Re: [PATCH 3/3] dw_mmc: Handle unaligned data submission correctly

From: Chris Ball
Date: Fri Mar 22 2013 - 12:52:20 EST


On Tue, Mar 12 2013, Markos Chandras wrote:
> Commit f9c2a0dc42a6938ff2a80e55ca2bbd1d5581c72e
> "mmc: dw_mmc: Fix PIO mode with support of highmem" introduced
> a regression since v3.2 making the mmc_test hang on test #13
> with a "Data starvation by host timeout" interrupt.
> This is because, sg_mapping_iter is used to iterate through the
> data which spans on multiple pages. The problem is detected on
> unaligned data submission where the code previously checked for
> !(sg_next(host->sg)) which is true because we only have a single
> scatter/gather list which then expands to multiple pages.
> Therefore, the driver incorrectly assumed that this was the last
> list item and submitted unaligned data to the mmc device. This
> overflowed the FIFO on the device before all the data were written
> to it. The code was fixed to only submit unaligned data when we are
> handling the last sg_miter item by checking whether we reached
> the desired data length or not.
> The patch was tested against mmc_test and all the tests passed.
> Signed-off-by: Markos Chandras <markos.chandras@xxxxxxxxxx>
> Cc: Seungwon Jeon <tgih.jun@xxxxxxxxxxx>
> Cc: Jaehoon Chung <jh80.chung@xxxxxxxxxxx>
> Cc: Chris Ball <cjb@xxxxxxxxxx>

Thanks, pushed to mmc-next for 3.10.

- Chris.
Chris Ball <cjb@xxxxxxxxxx> <>
One Laptop Per Child
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