mmc: esdhc-imx: fix card interrupt loss on freescale eSDHC

Apply a workaround for the imx eSDHC controller to avoid missing
card interrupts.  This makes SDIO work.
Signed-off-by: Tony Lin <tony.lin@freescale.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/host/sdhci-esdhc-imx.c

@@ -27,6 +27,7 @@
 #include "sdhci-pltfm.h"
 #include "sdhci-esdhc.h"
 
+#define	SDHCI_CTRL_D3CD			0x08
 /* VENDOR SPEC register */
 #define SDHCI_VENDOR_SPEC		0xC0
 #define  SDHCI_VENDOR_SPEC_SDIO_QUIRK	0x00000002
@@ -141,14 +142,33 @@ static void esdhc_writel_le(struct sdhci_host *host, u32 val, int reg)
 	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
 	struct pltfm_imx_data *imx_data = pltfm_host->priv;
 	struct esdhc_platform_data *boarddata = &imx_data->boarddata;
+	u32 data;
 
-	if (unlikely((reg == SDHCI_INT_ENABLE || reg == SDHCI_SIGNAL_ENABLE)
-			&& (boarddata->cd_type == ESDHC_CD_GPIO)))
+	if (unlikely(reg == SDHCI_INT_ENABLE || reg == SDHCI_SIGNAL_ENABLE)) {
+		if (boarddata->cd_type == ESDHC_CD_GPIO)
 			/*
-		 * these interrupts won't work with a custom card_detect gpio
+			 * These interrupts won't work with a custom
+			 * card_detect gpio (only applied to mx25/35)
 			 */
 			val &= ~(SDHCI_INT_CARD_REMOVE | SDHCI_INT_CARD_INSERT);
 
+		if (val & SDHCI_INT_CARD_INT) {
+			/*
+			 * Clear and then set D3CD bit to avoid missing the
+			 * card interrupt.  This is a eSDHC controller problem
+			 * so we need to apply the following workaround: clear
+			 * and set D3CD bit will make eSDHC re-sample the card
+			 * interrupt. In case a card interrupt was lost,
+			 * re-sample it by the following steps.
+			 */
+			data = readl(host->ioaddr + SDHCI_HOST_CONTROL);
+			data &= ~SDHCI_CTRL_D3CD;
+			writel(data, host->ioaddr + SDHCI_HOST_CONTROL);
+			data |= SDHCI_CTRL_D3CD;
+			writel(data, host->ioaddr + SDHCI_HOST_CONTROL);
+		}
+	}
+
 	if (unlikely((imx_data->flags & ESDHC_FLAG_MULTIBLK_NO_INT)
 				&& (reg == SDHCI_INT_STATUS)
 				&& (val & SDHCI_INT_DATA_END))) {
@@ -217,8 +237,10 @@ static void esdhc_writeb_le(struct sdhci_host *host, u8 val, int reg)
 		 */
 		return;
 	case SDHCI_HOST_CONTROL:
-		/* FSL messed up here, so we can just keep those two */
-		new_val = val & (SDHCI_CTRL_LED | SDHCI_CTRL_4BITBUS);
+		/* FSL messed up here, so we can just keep those three */
+		new_val = val & (SDHCI_CTRL_LED | \
+				SDHCI_CTRL_4BITBUS | \
+				SDHCI_CTRL_D3CD);
 		/* ensure the endianess */
 		new_val |= ESDHC_HOST_CONTROL_LE;
 		/* DMA mode bits are shifted */