Re: [RESEND PATCH V12 XDMA 1/2] dmaengine: xilinx: xdma: Add xilinx xdma driver

From: Lizhi Hou
Date: Tue Feb 21 2023 - 22:52:06 EST



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@xxxxxxxxxx> 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@xxxxxxxxxx/

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