Re: [PATCH v12 05/11] edma: config: Enable config options for EDMA

[Joel A Fernandes <agnel.joel-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On Mon, Jun 24, 2013 at 6:53 AM, Sekhar Nori <nsekhar-l0cyMroinI0@public.gmane.org> wrote:
> On 6/22/2013 8:23 AM, Joel A Fernandes wrote:
>>>>> config TI_EDMA
>>>>>         tristate "TI EDMA support"
>>>>>         default m if 'ARCH_DAVINCI || ARCH_OMAP1 || ARCH_OMAP2
>>>>>         select DMA_ENGINE
>>>>>         select DMA_VIRTUAL_CHANNELS
>>>>
>>>>
>>>> MMC depends on EDMA specially on AM33xx there's no PIO mode AFAIK. The
>>>> 'm' option will require some initramfs to load the module when needing
>>>> to MMC boot, I suggest lets leave it as y.
>>>>
>>>
>>> Ah, right: you still export a filter function from the edma driver
>>> and use it in slave drivers:
>>>
>>> drivers/mmc/host/davinci_mmc.c:         dma_request_slave_channel_compat(mask, edma_filter_fn,
>>> drivers/mmc/host/davinci_mmc.c:         dma_request_slave_channel_compat(mask, edma_filter_fn,
>>> drivers/spi/spi-davinci.c:      dspi->dma_rx = dma_request_channel(mask, edma_filter_fn,
>>> drivers/spi/spi-davinci.c:      dspi->dma_tx = dma_request_channel(mask, edma_filter_fn,
>>>
>>> As long as this is the case, you have to be careful with the dependencies
>>> to make sure that davinci_mmc and spi-davinci either depend on TI_EDMA, or
>>> edma_filter_fn gets defined to NULL when you are building for a DT-only platform.
>>
>> Yes sure, right now they are defined  as follows in include/linux/edma.h:
>>
>> #if defined(CONFIG_TI_EDMA) || defined(CONFIG_TI_EDMA_MODULE)
>> bool edma_filter_fn(struct dma_chan *, void *);
>> #else
>> static inline bool edma_filter_fn(struct dma_chan *chan, void *param)
>> {
>> return false;
>> }
>> #endif
>>
>> This also has the side effect of causing DMA requests to fail if
>> TI_EDMA is not built, causing frustration for a lot of people some of
>> whom don't want to deal with DMA so I think it is OK to build the
>> driver in by default as it is (and will be) used by a lot of
>> OMAP2PLUS.
>
> Solution for this is to enable TI_EDMA in relevant defconfigs. Most
> folks who would get frustrated by such issues would be using defconfigs
> and for those who are building their configuration from scratch this
> will be pretty low in their list of worries.

Yes, it is not in omap2plus_defconfig either. I will post a patch to
add it to the same, and we can ignore the Kconfig defaults and select
patches.

Thanks,
Joel

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