Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
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: <dd5ba603-8c9d-f6a0-cbcc-dfb353fb6701@amd.com>
 <20210831034405.41916-1-guangming.cao@mediatek.com>
From:   =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>
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
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; Tue, 31 Aug 2021 06:31:26 +0000
X-MS-PublicTrafficType: Email
X-MS-Office365-Filtering-Correlation-Id: 6205f434-79cc-466d-18da-08d96c48f705
X-MS-TrafficTypeDiagnostic: MN2PR12MB3903:
X-Microsoft-Antispam-PRVS: <MN2PR12MB3903F9AF510AEB4E2E88CBF083CC9@MN2PR12MB3903.namprd12.prod.outlook.com>
X-MS-Oob-TLC-OOBClassifiers: OLM:9508;
X-MS-Exchange-SenderADCheck: 1
X-MS-Exchange-AntiSpam-Relay: 0
X-Microsoft-Antispam: BCL:0;
X-Microsoft-Antispam-Message-Info: 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
X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:MN2PR12MB3775.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(396003)(136003)(366004)(346002)(39860400002)(376002)(4326008)(6666004)(6916009)(86362001)(83380400001)(66556008)(66946007)(6486002)(5660300002)(66476007)(36756003)(2906002)(16576012)(31686004)(478600001)(38100700002)(2616005)(316002)(26005)(8936002)(31696002)(8676002)(956004)(7416002)(186003)(43740500002)(45980500001);DIR:OUT;SFP:1101;
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?TmhoQXlpSU9mUlByNmw3d0tKSUk1cFZ3a2xKY1RPVjY1TTZNeGpRcU5pWWJh?=
 =?utf-8?B?ckFYMWtIZnphYW1rUGpHci9EM09mbFdpWW1rYXp6aXgvaDd1SGYvOEwzZFVv?=
 =?utf-8?B?UzFvd2hTdEx3a2d2RnhzZ0NuemZWWUIxN2NCR1JEMkZDVGdBYVdHRFZJRGZr?=
 =?utf-8?B?WHhIWlNUNHJzbTBUSmFDQUNuWHVMazFoTC9GT2FmTmpRTmJQOVUwZExjUHFp?=
 =?utf-8?B?TXRsV2RVaE4zbW1TZnUvZzdJZWM4bUxNMDhIb3p1SEp3SzZhSjVJUTl5VHAv?=
 =?utf-8?B?QnVqQWR1SUEvcGtvTlc2bUQzNVAxVnBwcmJlTWlHWW9JdUpreDJVT0I0RWhq?=
 =?utf-8?B?RTB2aGtRR2dWTU1NNjVaNWh2R05uVG91REFHaUZ1U0dZU2JkZlhrVmd5R3o2?=
 =?utf-8?B?c3VuZE1mc2JKMjl0LzdncHA4eEFna1BZSFNVb2VOVm1iY094R2U2ckJYMnEw?=
 =?utf-8?B?ZlBhVnlxc3FleHhvUXIxTDdCZ3FreDZvbkxBNml6ZTZ6dXFrNVFWZldId29x?=
 =?utf-8?B?b01nWkcrWXFlY04yNjlzMWtTdVBXTDU3N2VGVjZ0UFJrMnp1ZDNOMTZFZG1i?=
 =?utf-8?B?Zi94bU5DaW1oeWoyeW4zVjQzaUY3bWxmN3BCb3hLbWV5NkR3ditDVmdnQmdU?=
 =?utf-8?B?c2dhT0VyU2JJbk94TUFYNFRaTEQxZkd6S3Z2U3BoOVlpUk95QkNVbjNKbjhr?=
 =?utf-8?B?QVJLTVhyZ0luVXYvK3lZUTIyMm9kd3A5cHNXZTVTdkoxdkZ0Y0w5cUVyN2U3?=
 =?utf-8?B?bHBEVlBxcUZzbCt1YUN3K2tvWGtEWXNCRFVaT1J5VVNJZ1ZPRDhMQ085RUd2?=
 =?utf-8?B?eVJpZ0NmRkYzZFJ6MlU0b2NKeS9LMzR3ZG5DaXRFRXdpbkZhK2I0aTFPWk8x?=
 =?utf-8?B?ckwwWEhoaktpZGI5YnNKMWhkZXJKMnczNlFOYVB6OFhQYkxTOVJrTkNYc1RG?=
 =?utf-8?B?aXN6RTF2WmVMVkY2d2k2S2x5dC9VRE96OFZBQ0FtR2Y1YUN1VkpLWkg5R0ts?=
 =?utf-8?B?NmpvUlNteWxubFpqWWtvSDdXOGRSY2l1ZGw2MzJSOHFFSHdidnBnNjI2RnVH?=
 =?utf-8?B?a2VEek82WnFsbHNOY200b0g4c25CS3lzSEpjRzVicXN1MFJ5TEk1TTlRY1RU?=
 =?utf-8?B?MkJHMS96Y0F1bHFpQ1paY2lBN05uODROckZxaVNzVmUva2RaYVdEamVPYWVz?=
 =?utf-8?B?Z0JMQnlBellPZStkdUxmSmN2T1ZPZHRoVVZjMlVwckhrQzI2ZDFPMkZjcVov?=
 =?utf-8?B?cEV5SisyK3VEdXhTZ0pXc3RycStUbFV3UkI1VFJmV3Q2b2RienZ2UkprenVG?=
 =?utf-8?B?eVUrRWx5aGRPTm5teCthb0E0aCs2N2JkUE1ucmVYZHlOaTRYMjRldTNGblVK?=
 =?utf-8?B?WkFKaUZLc0p0TEJxQ3dON29scmhOa3Z5eUlYV2V1T1RnN3JYUm1lOGU2ekln?=
 =?utf-8?B?V0FGaDQrK1ZaaTV4OXNENGF5Rk8ycWJWM1A0YjVHMzAycnAyY2gwU0dGOWlp?=
 =?utf-8?B?WWZHdlVXU1pWaHZWb3BXU3B3SkR1MW1uSUNScjFTemY3czJIVkhudkRYc3da?=
 =?utf-8?B?V1Jhd1p0S2dwZzNZeTdCUDN4MVhUbFM3WG1QR05KdktLZnhPbGtBZHJJYmcx?=
 =?utf-8?B?SlUwbkR4dEpYeFlueVdlR1I4bGlESU52NUpBenVjb3NBRGRYV1VRVEIxUnhX?=
 =?utf-8?B?dHNOdWpHak9VVUpibEs5UGdkL3FBKzc0TkIzbjQxQWFwSVB3eC9HUUFlcndq?=
 =?utf-8?Q?UgwkTAq+AKtr8dnGoQ/LBZ5tJcDnMaAgC+Zz/At?=
X-OriginatorOrg: amd.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 6205f434-79cc-466d-18da-08d96c48f705
X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB3775.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 31 Aug 2021 06:31:29.7341
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: qte71PpFY1gxU8vMv8x0qnu6OwUUq0AvQ9HlP8BiczGzU3JwZY6upp6ixCef9jv0
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR12MB3903
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Am 31.08.21 um 05:44 schrieb guangming.cao@mediatek.com:
> From: Guangming Cao <Guangming.Cao@mediatek.com>
>
>> Am 30.08.21 um 12:01 schrieb guangming.cao@mediatek.com:
>>> From: Guangming Cao <Guangming.Cao@mediatek.com>
>>>
>>> Current flow, one dmabuf maybe call cache sync many times if
>>> it has beed mapped more than one time.
>> Well I'm not an expert on DMA heaps, but this will most likely not work
>> correctly.
>>
> All attachments of one dmabuf will add into a list, I think it means dmabuf
> supports map more than one time. 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 <Guangming.Cao@mediatek.com>
>>> ---
>>>    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);
>>>