Re: [PATCH 00/11] of: dma-ranges fixes and improvements

[Christoph Hellwig]

On Sun, Sep 29, 2019 at 01:16:20PM +0200, Arnd Bergmann wrote:
> On a semi-related note, Thierry asked about one aspect of the dma-ranges
> property recently, which is the behavior of dma_set_mask() and related
> functions when a driver sets a mask that is larger than the memory
> area in the bus-ranges but smaller than the available physical RAM.
> As I understood Thierry's problem and the current code, the generic
> dma_set_mask() will either reject the new mask entirely or override
> the mask set by of_dma_configure, but it fails to set a correct mask
> within the limitations of the parent bus in this case.

There days dma_set_mask will only reject a mask if it is too small
to be supported by the hardware.  Larger than required masks are now
always accepted.