Re: [PATCH/RFC 5/5] mmc: renesas-sdhi: remove gen3 support from sysc dmac driver

Magnus Damm
2017-06-09T08:40:17Z

Hi Geert and Simon,

On Fri, Jun 9, 2017 at 4:40 PM, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> Hi Simon,
>
> On Thu, Jun 8, 2017 at 3:09 PM, Simon Horman <horms+renesas@verge.net.au> wrote:
>> Gen3 SoCs are now supported by the internal dmac variant of the SDHI driver.
>> Remove them from the sys dmac variant where only PIO mode is supported.
>>
>> Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
>
> Is it possible to fall back to PIO with the new DMAC driver?
> If not, is this desirable?

I believe R-Car Gen3 SDHI may depending on SoC use either on-chip bus
mastering DMA or SYS-DMAC via DMA Engine. In both cases fall back to
PIO is most likely valid. For any given SoC which is better of on-chip
DMA or SYS-DMAC needs to be investigated together with IPMMU.

Cheers,

/ magnus