From patchwork Fri Feb 5 00:04:37 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Wilson X-Patchwork-Id: 12069019 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=-16.7 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,USER_AGENT_GIT 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 C100FC433DB for ; Fri, 5 Feb 2021 00:04:52 +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 1650E64FB3 for ; Fri, 5 Feb 2021 00:04:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1650E64FB3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=chris-wilson.co.uk 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 9B4036E150; Fri, 5 Feb 2021 00:04:51 +0000 (UTC) Received: from fireflyinternet.com (unknown [77.68.26.236]) by gabe.freedesktop.org (Postfix) with ESMTPS id EB6F46E150 for ; Fri, 5 Feb 2021 00:04:49 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.69.177; Received: from build.alporthouse.com (unverified [78.156.69.177]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP id 23792181-1500050 for multiple; Fri, 05 Feb 2021 00:04:39 +0000 From: Chris Wilson To: intel-gfx@lists.freedesktop.org Date: Fri, 5 Feb 2021 00:04:37 +0000 Message-Id: <20210205000437.16079-1-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH] drm/i915/selftest: Synchronise with the GPU timestamp 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: Chris Wilson Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Wait for the GPU to wake up from the semaphore before measuring the time, so that we coordinate the sampling on both the CPU and GPU for more accurate comparisons. Reported-by: Bruce Chang Signed-off-by: Chris Wilson Cc: CQ Tang Reviewed-by: Bruce Chang --- drivers/gpu/drm/i915/gt/selftest_engine_pm.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/gt/selftest_engine_pm.c b/drivers/gpu/drm/i915/gt/selftest_engine_pm.c index 3ce8cb3329f3..007a7c790778 100644 --- a/drivers/gpu/drm/i915/gt/selftest_engine_pm.c +++ b/drivers/gpu/drm/i915/gt/selftest_engine_pm.c @@ -111,8 +111,10 @@ static int __measure_timestamps(struct intel_context *ce, /* Run the request for a 100us, sampling timestamps before/after */ preempt_disable(); - *dt = local_clock(); write_semaphore(&sema[2], 0); + while (READ_ONCE(sema[1]) == 0) /* wait for the gpu to catch up */ + cpu_relax(); + *dt = local_clock(); udelay(100); *dt = local_clock() - *dt; write_semaphore(&sema[2], 1);