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,URIBL_BLOCKED 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 EF31AC433C1 for ; Sat, 20 Mar 2021 07:15:46 +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 7230561967 for ; Sat, 20 Mar 2021 07:15:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7230561967 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 D88326EB39; Sat, 20 Mar 2021 07:15:45 +0000 (UTC) Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by gabe.freedesktop.org (Postfix) with ESMTPS id A0BC96EB39 for ; Sat, 20 Mar 2021 07:15:44 +0000 (UTC) IronPort-SDR: Q276XXDv2TvpgElNsjCH09eYcDhPfs0+52bfR9LdQNEZhxXpqCd0LvgRDxM/BrYab5bgyfCWb8 sOdI8XSlPtQg== X-IronPort-AV: E=McAfee;i="6000,8403,9928"; a="275090492" X-IronPort-AV: E=Sophos;i="5.81,264,1610438400"; d="scan'208";a="275090492" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Mar 2021 00:15:43 -0700 IronPort-SDR: sZ+mIUm+mfb5wW4v3ETusRMfN9ANQPBh08f57tjl0SpyqcCNk/SfCJ+deVSB7IXSTCh22QcWgx IFDGJdvHGUCw== X-IronPort-AV: E=Sophos;i="5.81,264,1610438400"; d="scan'208";a="512726529" Received: from ideak-desk.fi.intel.com ([10.237.68.141]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Mar 2021 00:15:41 -0700 Date: Sat, 20 Mar 2021 09:15:38 +0200 From: Imre Deak To: Lyude Paul Message-ID: <20210320071538.GA361797@ideak-desk.fi.intel.com> References: <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> <20210319172941.GI94006@ideak-desk.fi.intel.com> <20210319210715.GP94006@ideak-desk.fi.intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210319210715.GP94006@ideak-desk.fi.intel.com> 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 11:07:21PM +0200, Imre Deak wrote: > On Fri, Mar 19, 2021 at 04:44:26PM -0400, Lyude Paul wrote: > > > > > [...] > > > > > 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_spec= ific_timeout_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 doe= s - so > > > > there's more precedence for it in the rest of the kernel than I ori= ginally > > > > thought. > > > > = > > > > I'm still curious if we need these extra retries in here though - t= here seems > > > > 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 platfo= rm specific > > > > 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. > > = > > You mean the > > = > > /* Must try at least 3 times according to DP spec */ > > for (try =3D 0; try < 5; try++) { > > = > > bit? I thought that wasn't related to platform specific retries at all,= since > > the code in that loop seems to only reference parts of the DP spec, and= that the > > = > > while ((aux_clock_divider =3D intel_dp->get_aux_clock_divider(intel_dp= , clock++))) { > > = > > Loop was the portion that was platform specific, since it prompts the d= river to > > retry the transaction with different aux clock divider rates depending = on the > > platform in use. Feel free to correct me if I'm wrong though. > = > Nope. I meant every HW transaction will have a platform specific > timeout. For instance it's 1.6ms on SKL, but 4ms on ICL. So now since > the overall retry count is 32 * 5 =3D 160, on SKL we'll retry for ~2.6 > seconds, on ICL we'll retry for ~6.4 seconds (disregarding now the extra > 400usec delay inserted by drm_dp_dpcd_access(), which adds a fixed > ~1.3ms delay). Err, looks like I missed some coffee. Max total timeouts atm, which we would need to make the same on all platforms: g4x-glk: 5 * 32 * 1.6ms + 32 * 400us =3D 268.8ms cnl : 5 * 32 * 3.2ms + 32 * 400us =3D 524.8ms icl+ : 5 * 32 * 4ms + 32 * 400us =3D 652.8ms > This is what I think should be normalized, so that we have the same > amount of overall maximum timeout period on all platforms. > = > > Also - with the timeouts we're seeing, does the LTTPR return NAKs at al= l? That's > > still another thing I had suggested alternate workarounds for so that w= e could > > terminate transactions immediately on NAKs, so I wonder if that could s= ave time > > here as well. > = > There's not much LTTPR specific in that wrt. what sinks would do > normally (no NAKs for read, only for writes) except LTTPRs may rewrite > NAKs to ACKs to account for buggy monitors returning NAKs when reading > the 0xf0000 -> range. But I'd suggest not dealing with this aspect now, > just sanitize the above retry thing, as you suggested, remove the i915 > retry loop and make the drm retry loop configurable. > = > (In any case I also had the idea to stop transactions early when HPD > gets deasserted, but not sure if that's completely robust.) > = > > > > > > 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 f= ail at > > > > > > > > > > least on > > > > > > > > > > some SKL systems with a WD19 dock on the link, which ex= poses an > > > > > > > > > > LTTPR > > > > > > > > > > (see the References below). While this could have diffe= rent > > > > > > > > > > reasons > > > > > > > > > > besides the too short AUX timeout used, not detecting L= TTPRs > > > > > > > > > > (and so not > > > > > > > > > > using the non-transparent LT mode) fixes link training = on these > > > > > > > > > > systems. > > > > > > > > > > = > > > > > > > > > > While at it add a code comment about the platform speci= fic > > > > > > > > > > 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-tra= nsparent > > > > > > > > > > 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(str= uct > > > > > > > > > > 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(st= ruct > > > > > > > > > > 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_traini= ng.c > > > > > > > > > > +++ b/drivers/gpu/drm/i915/display/intel_dp_link_traini= ng.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 i= ntel_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 inte= l_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, > > > > =A0=A0 Lyude Paul (she/her) > > > > =A0=A0 Software Engineer at Red Hat > > > > =A0=A0 = > > > > Note: I deal with a lot of emails and have a lot of bugs on my plat= e. 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 e= mail to > > > > check > > > > on my status. I don't bite! > > > > = > > > = > > = > > -- = > > 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. I= f you've > > asked me a question, are waiting for a review/merge on a patch, etc. an= d I > > haven't responded in a while, please feel free to send me another email= to 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