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=-9.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 173A7C43457 for ; Fri, 16 Oct 2020 07:08:45 +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 C139620720 for ; Fri, 16 Oct 2020 07:08:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C139620720 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.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 3CE196EA7B; Fri, 16 Oct 2020 07:08:44 +0000 (UTC) Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by gabe.freedesktop.org (Postfix) with ESMTPS id 28B216EA7B for ; Fri, 16 Oct 2020 07:08:43 +0000 (UTC) IronPort-SDR: QTS5cXdFrOMGUAsMRQcw94Gr5OHh2Oox6nlSNdnDJrNZyhXSdI/6+yctXlOzLnwQjGsxarBmya 7FxH05ATLvHA== X-IronPort-AV: E=McAfee;i="6000,8403,9775"; a="166611388" X-IronPort-AV: E=Sophos;i="5.77,382,1596524400"; d="scan'208";a="166611388" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Oct 2020 00:08:42 -0700 IronPort-SDR: oNYv+ZCWfOZJTHTvVgrQL/CZUWkcwDpzFhupKVOTkiKTrCT9RTCONyY16nL8F6beeqoeX00VWa DdUl2+F02M+w== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.77,382,1596524400"; d="scan'208";a="357292343" Received: from gaia.fi.intel.com ([10.237.72.192]) by FMSMGA003.fm.intel.com with ESMTP; 16 Oct 2020 00:08:40 -0700 Received: by gaia.fi.intel.com (Postfix, from userid 1000) id 3A89E5C2038; Fri, 16 Oct 2020 10:07:07 +0300 (EEST) From: Mika Kuoppala To: Chris Wilson , intel-gfx@lists.freedesktop.org In-Reply-To: <20201015195023.32346-1-chris@chris-wilson.co.uk> References: <20201015195023.32346-1-chris@chris-wilson.co.uk> Date: Fri, 16 Oct 2020 10:07:07 +0300 Message-ID: <87eelysl7o.fsf@gaia.fi.intel.com> MIME-Version: 1.0 Subject: Re: [Intel-gfx] [PATCH] drm/i915/gt: Delay execlist processing for tgl 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: , Cc: stable@vger.kernel.org, Chris Wilson Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Chris Wilson writes: > When running gem_exec_nop, it floods the system with many requests (with > the goal of userspace submitting faster than the HW can process a single > empty batch). This causes the driver to continually resubmit new > requests onto the end of an active context, a flood of lite-restore > preemptions. If we time this just right, Tigerlake hangs. > > Inserting a small delay between the processing of CS events and > submitting the next context, prevents the hang. Naturally it does not > occur with debugging enabled. The suspicion then is that this is related > to the issues with the CS event buffer, and inserting an mmio read of > the CS pointer status appears to be very successful in preventing the > hang. Other registers, or uncached reads, or plain mb, do not prevent > the hang, suggesting that register is key -- but that the hang can be > prevented by a simple udelay, suggests it is just a timing issue like > that encountered by commit 233c1ae3c83f ("drm/i915/gt: Wait for CSB > entries on Tigerlake"). Also note that the hang is not prevented by > applying CTX_DESC_FORCE_RESTORE, or by inserting a delay on the GPU > between requests. > > Signed-off-by: Chris Wilson > Cc: Mika Kuoppala > Cc: Bruce Chang > Cc: Joonas Lahtinen > Cc: stable@vger.kernel.org Acked-by: Mika Kuoppala > --- > drivers/gpu/drm/i915/gt/intel_lrc.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c > index 6170f6874f52..d15d561152ba 100644 > --- a/drivers/gpu/drm/i915/gt/intel_lrc.c > +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c > @@ -2711,6 +2711,9 @@ static void process_csb(struct intel_engine_cs *engine) > smp_wmb(); /* complete the seqlock */ > WRITE_ONCE(execlists->active, execlists->inflight); > > + /* Magic delay for tgl */ > + ENGINE_POSTING_READ(engine, RING_CONTEXT_STATUS_PTR); > + > WRITE_ONCE(execlists->pending[0], NULL); > } else { > if (GEM_WARN_ON(!*execlists->active)) { > -- > 2.20.1 _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx