From patchwork Fri Nov 8 10:35:11 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Wilson X-Patchwork-Id: 11234529 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id CB6241850 for ; Fri, 8 Nov 2019 10:35:19 +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 B3B8F21848 for ; Fri, 8 Nov 2019 10:35:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B3B8F21848 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 0FBD76F927; Fri, 8 Nov 2019 10:35:19 +0000 (UTC) X-Original-To: intel-gfx@lists.freedesktop.org Delivered-To: intel-gfx@lists.freedesktop.org Received: from fireflyinternet.com (mail.fireflyinternet.com [109.228.58.192]) by gabe.freedesktop.org (Postfix) with ESMTPS id 189446F924 for ; Fri, 8 Nov 2019 10:35:15 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from haswell.alporthouse.com (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP id 19126204-1500050 for ; Fri, 08 Nov 2019 10:35:11 +0000 From: Chris Wilson To: intel-gfx@lists.freedesktop.org Date: Fri, 8 Nov 2019 10:35:11 +0000 Message-Id: <20191108103511.20951-2-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191108103511.20951-1-chris@chris-wilson.co.uk> References: <20191108103511.20951-1-chris@chris-wilson.co.uk> MIME-Version: 1.0 Subject: [Intel-gfx] [CI 2/2] drm/i915/pmu: Only use exclusive mmio access for gen7 X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On gen7, we have to avoid concurrent access to the same mmio cacheline, and so coordinate all mmio access with the uncore->lock. However, for pmu, we want to avoid perturbing the system and disabling interrupts unnecessarily, so restrict the w/a to gen7 where it is requied to prevent machine hangs. Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Reviewed-by: Tvrtko Ursulin --- drivers/gpu/drm/i915/i915_pmu.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c index 8e74f40413b8..4804775644bf 100644 --- a/drivers/gpu/drm/i915/i915_pmu.c +++ b/drivers/gpu/drm/i915/i915_pmu.c @@ -292,6 +292,16 @@ add_sample(struct i915_pmu_sample *sample, u32 val) sample->cur += val; } +static bool exclusive_mmio_access(const struct drm_i915_private *i915) +{ + /* + * We have to avoid concurrent mmio cache line access on gen7 or + * risk a machine hang. For a fun history lesson dig out the old + * userspace intel_gpu_top and run it on Ivybridge or Haswell! + */ + return IS_GEN(i915, 7); +} + static void engines_sample(struct intel_gt *gt, unsigned int period_ns) { @@ -304,6 +314,7 @@ engines_sample(struct intel_gt *gt, unsigned int period_ns) for_each_engine(engine, gt, id) { struct intel_engine_pmu *pmu = &engine->pmu; + spinlock_t *mmio_lock; unsigned long flags; bool busy; u32 val; @@ -311,7 +322,12 @@ engines_sample(struct intel_gt *gt, unsigned int period_ns) if (!intel_engine_pm_get_if_awake(engine)) continue; - spin_lock_irqsave(&engine->uncore->lock, flags); + mmio_lock = NULL; + if (exclusive_mmio_access(i915)) + mmio_lock = &engine->uncore->lock; + + if (unlikely(mmio_lock)) + spin_lock_irqsave(mmio_lock, flags); val = ENGINE_READ_FW(engine, RING_CTL); if (val == 0) /* powerwell off => engine idle */ @@ -342,7 +358,8 @@ engines_sample(struct intel_gt *gt, unsigned int period_ns) add_sample(&pmu->sample[I915_SAMPLE_BUSY], period_ns); skip: - spin_unlock_irqrestore(&engine->uncore->lock, flags); + if (unlikely(mmio_lock)) + spin_unlock_irqrestore(mmio_lock, flags); intel_engine_pm_put(engine); } }