Re: [RFC PATCH v2 0/3] prerequisites for device reserved local mem rework

Laurentiu Tudor
2019-05-15T10:37:10Z

Hello,

On 14.05.2019 21:29, Fredrik Noring wrote:
> Thanks Robin!
>
>>> For HCs that have local memory, replace the current DMA API usage
>>> with a genalloc generic allocator to manage the mappings for these
>>> devices.
>>> This is in preparation for dropping the existing "coherent" dma
>>> mem declaration APIs. Current implementation was relying on a short
>>> circuit in the DMA API that in the end, was acting as an allocator
>>> for these type of devices.
>>>
>>> Only compiled tested, so any volunteers willing to test are most welcome.
>>
>> I recall an out-of-tree PlayStation 2 OHCI driver being another
>> HCD_LOCAL_MEM user - if Fredrik and Juergen are still active on that,
>> hopefully they might be able to comment on whether this approach can
>> work for them too. Patchwork link just in case:
>> https://patchwork.kernel.org/project/linux-usb/list/?series=117433
>
> True. In fact I'm preparing a patch submission for this PS2 OHCI driver,
> along with about a hundred other patches (unrelated to the USB subsystem).
> Hopefully in a few weeks. My patches are currently on top of v5.0. What
> branch/version is recommended to try this DMA update?

I think that any recent kernel will do, so I'd say your current branch
should be fine.

> Here is the v5.0.11 PS2 OHCI driver, for reference:
>
> https://github.com/frno7/linux/blob/ps2-v5.0.11/drivers/usb/host/ohci-ps2.c
Please note that the driver will need to be updated, see here for an
example:

https://patchwork.kernel.org/patch/10943105/

---
Best Regards, Lauretniu