[PATCH v2 2/2] mmc: dw_mmc: check card present before starting request

From: Shawn Lin
Date: Fri May 27 2016 - 02:37:34 EST

The main reason to add this check is to avoid unnecessary
mmc_request like the on-going cmd and the corresponding sbc
if the card is removed. Although we have already checked this in
dw_mci_handle_cd for runtime usage of sd card and dw_mci_init_slot
for noremovable devices, but there is a timing gap before it really
calls dw_mci_get_cd as mmc_detect_change needs some delay here.

Another gain here is that we could save some checkings of card status
after sd card been removed.

Signed-off-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>


Changes in v2:
- hold lock before dw_mci_queue_request

drivers/mmc/host/dw_mmc.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index cb30e91..2b4b3df 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -105,6 +105,7 @@ struct idmac_desc {
static bool dw_mci_reset(struct dw_mci *host);
static bool dw_mci_ctrl_reset(struct dw_mci *host, u32 reset);
static int dw_mci_card_busy(struct mmc_host *mmc);
+static int dw_mci_get_cd(struct mmc_host *mmc);

#if defined(CONFIG_DEBUG_FS)
static int dw_mci_req_show(struct seq_file *s, void *v)
@@ -1253,15 +1254,15 @@ static void dw_mci_request(struct mmc_host *mmc, struct mmc_request *mrq)
* atomic, otherwise the card could be removed in between and the
* request wouldn't fail until another card was inserted.
- spin_lock_bh(&host->lock);

- if (!test_bit(DW_MMC_CARD_PRESENT, &slot->flags)) {
- spin_unlock_bh(&host->lock);
+ if (!dw_mci_get_cd(mmc)) {
mrq->cmd->error = -ENOMEDIUM;
mmc_request_done(mmc, mrq);

+ spin_lock_bh(&host->lock);
dw_mci_queue_request(host, slot, mrq);