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

[Javier Martinez Canillas]

On Wed, Jul 18, 2012 at 11:11 AM, Shilimkar, Santosh
<santosh.shilimkar at ti.com> wrote:
> 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

Yes I agree with you, I was just exploring other options :-)

Best regards,
Javier