[PATCH v4 17/25] mmc: sdhci: clean up host cookie handling

Russell King
2016-01-29T09:50:13Z

Commit d31911b9374a ("mmc: sdhci: fix dma memory leak in sdhci_pre_req()")
added a complicated method to manage the DMA map state for the data
transfer, but this complexity is not required.

There are three states:
* Unmapped
* Mapped by sdhci_pre_req()
* Mapped by sdhci_prepare_data()

sdhci_prepare_data() needs to know when the data buffers have been
successfully mapped by sdhci_pre_req(), and if so, there is no need to
map them a second time.

When we come to tear down the mapping, we want to know whether
sdhci_post_req() will be called (which is determined by sdhci_pre_req()
having been previously called) so that we can postpone the unmap
operation.

Hence, it makes sense to simply record when the successful DMA map
happened (via COOKIE_PRE_MAPPED vs COOKIE_MAPPED) rather than having
the complex mechanics involving COOKIE_MAPPED vs COOKIE_GIVEN.

If a mapping is created by sdhci_prepare_data(), we must tear it down
ourselves, without waiting for sdhci_post_req() (hence, the new
COOKIE_MAPPED case). If the mapping is created by sdhci_pre_req()
then sdhci_post_req() is responsible for tearing the mapping down.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
drivers/mmc/host/sdhci.c | 12 ++++++------
drivers/mmc/host/sdhci.h | 4 ++--
2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 3da2a0461e4b..a714c628394b 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -431,12 +431,12 @@ static int sdhci_pre_dma_transfer(struct sdhci_host *host,
{
int sg_count;

- if (data->host_cookie == COOKIE_MAPPED) {
- data->host_cookie = COOKIE_GIVEN;
+ /*
+ * If the data buffers are already mapped, return the previous
+ * dma_map_sg() result.
+ */
+ if (data->host_cookie == COOKIE_PRE_MAPPED)
return data->sg_count;
- }
-
- WARN_ON(data->host_cookie == COOKIE_GIVEN);

sg_count = dma_map_sg(mmc_dev(host->mmc), data->sg, data->sg_len,
data->flags & MMC_DATA_WRITE ?
@@ -2084,7 +2084,7 @@ static void sdhci_pre_req(struct mmc_host *mmc, struct mmc_request *mrq,
mrq->data->host_cookie = COOKIE_UNMAPPED;

if (host->flags & SDHCI_REQ_USE_DMA)
- sdhci_pre_dma_transfer(host, mrq->data, COOKIE_MAPPED);
+ sdhci_pre_dma_transfer(host, mrq->data, COOKIE_PRE_MAPPED);
}

static void sdhci_card_event(struct mmc_host *mmc)
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index 7654ae5d2b4e..19e9291e5074 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -316,8 +316,8 @@ struct sdhci_adma2_64_desc {

enum sdhci_cookie {
COOKIE_UNMAPPED,
- COOKIE_MAPPED,
- COOKIE_GIVEN,
+ COOKIE_PRE_MAPPED, /* mapped by sdhci_pre_req() */
+ COOKIE_MAPPED, /* mapped by sdhci_prepare_data() */
};

struct sdhci_host {
--
2.1.0