Re: [PATCH] mmc: mxcmmc: fix bug that may block a data transfer forever.

[Sascha Hauer <s.hauer@pengutronix.de>]

On Thu, Sep 06, 2012 at 09:40:48AM +0200, Javier Martin wrote:
> The problem can be easily reproduced using a script that loops
> copying a file in an SD card to another place in the same SD card
> and its related to read transfers. This only happens with DMA enabled.
> 
> This is related to the fact that, when reading, an MMC irq signals
> the fact that all data from the SD card has been copied to the
> internal buffers. However, it doesn't signal whether the DMA transfer
> that is in charge of moving data from these internal buffers to RAM
> has finished or not. Thus, calling dmaengine_terminate_all() in the
> MMC irq routine can cancel an ongoing DMA transfer leaving some data
> in the internal buffers that produces an accumulative effect which,
> in the end, blocks a read data transfer forever.

Doesn't that mean that in case of a DMA read we just have to wait for
the DMA callback instead of the MMC irq? Something like:

static int mxcmci_start_cmd(struct mxcmci_host *host, struct mmc_command *cmd,
		unsigned int cmdat)
{
	...

	if (mxcmci_use_dma(host)) {
		if (host->dma_dir == DMA_FROM_DEVICE)
			setup_dma_callback();
		else
			int_cntr |= INT_WRITE_OP_DONE_EN;
	}

	...
}

That would be a cleaner solution I think.

Sascha

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