: imre.deak@intel.com Cc: "mail@bodograumann.de" , "santiago.zarate@suse.com" , "tiwai@suse.de" , "intel-gfx@lists.freedesktop.org" , "stable@vger.kernel.org" Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Fri, Mar 19, 2021 at 01:25:08PM -0400, Lyude Paul wrote: > On Fri, 2021-03-19 at 01:17 +0200, Imre Deak wrote: > > On Fri, Mar 19, 2021 at 12:04:54AM +0200, Almahallawy, Khaled wrote: > > > On Thu, 2021-03-18 at 20:06 +0200, Imre Deak wrote: > > > > On Thu, Mar 18, 2021 at 07:49:13PM +0200, Imre Deak wrote: > > > > > On Thu, Mar 18, 2021 at 07:33:20PM +0200, Ville Syrj=E4l=E4 wrote: > > > > > > On Wed, Mar 17, 2021 at 08:48:59PM +0200, Imre Deak wrote: > > > > > > > The spec requires to use at least 3.2ms for the AUX timeout > > > > > > > period if > > > > > > > there are LT-tunable PHY Repeaters on the link (2.11.2). An > > > > > > > upcoming > > > > > > > spec update makes this more specific, by requiring a 3.2ms > > > > > > > minimum > > > > > > > timeout period for the LTTPR detection reading the 0xF0000- > > > > > > > 0xF0007 > > > > > > > range (3.6.5.1). > > > > > > = > > > > > > I'm pondering if we could reduce the timeout after having > > > > > > determined > > > > > > wherther LTTPRs are present or not? But maybe that wouldn't > > > > > > really speed > > > > > > up anything since we can't reduce the timeout until after > > > > > > detecting > > > > > > *something*. And once there is something there we shouldn't > > > > > > really get > > > > > > any more timeouts I guess. So probably a totally stupid idea. > > > > > = > > > > > Right, if something is connected it would take anyway as much time > > > > > as it > > > > > takes for the sink to reply whether or not we decreased the > > > > > timeout. > > > > > = > > > > > However if nothing is connected, we have the excessive timeout > > > > > Khaled > > > > > already noticed (160 * 4ms =3D 6.4 sec on ICL+). I think to impro= ve > > > > > that > > > > > we could scale the total number of retries by making it > > > > > total_timeout/platform_specific_timeout (letting total_timeout=3D= 2sec > > > > > for > > > > > instance) or just changing the drm retry logic to be time based > > > > > instead > > > > > of the number of retries we use atm. > > > > = > > > > Doh, reducing simply the HW timeouts would be enough to fix this. > > > = > > > What about Lyude's suggestion ( > > > https://patchwork.freedesktop.org/patch/420369/#comment_756572) > > > to drop the retries in intel_dp_aux_xfer() > > > /* Must try at least 3 times according to DP spec */ > > > for (try =3D 0; try < 5; try++) { > > > = > > > And use only the retries in drm_dpcd_access? > > = > > I think it would work if we can make the retries configurable and set it > > to > > =A0=A0=A0=A0=A0=A0=A0=A0retries =3D total_timeout / platform_specific_t= imeout_per_retry > > = > > where total_timeout would be something reasonable like 1 sec. > = > I actually think I'm more open to the idea of configurable retries after > learning that apparently this is a thing that the i2c subsystem does - so > there's more precedence for it in the rest of the kernel than I originally > thought. > = > I'm still curious if we need these extra retries in here though - there s= eems to > be one set of retries that is actually platform specific, and then just a= random > set of 5 retries that don't seem to have anything to do with platform spe= cific > behavior - so I think it'd still be worth giving a shot at getting rid of= that The platform specific part of the timeout is the one desctibed in the maximum timeout values comments. > > > Thanks > > > Khaled > > > = > > > > = > > > > > > Anyways, this seems about the only thing we can do given the > > > > > > limited > > > > > > hw capabilities. > > > > > > Reviewed-by: Ville Syrj=E4l=E4 > > > > > > = > > > > > > > Accordingly disable LTTPR detection until GLK, where the > > > > > > > maximum timeout > > > > > > > we can set is only 1.6ms. > > > > > > > = > > > > > > > Link training in the non-transparent mode is known to fail at > > > > > > > least on > > > > > > > some SKL systems with a WD19 dock on the link, which exposes = an > > > > > > > LTTPR > > > > > > > (see the References below). While this could have different > > > > > > > reasons > > > > > > > besides the too short AUX timeout used, not detecting LTTPRs > > > > > > > (and so not > > > > > > > using the non-transparent LT mode) fixes link training on the= se > > > > > > > systems. > > > > > > > = > > > > > > > While at it add a code comment about the platform specific > > > > > > > maximum > > > > > > > timeout values. > > > > > > > = > > > > > > > v2: Add a comment about the g4x maximum timeout as well. > > > > > > > (Ville) > > > > > > > = > > > > > > > Reported-by: Takashi Iwai > > > > > > > Reported-and-tested-by: Santiago Zarate < > > > > > > > santiago.zarate@suse.com> > > > > > > > Reported-and-tested-by: Bodo Graumann > > > > > > > References: > > > > > > > https://gitlab.freedesktop.org/drm/intel/-/issues/3166 > > > > > > > Fixes: b30edfd8d0b4 ("drm/i915: Switch to LTTPR non-transpare= nt > > > > > > > mode link training") > > > > > > > Cc: # v5.11 > > > > > > > Cc: Takashi Iwai > > > > > > > Cc: Ville Syrj=E4l=E4 > > > > > > > Signed-off-by: Imre Deak > > > > > > > --- > > > > > > > =A0drivers/gpu/drm/i915/display/intel_dp_aux.c=A0=A0=A0=A0=A0= =A0 |=A0 7 +++++++ > > > > > > > =A0.../gpu/drm/i915/display/intel_dp_link_training.c | 15 > > > > > > > ++++++++++++--- > > > > > > > =A02 files changed, 19 insertions(+), 3 deletions(-) > > > > > > > = > > > > > > > diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c > > > > > > > b/drivers/gpu/drm/i915/display/intel_dp_aux.c > > > > > > > index eaebf123310a..10fe17b7280d 100644 > > > > > > > --- a/drivers/gpu/drm/i915/display/intel_dp_aux.c > > > > > > > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c > > > > > > > @@ -133,6 +133,7 @@ static u32 g4x_get_aux_send_ctl(struct > > > > > > > intel_dp *intel_dp, > > > > > > > =A0else > > > > > > > =A0precharge =3D 5; > > > > > > > = > > > > > > > +/* Max timeout value on G4x-BDW: 1.6ms */ > > > > > > > =A0if (IS_BROADWELL(dev_priv)) > > > > > > > =A0timeout =3D DP_AUX_CH_CTL_TIME_OUT_600us; > > > > > > > =A0else > > > > > > > @@ -159,6 +160,12 @@ static u32 skl_get_aux_send_ctl(struct > > > > > > > intel_dp *intel_dp, > > > > > > > =A0enum phy phy =3D intel_port_to_phy(i915, dig_port- > > > > > > > > base.port); > > > > > > > =A0u32 ret; > > > > > > > = > > > > > > > +/* > > > > > > > + * Max timeout values: > > > > > > > + * SKL-GLK: 1.6ms > > > > > > > + * CNL: 3.2ms > > > > > > > + * ICL+: 4ms > > > > > > > + */ > > > > > > > =A0ret =3D DP_AUX_CH_CTL_SEND_BUSY | > > > > > > > =A0=A0=A0=A0=A0=A0 DP_AUX_CH_CTL_DONE | > > > > > > > =A0=A0=A0=A0=A0=A0 DP_AUX_CH_CTL_INTERRUPT | > > > > > > > diff --git > > > > > > > a/drivers/gpu/drm/i915/display/intel_dp_link_training.c > > > > > > > b/drivers/gpu/drm/i915/display/intel_dp_link_training.c > > > > > > > index 19ba7c7cbaab..c0e25c75c105 100644 > > > > > > > --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c > > > > > > > +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c > > > > > > > @@ -82,6 +82,18 @@ static void > > > > > > > intel_dp_read_lttpr_phy_caps(struct intel_dp *intel_dp, > > > > > > > = > > > > > > > =A0static bool intel_dp_read_lttpr_common_caps(struct intel_dp > > > > > > > *intel_dp) > > > > > > > =A0{ > > > > > > > +struct drm_i915_private *i915 =3D dp_to_i915(intel_dp); > > > > > > > + > > > > > > > +if (intel_dp_is_edp(intel_dp)) > > > > > > > +return false; > > > > > > > + > > > > > > > +/* > > > > > > > + * Detecting LTTPRs must be avoided on platforms with > > > > > > > an AUX timeout > > > > > > > + * period < 3.2ms. (see DP Standard v2.0, 2.11.2, > > > > > > > 3.6.6.1). > > > > > > > + */ > > > > > > > +if (INTEL_GEN(i915) < 10) > > > > > > > +return false; > > > > > > > + > > > > > > > =A0if (drm_dp_read_lttpr_common_caps(&intel_dp->aux, > > > > > > > =A0=A0 intel_dp- > > > > > > > > lttpr_common_caps) < 0) { > > > > > > > =A0memset(intel_dp->lttpr_common_caps, 0, > > > > > > > @@ -127,9 +139,6 @@ int intel_dp_lttpr_init(struct intel_dp > > > > > > > *intel_dp) > > > > > > > =A0bool ret; > > > > > > > =A0int i; > > > > > > > = > > > > > > > -if (intel_dp_is_edp(intel_dp)) > > > > > > > -return 0; > > > > > > > - > > > > > > > =A0ret =3D intel_dp_read_lttpr_common_caps(intel_dp); > > > > > > > =A0if (!ret) > > > > > > > =A0return 0; > > > > > > > -- > > > > > > > 2.25.1 > > > > > > = > > > > > > -- > > > > > > Ville Syrj=E4l=E4 > > > > > > Intel > > = > = > -- = > Sincerely, > Lyude Paul (she/her) > Software Engineer at Red Hat > = > Note: I deal with a lot of emails and have a lot of bugs on my plate. If = you've > asked me a question, are waiting for a review/merge on a patch, etc. and I > haven't responded in a while, please feel free to send me another email t= o check > on my status. I don't bite! > = _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx