Received-SPF: Pass (protection.outlook.com: domain of amd.com designates
 165.204.84.17 as permitted sender) receiver=protection.outlook.com;
 client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C
Message-ID: <6da2e72c-661c-e4de-f563-e06f045414ae@amd.com>
Date:   Tue, 21 Feb 2023 19:51:56 -0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.11.0
Subject: Re: [RESEND PATCH V12 XDMA 1/2] dmaengine: xilinx: xdma: Add xilinx
 xdma driver
Content-Language: en-US
To:     =?UTF-8?Q?Martin_T=c5=afma?= <tumic@gpxsee.org>,
        Geert Uytterhoeven <geert@linux-m68k.org>
CC:     <vkoul@kernel.org>, <dmaengine@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <max.zhen@amd.com>,
        <sonal.santan@amd.com>, <larry.liu@amd.com>, <brian.xu@amd.com>
References: <1675969514-3137-1-git-send-email-lizhi.hou@amd.com>
 <1675969514-3137-2-git-send-email-lizhi.hou@amd.com>
 <CAMuHMdXsUPAW5zKrsaTR9Tgv7kFdkz8s_QUjLXq6zDpoo47fRA@mail.gmail.com>
 <0f1aafa2-7495-163b-523a-f634bacc4b1f@gpxsee.org>
 <CAMuHMdUVkbPf1a8cW+zY1HwD83tm_m0L7Ufy=GO-RQB-AF_15A@mail.gmail.com>
 <aeb43671-57fd-654a-8e8d-d14ebb7f4083@gpxsee.org>
From:   Lizhi Hou <lizhi.hou@amd.com>
In-Reply-To: <aeb43671-57fd-654a-8e8d-d14ebb7f4083@gpxsee.org>
Content-Type: text/plain; charset="UTF-8"; format=flowed
Content-Transfer-Encoding: 8bit
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Feb 2023 03:51:57.8201
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 71accfcb-c39f-4f64-20b8-08db1488256e
X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com]
X-MS-Exchange-CrossTenant-AuthSource: DS1PEPF0000E639.namprd02.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB7913
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


On 2/21/23 13:46, Martin Tůma wrote:
> On 21. 02. 23 22:06, Geert Uytterhoeven wrote:
>> Hi Martin,
>>
>> On Tue, Feb 21, 2023 at 9:45 PM Martin Tůma <tumic@gpxsee.org> wrote:
>>> On 21. 02. 23 14:25, Geert Uytterhoeven wrote:
>>>> No platform dependencies at all, while this is a platform driver that
>>>> relies on some other not-yet-existing driver creating an "xdma"
>>>> platform device?
>>>
>>> There is at least one "already-existing" driver based on this driver
>>> that is waiting in the v4l2 queue for xdma - our MGB4 driver:
>>> https://patchwork.kernel.org/project/linux-media/patch/20230207150119.5542-2-tumic@gpxsee.org/ 
>>>
>>
>> Thanks for the link!
>>
>> As VIDEO_MGB4 selects XILINX_XDMA, perhaps XILINX_XDMA
>> can be made invisible, unless compile-testing?
>>
>>      config XILINX_XDMA
>>          tristate "Xilinx DMA/Bridge Subsystem DMA Engine" if 
>> COMPILE_TEST
>>
>> Gr{oetje,eeting}s,
>>
>>                          Geert
>>
>
> Hi,
> I think that the XDMA driver will always be used by a superior PCIe 
> card driver like in our case (mgb4) and using it separately makes no 
> sense/is not possible, so disabling it until some of the superior 
> drivers selects it makes sense for me. But what about out-of-the-tree 
> modules based on xdma? Making the module "invisible" will make compile 
> them much harder I guess? And there will be proprietary drivers based 
> on xdma, see Xilinx XRT: 
> https://github.com/houlz0507/XRT-1/tree/xdma_v4_usage
>
> The xdma authors from Xilinx will definitely give you a more 
> authoritative answer. I'm just a "random" user of the xdma module. 
> Originally our mgb4 driver was based on our own xdma sub-driver (in 
> turn based on some old "test" driver from Xilinx) which I was glad we 
> could abandon when this xdma driver has appeared. I helped the xdma 
> module to become usable for PCIe cards like our v4l2 grabber, but the 
> original intents of the xdma driver are unknown to me. If it is XRT, 
> than Xilinx will probably like the module to stay visible.
>
> M.
>
There are PCIe devices which use the XDMA IP and would use this xdma 
driver. Out of tree drivers for Xilinx/AMD Alveo devices can switch to 
this in kernel xdma driver.


Thanks,

Lizhi