[PATCH] mmc: dw_mmc: fix card read threshold for PIO mode

Shawn Guo shawn.guo at linaro.org
Thu Nov 20 22:39:10 PST 2014

Commit f1d2736c8156 ("mmc: dw_mmc: control card read threshold")
introduces a regression for use case where PIO mode is used, i.e.
CONFIG_MMC_DW_IDMAC is not disabled.  It stops kernel from booting
like below.

dw_mmc 9408000.dwmmc: fifo-depth property not found, using value of FIFOTH register as default
dw_mmc 9408000.dwmmc: Using PIO mode.
dw_mmc 9408000.dwmmc: Version ID is 210a
dw_mmc 9408000.dwmmc: DW MMC controller at irq 72, 32 bit host data width, 32 deep fifo
dw_mmc 9408000.dwmmc: 1 slots initialized
Waiting for root device /dev/mmcblk0p2...
mmc_host mmc0: Bus speed (slot 0) = 52000000Hz (slot req 50000000Hz, actual 26000000HZ div = 1)
mmc0: new high speed SDHC card at address b368
mmcblk0: mmc0:b368 AF UD 3.84 GiB

Rather than clearing read threshold bits, the best thing that function
dw_mci_ctrl_rd_thld() should do is leaving the bits untouched, in case
that card read threshold setup is not needed.

The patch fixes the regression by changing dw_mci_ctrl_rd_thld() a bit
to do nothing in case card read threshold bits setup is not needed.

Signed-off-by: Shawn Guo <shawn.guo at linaro.org>
Fixes: f1d2736c8156 ("mmc: dw_mmc: control card read threshold")
Cc: <stable at vger.kernel.org> # 3.13+
 drivers/mmc/host/dw_mmc.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 69f0cc68d5b2..52c04ba69970 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -628,13 +628,13 @@ static void dw_mci_ctrl_rd_thld(struct dw_mci *host, struct mmc_data *data)
 	if (host->timing != MMC_TIMING_MMC_HS200 &&
 	    host->timing != MMC_TIMING_UHS_SDR104)
-		goto disable;
+		return;
 	blksz_depth = blksz / (1 << host->data_shift);
 	fifo_depth = host->fifo_depth;
 	if (blksz_depth > fifo_depth)
-		goto disable;
+		return;
 	 * If (blksz_depth) >= (fifo_depth >> 1), should be 'thld_size <= blksz'
@@ -644,9 +644,6 @@ static void dw_mci_ctrl_rd_thld(struct dw_mci *host, struct mmc_data *data)
 	thld_size = blksz;
 	mci_writel(host, CDTHRCTL, SDMMC_SET_RD_THLD(thld_size, 1));
-	mci_writel(host, CDTHRCTL, SDMMC_SET_RD_THLD(0, 0));
 static int dw_mci_submit_data_dma(struct dw_mci *host, struct mmc_data *data)

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