-
Linus Walleij authored
commit 64b12a68 "mmc: core: fix prepared requests while doing bkops" is fixing a bug in the wrong way. A bug in the MMCI device driver is fixed by amending the MMC core. Thinking about it: what the pre- and post-callbacks are doing is to essentially map and unmap SG lists for DMA transfers. Why would we not be able to do that just because a BKOPS command is sent inbetween? Having to unprepare/prepare the next asynchronous request for DMA seems wrong. Looking the backtrace in that commit we can see what the real problem actually is: mmci_data_irq() is calling mmci_dma_unmap() twice which is goung to call arm_dma_unmap_sg() twice and v7_dma_inv_range() twice for the same sglist and that will crash. This happens because a request is prepared, then a BKOPS is sent. The IRQ completing the BKOPS command goes through mmci_data_irq() and thinks that a DMA operation has just been completed because dma_inprogress() reports true. It then proceeds to unmap the sglist. But that was wrong! dma_inprogress() should NOT be true because no DMA was actually in progress! We had just prepared the sglist, and the DMA channel dma_current has been configured, but NOT started! Because of this, the sglist is already unmapped when we get our actual data completion IRQ, and we are unmapping the sglist once more, and we get this crash. Therefore, we need to revert this solution pushing the problem to the core and causing problems, and instead augment the implementation such that dma_inprogress() only reports true if some DMA has actually been started. After this we can keep the request prepared during the BKOPS and we need not unprepare/reprepare it. Fixes: 64b12a68 ("mmc: core: fix prepared requests while doing bkops") Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> Signed-off-by:
Linus Walleij <linus.walleij@linaro.org> Tested-by:
Srinivas Kandagatla <srinivas.kandagatla@linaro.org> Signed-off-by:
Ulf Hansson <ulf.hansson@linaro.org>
e13934bd