[PATCH v3 1/3] mmc:sdhci: Add a quirk for AMD SDHC transfer mode register need to be cleared for cmd without data

[Vincent Wan <vincent.wan@amd.com>]

SDHC controller in AMD chipsets require SDHC transfer mode
register to be cleared for commands without data. The issue was
uncovered during testing eMMC cards on KB/ML based platforms

Signed-off-by: Vincent Wan <vincent.wan@amd.com>
Signed-off-by: Wan Zongshun <mcuos.com@gmail.com>
Signed-off-by: Arindam Nath <arindam.nath@amd.com>
Tested-by: Vikram B <vikram.b@amd.com>
Tested-by: Raghavendra Swamy <raghavendra.swamy@amd.com>
---
 drivers/mmc/host/sdhci.c  | 9 +++++++--
 include/linux/mmc/sdhci.h | 2 ++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index f895ab0..a743d52 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -915,10 +915,15 @@ static void sdhci_set_transfer_mode(struct sdhci_host *host,
 	struct mmc_data *data = cmd->data;
 
 	if (data == NULL) {
+		if (host->quirks2 &
+			SDHCI_QUIRK2_CLEAR_TRANSFERMODE_REG_BEFORE_CMD) {
+			sdhci_writew(host, 0x0, SDHCI_TRANSFER_MODE);
+		} else {
 		/* clear Auto CMD settings for no data CMDs */
-		mode = sdhci_readw(host, SDHCI_TRANSFER_MODE);
-		sdhci_writew(host, mode & ~(SDHCI_TRNS_AUTO_CMD12 |
+			mode = sdhci_readw(host, SDHCI_TRANSFER_MODE);
+			sdhci_writew(host, mode & ~(SDHCI_TRNS_AUTO_CMD12 |
 				SDHCI_TRNS_AUTO_CMD23), SDHCI_TRANSFER_MODE);
+		}
 		return;
 	}
 
diff --git a/include/linux/mmc/sdhci.h b/include/linux/mmc/sdhci.h
index 931ac5e..ae7f357 100644
--- a/include/linux/mmc/sdhci.h
+++ b/include/linux/mmc/sdhci.h
@@ -102,6 +102,8 @@ struct sdhci_host {
 #define SDHCI_QUIRK2_STOP_WITH_TC			(1<<8)
 /* Controller does not support 64-bit DMA */
 #define SDHCI_QUIRK2_BROKEN_64_BIT_DMA			(1<<9)
+/* need clear transfer mode register before send cmd */
+#define SDHCI_QUIRK2_CLEAR_TRANSFERMODE_REG_BEFORE_CMD	(1<<10)
 
 	int irq;		/* Device IRQ */
 	void __iomem *ioaddr;	/* Mapped address */
-- 
1.8.1.2