From patchwork Wed Mar 8 15:52:52 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Rob Clark X-Patchwork-Id: 661370 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 59F91C6FD1E for ; Wed, 8 Mar 2023 15:53:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230096AbjCHPxh (ORCPT ); Wed, 8 Mar 2023 10:53:37 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34708 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231867AbjCHPxe (ORCPT ); Wed, 8 Mar 2023 10:53:34 -0500 Received: from mail-pj1-x1031.google.com (mail-pj1-x1031.google.com [IPv6:2607:f8b0:4864:20::1031]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 03AE35DCAD; Wed, 8 Mar 2023 07:53:32 -0800 (PST) Received: by mail-pj1-x1031.google.com with SMTP id h11-20020a17090a2ecb00b00237c740335cso2166424pjs.3; Wed, 08 Mar 2023 07:53:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1678290811; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=R7rI0HySL5zudRz4HuKhYN0exIGOWsfBmXbch8fe/1U=; b=ZZz9jOMZZuUhCof2k7IC+UxhUe78kx1LpuGivmR4e4F6P+7GlcN89ubaXkLjrfKacv dlaKNN9r2heQZqcwSWpova/LLu7CvdwPnFPha7q16bycW4EvUsJG7uEI0u2XDaK4nh0Z uvgkd+62Fa4fNTTYpAMPjznXTRUIjDgdRddJZbxocfPCJJyjr8SbpGIdoLfFwPyQmuYA 69w8qjSEhpF0GIu9IUXN/3hfbBfr2IqJWn389DfRXt41hND3MlgbfVTJAKMkSEIWVNvn n3Gx30RNuK50pKnuMjks5RxeuT7jMlBoWZDoPglK061udCdR46QJNmtG0BzyexE2NJSq VkMg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1678290811; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=R7rI0HySL5zudRz4HuKhYN0exIGOWsfBmXbch8fe/1U=; b=RPmWP4alOVFhMoXPN6mSGsYNkKCVtR23rcpKmYgO7eQWLUUjo8S4hjQMyL4vTIaCc2 BcNUmb/p62vOPWifHHJvoo5UFQzC8LdhshcoJqH+MMkmoeY7W+2qgfVMViaxNsGBr9o9 lvkDnYtZQCIxtGawr72ULDNpe7YpReEqRxkzcbxF+yEHfb17flcGaw8S820IKi4u1w3s aFk4cxvdV3aPq3jdA9dLu59pRfppQTNJlWZ1MeqOGbFhdYr1Cb5w0wSQqhM/n3mzGWTG OWJahms5sxQKjmXC248z+9WYIIRYYFS5NHRTZa1408uO7kZakuTm45uzwGn5LY4S0Fjg Hj8g== X-Gm-Message-State: AO0yUKVu2e5qR+LSo66KL0rT/XSpnoabiYwEdZRx5w5RfXpnLffySjGN 0GdNnBD9v1V4IOkt2yqExTE= X-Google-Smtp-Source: AK7set80iHNnuuwkVMvUGHiSUpjdHyNwKBVSG4gfwmLyorJB/wum7fkh3ST1L18jjlzpU+x15vlVMw== X-Received: by 2002:a05:6a20:4fa4:b0:cb:af96:9687 with SMTP id gh36-20020a056a204fa400b000cbaf969687mr14262670pzb.15.1678290811353; Wed, 08 Mar 2023 07:53:31 -0800 (PST) Received: from localhost ([2a00:79e1:abd:4a00:61b:48ed:72ab:435b]) by smtp.gmail.com with ESMTPSA id m22-20020aa78a16000000b005a8f1d76d46sm9844809pfa.13.2023.03.08.07.53.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Mar 2023 07:53:30 -0800 (PST) From: Rob Clark To: dri-devel@lists.freedesktop.org Cc: freedreno@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, Luben Tuikov , =?utf-8?q?Christian_K=C3=B6nig?= , Rodrigo Vivi , Matt Turner , Bas Nieuwenhuizen , Rob Clark , =?utf-8?q?Christian_K=C3=B6nig?= , Pekka Paalanen , Bagas Sanjaya , Sumit Semwal , Jonathan Corbet , Gustavo Padovan , linux-media@vger.kernel.org (open list:DMA BUFFER SHARING FRAMEWORK), linaro-mm-sig@lists.linaro.org (moderated list:DMA BUFFER SHARING FRAMEWORK), linux-doc@vger.kernel.org (open list:DOCUMENTATION), linux-kernel@vger.kernel.org (open list) Subject: [PATCH v10 01/15] dma-buf/dma-fence: Add deadline awareness Date: Wed, 8 Mar 2023 07:52:52 -0800 Message-Id: <20230308155322.344664-2-robdclark@gmail.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230308155322.344664-1-robdclark@gmail.com> References: <20230308155322.344664-1-robdclark@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org From: Rob Clark Add a way to hint to the fence signaler of an upcoming deadline, such as vblank, which the fence waiter would prefer not to miss. This is to aid the fence signaler in making power management decisions, like boosting frequency as the deadline approaches and awareness of missing deadlines so that can be factored in to the frequency scaling. v2: Drop dma_fence::deadline and related logic to filter duplicate deadlines, to avoid increasing dma_fence size. The fence-context implementation will need similar logic to track deadlines of all the fences on the same timeline. [ckoenig] v3: Clarify locking wrt. set_deadline callback v4: Clarify in docs comment that this is a hint v5: Drop DMA_FENCE_FLAG_HAS_DEADLINE_BIT. v6: More docs v7: Fix typo, clarify past deadlines Signed-off-by: Rob Clark Reviewed-by: Christian König Acked-by: Pekka Paalanen Reviewed-by: Bagas Sanjaya --- Documentation/driver-api/dma-buf.rst | 6 +++ drivers/dma-buf/dma-fence.c | 59 ++++++++++++++++++++++++++++ include/linux/dma-fence.h | 22 +++++++++++ 3 files changed, 87 insertions(+) diff --git a/Documentation/driver-api/dma-buf.rst b/Documentation/driver-api/dma-buf.rst index 622b8156d212..183e480d8cea 100644 --- a/Documentation/driver-api/dma-buf.rst +++ b/Documentation/driver-api/dma-buf.rst @@ -164,6 +164,12 @@ DMA Fence Signalling Annotations .. kernel-doc:: drivers/dma-buf/dma-fence.c :doc: fence signalling annotation +DMA Fence Deadline Hints +~~~~~~~~~~~~~~~~~~~~~~~~ + +.. kernel-doc:: drivers/dma-buf/dma-fence.c + :doc: deadline hints + DMA Fences Functions Reference ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c index 0de0482cd36e..f177c56269bb 100644 --- a/drivers/dma-buf/dma-fence.c +++ b/drivers/dma-buf/dma-fence.c @@ -912,6 +912,65 @@ dma_fence_wait_any_timeout(struct dma_fence **fences, uint32_t count, } EXPORT_SYMBOL(dma_fence_wait_any_timeout); +/** + * DOC: deadline hints + * + * In an ideal world, it would be possible to pipeline a workload sufficiently + * that a utilization based device frequency governor could arrive at a minimum + * frequency that meets the requirements of the use-case, in order to minimize + * power consumption. But in the real world there are many workloads which + * defy this ideal. For example, but not limited to: + * + * * Workloads that ping-pong between device and CPU, with alternating periods + * of CPU waiting for device, and device waiting on CPU. This can result in + * devfreq and cpufreq seeing idle time in their respective domains and in + * result reduce frequency. + * + * * Workloads that interact with a periodic time based deadline, such as double + * buffered GPU rendering vs vblank sync'd page flipping. In this scenario, + * missing a vblank deadline results in an *increase* in idle time on the GPU + * (since it has to wait an additional vblank period), sending a signal to + * the GPU's devfreq to reduce frequency, when in fact the opposite is what is + * needed. + * + * To this end, deadline hint(s) can be set on a &dma_fence via &dma_fence_set_deadline. + * The deadline hint provides a way for the waiting driver, or userspace, to + * convey an appropriate sense of urgency to the signaling driver. + * + * A deadline hint is given in absolute ktime (CLOCK_MONOTONIC for userspace + * facing APIs). The time could either be some point in the future (such as + * the vblank based deadline for page-flipping, or the start of a compositor's + * composition cycle), or the current time to indicate an immediate deadline + * hint (Ie. forward progress cannot be made until this fence is signaled). + * + * Multiple deadlines may be set on a given fence, even in parallel. See the + * documentation for &dma_fence_ops.set_deadline. + * + * The deadline hint is just that, a hint. The driver that created the fence + * may react by increasing frequency, making different scheduling choices, etc. + * Or doing nothing at all. + */ + +/** + * dma_fence_set_deadline - set desired fence-wait deadline hint + * @fence: the fence that is to be waited on + * @deadline: the time by which the waiter hopes for the fence to be + * signaled + * + * Give the fence signaler a hint about an upcoming deadline, such as + * vblank, by which point the waiter would prefer the fence to be + * signaled by. This is intended to give feedback to the fence signaler + * to aid in power management decisions, such as boosting GPU frequency + * if a periodic vblank deadline is approaching but the fence is not + * yet signaled.. + */ +void dma_fence_set_deadline(struct dma_fence *fence, ktime_t deadline) +{ + if (fence->ops->set_deadline && !dma_fence_is_signaled(fence)) + fence->ops->set_deadline(fence, deadline); +} +EXPORT_SYMBOL(dma_fence_set_deadline); + /** * dma_fence_describe - Dump fence describtion into seq_file * @fence: the 6fence to describe diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h index 775cdc0b4f24..d54b595a0fe0 100644 --- a/include/linux/dma-fence.h +++ b/include/linux/dma-fence.h @@ -257,6 +257,26 @@ struct dma_fence_ops { */ void (*timeline_value_str)(struct dma_fence *fence, char *str, int size); + + /** + * @set_deadline: + * + * Callback to allow a fence waiter to inform the fence signaler of + * an upcoming deadline, such as vblank, by which point the waiter + * would prefer the fence to be signaled by. This is intended to + * give feedback to the fence signaler to aid in power management + * decisions, such as boosting GPU frequency. + * + * This is called without &dma_fence.lock held, it can be called + * multiple times and from any context. Locking is up to the callee + * if it has some state to manage. If multiple deadlines are set, + * the expectation is to track the soonest one. If the deadline is + * before the current time, it should be interpreted as an immediate + * deadline. + * + * This callback is optional. + */ + void (*set_deadline)(struct dma_fence *fence, ktime_t deadline); }; void dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops, @@ -583,6 +603,8 @@ static inline signed long dma_fence_wait(struct dma_fence *fence, bool intr) return ret < 0 ? ret : 0; } +void dma_fence_set_deadline(struct dma_fence *fence, ktime_t deadline); + struct dma_fence *dma_fence_get_stub(void); struct dma_fence *dma_fence_allocate_private_stub(void); u64 dma_fence_context_alloc(unsigned num);