Re: [PATCH AUTOSEL 5.4 128/350] spi: pxa2xx: Set controller->max_transfer_size in dma mode

On Tue, Dec 10, 2019 at 04:03:53PM -0500, Sasha Levin wrote:

From: Daniel Vetter daniel.vetter@ffwll.ch

[ Upstream commit b2662a164f9dc48da8822e56600686d639056282 ]

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 won't fix anything by itself, this asks other code to change how it behaves which may or may not work in older kernels.