[PATCH v4 20/25] mmc: sdhci: further fix for DMA unmapping in sdhci_post_req()

Russell King
2016-01-29T09:50:30Z

sdhci_post_req() exists to unmap a previously mapped but already
finished request, while the next request is in progress. However, the
state of the SDHCI_REQ_USE_DMA flag depends on the last submitted
request.

This means we can end up clearing the flag due to a quirk, which then
means that sdhci_post_req() fails to unmap the DMA buffer, potentially
leading to data corruption.

We can safely ignore the SDHCI_REQ_USE_DMA here, as testing
data->host_cookie is entirely sufficient.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
drivers/mmc/host/sdhci.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index b4808ca8e497..7fed845797a0 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -2059,13 +2059,12 @@ static void sdhci_post_req(struct mmc_host *mmc, struct mmc_request *mrq,
struct sdhci_host *host = mmc_priv(mmc);
struct mmc_data *data = mrq->data;

- if (host->flags & SDHCI_REQ_USE_DMA) {
- if (data->host_cookie != COOKIE_UNMAPPED)
- dma_unmap_sg(mmc_dev(host->mmc), data->sg, data->sg_len,
- data->flags & MMC_DATA_WRITE ?
- DMA_TO_DEVICE : DMA_FROM_DEVICE);
- data->host_cookie = COOKIE_UNMAPPED;
- }
+ if (data->host_cookie != COOKIE_UNMAPPED)
+ dma_unmap_sg(mmc_dev(host->mmc), data->sg, data->sg_len,
+ data->flags & MMC_DATA_WRITE ?
+ DMA_TO_DEVICE : DMA_FROM_DEVICE);
+
+ data->host_cookie = COOKIE_UNMAPPED;
}

static void sdhci_pre_req(struct mmc_host *mmc, struct mmc_request *mrq,
--
2.1.0