[PATCH 1/1] mmc: host: enable OMAP DMA engine support for omap hosts by default

Shilimkar, Santosh santosh.shilimkar at ti.com
Wed Jul 18 04:36:45 EDT 2012


On Wed, Jul 18, 2012 at 1:14 PM, S, Venkatraman <svenkatr at ti.com> wrote:
> On Wed, Jul 18, 2012 at 12:40 PM, Tony Lindgren <tony at atomide.com> wrote:
>> * Shilimkar, Santosh <santosh.shilimkar at ti.com> [120718 00:09]:
>>> On Wed, Jul 18, 2012 at 12:29 PM, Tony Lindgren <tony at atomide.com> wrote:
>>> > * Javier Martinez Canillas <javier at dowhile0.org> [120716 23:56]:
>>> >> On Tue, Jul 17, 2012 at 8:45 AM, Shilimkar, Santosh
>>> >> <santosh.shilimkar at ti.com> wrote:
>>> >> > Hi,
>>> >> >
>>> >> > On Tue, Jul 17, 2012 at 6:00 AM, Javier Martinez Canillas
>>> >> > <javier at dowhile0.org> wrote:
>>> >> >> The OMAP MMC and OMAP High Speed MMC hosts now use entirely the DMA
>>> >> >> engine API instead of the previous private DMA API implementation.
>>> >> >>
>>> >> >> So, if the kernel is built with support for any of these hosts but it
>>> >> >> doesn't support DMA devices nor OMAP DMA support, it fails when trying
>>> >> >> to obtain a DMA channel which leads to the following error on an OMAP3
>>> >> >> IGEPv2 Rev.C board (and probably on most OMAP boards with MMC support):
>>> >> >>
>>> >> >> [    2.199981] omap_hsmmc omap_hsmmc.1: unable to obtain RX DMA engine channel 48
>>> >> >> [    2.215087] omap_hsmmc omap_hsmmc.0: unable to obtain RX DMA engine channel 62
>>> >> >>
>>> >> >> selecting automatically CONFIG_DMADEVICES and CONFIG_DMA_OMAP solves it.
>>> >> >>
>>> >> >> Signed-off-by: Javier Martinez Canillas <javier at dowhile0.org>
>>> >> >> ---
>>> >> > Considering, we are updating drivers to select the DMA engine, can you
>>> >> > also include
>>> >> > "drivers/spi/spi-omap2-mcspi.c" which is also updated for DMA engine.
>>> >> >
>>> >> > Regards
>>> >> > Santosh
>>> >>
>>> >> Hi Santosh,
>>> >>
>>> >> Ok, I'll send a v2 now which includes spi-omap2-mcspi then.
>>> >
>>> > I don't think we should do this, the drivers should work with and without
>>> > dma. This just needs to be added to the omap2plus_defconfig.
>>> >
>>> Well this was not decided based on any DMA CONFIG option before for
>>> the subject drivers. It is already by default enabled if the DMA is supported
>>> by the driver IP. There is a possibility to disable it from driver platform/dt
>>> data so that still remains.
>>
>> I think it should rather be that if the driver is broken and does not work
>> without DMA, it should have depends on CONFIG_DMA_OMAP.
>>
> I can confirm that omap MMC can't work without DMA; polled mode is not
> supported / implemented.

Same case for SPI driver as well. It uses DMA for everything except the cases
where DMA doesn't make sense like 1 byte/2 byte etc. And its not configurable,

At least considering this, it is better we do this per driver than enabling
it at SOC config.

Regards
Santosh



More information about the linux-arm-kernel mailing list