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Tue, 31 Aug 2021 06:31:29 +0000 Subject: Re: [PATCH] dma-buf: heaps: remove duplicated cache sync To: guangming.cao@mediatek.com Cc: Brian.Starkey@arm.com, benjamin.gaignard@linaro.org, dri-devel@lists.freedesktop.org, john.stultz@linaro.org, labbott@redhat.com, linaro-mm-sig@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linux-mediatek@lists.infradead.org, lmark@codeaurora.org, matthias.bgg@gmail.com, sumit.semwal@linaro.org, wsd_upstream@mediatek.com References: <20210831034405.41916-1-guangming.cao@mediatek.com> From: =?UTF-8?Q?Christian_K=c3=b6nig?= Message-ID: <0b48df29-a20f-65f6-bc4c-6c0a7522ecd7@amd.com> Date: Tue, 31 Aug 2021 08:31:22 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 In-Reply-To: <20210831034405.41916-1-guangming.cao@mediatek.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-ClientProxiedBy: AM0PR02CA0181.eurprd02.prod.outlook.com (2603:10a6:20b:28e::18) To MN2PR12MB3775.namprd12.prod.outlook.com (2603:10b6:208:159::19) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [192.168.178.21] (91.14.161.181) by AM0PR02CA0181.eurprd02.prod.outlook.com (2603:10a6:20b:28e::18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4457.21 via Frontend Transport; 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Could you tell me more about it? Yes, that's correct and all of those needs to be synced as far as I know. See the dma_sync_sgtable_for_cpu() is intentionally for each SG table given out. >>> Is there any case that attachments of one dmabuf will points to >>> different memory? If not, seems do sync only one time is more better. >> I think that this can happen, yes. >> >> Christian. >> > Seems it's a very special case on Android, if you don't mind, could you > tell me more about it? That might be the case, nevertheless this change here is illegal from the DMA API point of view as far as I can see. Regards, Christian. > >>> Signed-off-by: Guangming Cao >>> --- >>> drivers/dma-buf/heaps/system_heap.c | 14 ++++++++------ >>> 1 file changed, 8 insertions(+), 6 deletions(-) >>> >>> diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c >>> index 23a7e74ef966..909ef652a8c8 100644 >>> --- a/drivers/dma-buf/heaps/system_heap.c >>> +++ b/drivers/dma-buf/heaps/system_heap.c >>> @@ -162,9 +162,10 @@ static int system_heap_dma_buf_begin_cpu_access(struct dma_buf *dmabuf, >>> invalidate_kernel_vmap_range(buffer->vaddr, buffer->len); >>> >>> list_for_each_entry(a, &buffer->attachments, list) { >>> - if (!a->mapped) >>> - continue; >>> - dma_sync_sgtable_for_cpu(a->dev, a->table, direction); >>> + if (a->mapped) { >>> + dma_sync_sgtable_for_cpu(a->dev, a->table, direction); >>> + break; >>> + } >>> } >>> mutex_unlock(&buffer->lock); >>> >>> @@ -183,9 +184,10 @@ static int system_heap_dma_buf_end_cpu_access(struct dma_buf *dmabuf, >>> flush_kernel_vmap_range(buffer->vaddr, buffer->len); >>> >>> list_for_each_entry(a, &buffer->attachments, list) { >>> - if (!a->mapped) >>> - continue; >>> - dma_sync_sgtable_for_device(a->dev, a->table, direction); >>> + if (!a->mapped) { >>> + dma_sync_sgtable_for_device(a->dev, a->table, direction); >>> + break; >>> + } >>> } >>> mutex_unlock(&buffer->lock); >>>