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

[Shilimkar, Santosh]

On Wed, Jul 18, 2012 at 2:19 PM, Javier Martinez Canillas
<martinez.javier at gmail.com> wrote:
> On Wed, Jul 18, 2012 at 10:36 AM, Shilimkar, Santosh
> <santosh.shilimkar at ti.com> wrote:
>> 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
>> --
>
> Hi Santosh,
>
> And what about enabling it at the SoC config level but making the
> drivers dependant on CONFIG_DMADEVICES and CONFIG_DMA_OMAP? If you
> agree I can send something like this in two different patches (one for
> the omap2plus_defconfig and another to make the drivers dependant on
> the config option):
>
> diff --git a/arch/arm/configs/omap2plus_defconfig
> b/arch/arm/configs/omap2plus_defconfig
> index b152de7..e58edc3 100644
> --- a/arch/arm/configs/omap2plus_defconfig
> +++ b/arch/arm/configs/omap2plus_defconfig
> @@ -193,6 +193,8 @@ CONFIG_MMC_OMAP_HS=y
>  CONFIG_RTC_CLASS=y
>  CONFIG_RTC_DRV_TWL92330=y
>  CONFIG_RTC_DRV_TWL4030=y
> +CONFIG_DMADEVICES=y
> +CONFIG_DMA_OMAP=y
>  CONFIG_EXT2_FS=y
>  CONFIG_EXT3_FS=y
>  # CONFIG_EXT3_FS_XATTR is not set
> diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
> index aa131b3..314c7bd 100644
> --- a/drivers/mmc/host/Kconfig
> +++ b/drivers/mmc/host/Kconfig
> @@ -231,7 +231,7 @@ config MMC_SDHCI_S3C_DMA
>
>  config MMC_OMAP
>         tristate "TI OMAP Multimedia Card Interface support"
> -       depends on ARCH_OMAP
> +       depends on ARCH_OMAP && DMADEVICES && DMA_OMAP

May be. But since for sure a driver knows that it needs DMA
support to be enabled, I will just select it rather than depends
on.

Regards
santosh