[PATCH] spi: pxa2xx: Set controller->max_transfer_size in dma mode

[Andy Shevchenko]

On Thu, Oct 17, 2019 at 10:06:38AM +0300, Andy Shevchenko wrote:
> On Thu, Oct 17, 2019 at 08:44:26AM +0200, Daniel Vetter wrote:
> > In DMA mode we have a maximum transfer size, past that the driver
> > falls back to PIO (see the check at the top of pxa2xx_spi_transfer_one).
> > Falling back to PIO for big transfers defeats the point of a dma engine,
> > hence set the max transfer size to inform spi clients that they need
> > to do something smarter.
> > 
> > This was uncovered by the drm_mipi_dbi spi panel code, which does
> > large spi transfers, but stopped splitting them after:
> > 
> > commit e143364b4c1774f68e923a5a0bb0fca28ac25888
> > Author: Noralf Trønnes <noralf at tronnes.org>
> > Date:   Fri Jul 19 17:59:10 2019 +0200
> > 
> >     drm/tinydrm: Remove tinydrm_spi_max_transfer_size()
> > 
> > After this commit the code relied on the spi core to split transfers
> > into max dma-able blocks, which also papered over the PIO fallback issue.
> > 
> > Fix this by setting the overall max transfer size to the DMA limit,
> > but only when the controller runs in DMA mode.
> > 
> 
> Thank you, Daniel!

Mark, can be this applied?

-- 
With Best Regards,
Andy Shevchenko