Re: [PATCH v2 0/3] add dma noncoherent API

[Xu Yang]

On Fri, Jun 27, 2025 at 02:25:41PM +0300, Andy Shevchenko wrote:
> On Fri, Jun 27, 2025 at 06:19:36PM +0800, Xu Yang wrote:
> > On architectures where there is no coherent caching such as ARM it's
> > proved that using dma_alloc_noncontiguous API and handling manually
> 
> dma_alloc_noncontiguous()

Okay.

> 
> > the cache flushing will significantly improve performance.
> 
> > Refer to:
> > commit 20e1dbf2bbe2 ("media: uvcvideo: Use dma_alloc_noncontiguous API")
> > commit 68d0c3311ec1 ("media: stk1160: use dma_alloc_noncontiguous API")
> > 
> > However, it's obvious that there is significant code duplication between
> > these two commits. Beside, a potential user USB Monitor may read outdated
> > data before the driver do dma sync for cpu which will make the data
> 
> DMA
> CPU

Okay.

> 
> > unreliable.
> > 
> > To reduce code duplication and avoid USB Monitor result unreliable, this
> > series will introduce dma noncoherent API to usb core. And the USB core
> 
> DMA
> USB

Okay.

Thanks,
Xu Yang

> 
> > layer will manage synchronization itself.
> 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
>