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

From: Joel A Fernandes
Date: Fri Jun 21 2013 - 22:53:46 EST

>> > config TI_EDMA
>> > tristate "TI EDMA support"
>> > default m if 'ARCH_DAVINCI || ARCH_OMAP1 || ARCH_OMAP2
>> > select DMA_ENGINE
>> 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 *);
static inline bool edma_filter_fn(struct dma_chan *chan, void *param)
return false;

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

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