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Tue, 13 Oct 2020 13:53:40 GMT Sender: akhilpo=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 12D1EC433CB; Tue, 13 Oct 2020 13:53:40 +0000 (UTC) Received: from [192.168.1.9] (unknown [117.210.177.99]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: akhilpo) by smtp.codeaurora.org (Postfix) with ESMTPSA id 5BD99C433F1; Tue, 13 Oct 2020 13:53:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 5BD99C433F1 Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=fail smtp.mailfrom=akhilpo@codeaurora.org Subject: Re: [2/2] drm/msm: Add support for GPU cooling To: mka@chromium.org Cc: linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@freedesktop.org, freedreno@lists.freedesktop.org References: <1602176947-17385-2-git-send-email-akhilpo@codeaurora.org> <20201009183640.GB1292413@google.com> <20201012174035.GA44627@google.com> From: Akhil P Oommen Message-ID: <80ded484-a058-70fc-be9d-045be2933563@codeaurora.org> Date: Tue, 13 Oct 2020 19:23:34 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.3.1 MIME-Version: 1.0 In-Reply-To: <20201012174035.GA44627@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On 10/12/2020 11:10 PM, mka@chromium.org wrote: > On Mon, Oct 12, 2020 at 07:03:51PM +0530, Akhil P Oommen wrote: >> On 10/10/2020 12:06 AM, mka@chromium.org wrote: >>> Hi Akhil, >>> >>> On Thu, Oct 08, 2020 at 10:39:07PM +0530, Akhil P Oommen wrote: >>>> Register GPU as a devfreq cooling device so that it can be passively >>>> cooled by the thermal framework. >>>> >>>> Signed-off-by: Akhil P Oommen >>>> --- >>>> drivers/gpu/drm/msm/msm_gpu.c | 13 ++++++++++++- >>>> drivers/gpu/drm/msm/msm_gpu.h | 2 ++ >>>> 2 files changed, 14 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c >>>> index 55d1648..93ffd66 100644 >>>> --- a/drivers/gpu/drm/msm/msm_gpu.c >>>> +++ b/drivers/gpu/drm/msm/msm_gpu.c >>>> @@ -14,6 +14,7 @@ >>>> #include >>>> #include >>>> #include >>>> +#include >>>> #include >>>> #include >>>> @@ -107,9 +108,18 @@ static void msm_devfreq_init(struct msm_gpu *gpu) >>>> if (IS_ERR(gpu->devfreq.devfreq)) { >>>> DRM_DEV_ERROR(&gpu->pdev->dev, "Couldn't initialize GPU devfreq\n"); >>>> gpu->devfreq.devfreq = NULL; >>>> + return; >>>> } >>>> devfreq_suspend_device(gpu->devfreq.devfreq); >>>> + >>>> + gpu->cooling = of_devfreq_cooling_register(gpu->pdev->dev.of_node, >>>> + gpu->devfreq.devfreq); >>>> + if (IS_ERR(gpu->cooling)) { >>>> + DRM_DEV_ERROR(&gpu->pdev->dev, >>>> + "Couldn't register GPU cooling device\n"); >>>> + gpu->cooling = NULL; >>>> + } >>>> } >>>> static int enable_pwrrail(struct msm_gpu *gpu) >>>> @@ -926,7 +936,6 @@ int msm_gpu_init(struct drm_device *drm, struct platform_device *pdev, >>>> msm_devfreq_init(gpu); >>>> - Will remove this unintended change. >>>> gpu->aspace = gpu->funcs->create_address_space(gpu, pdev); >>>> if (gpu->aspace == NULL) >>>> @@ -1005,4 +1014,6 @@ void msm_gpu_cleanup(struct msm_gpu *gpu) >>>> gpu->aspace->mmu->funcs->detach(gpu->aspace->mmu); >>>> msm_gem_address_space_put(gpu->aspace); >>>> } >>>> + >>>> + devfreq_cooling_unregister(gpu->cooling); >>> >>> Resources should be released in reverse order, otherwise the cooling device >>> could use resources that have already been freed. >>> Why do you think this is not the correct order? If you are thinking >> about devfreq struct, it is managed device resource. > > I did not check specifically if changing the frequency really uses any of the > resources that are released previously, In any case it's not a good idea to > allow other parts of the kernel to use a half initialized/torn down device. > Even if it isn't a problem today someone could change the driver to use any > of these resources (or add a new one) in a frequency change, without even > thinking about the cooling device, just (rightfully) asuming that things are > set up and torn down in a sane order. 'sane order' relative to what specifically here? Should we worry about freq change at this point because we have already disabled gpu runtime pm and devfreq? -Akhil. > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel > -Akhil.