mmc: sdhci: 8-bit bus width changes

We now:
 * check for a v3 controller before setting 8-bit bus width
 * offer a callback for platform code to switch to 8-bit mode, which
   allows non-v3 controllers to support it
 * rely on mmc->caps |= MMC_CAP_8_BIT_DATA; in platform code to specify
   that the board designers have indeed brought out all the pins for
   8-bit to the slot.

We were previously relying only on whether the *controller* supported
8-bit, which doesn't tell us anything about the pin configuration in
the board design.

This fixes the MMC card regression reported by Maxim Levitsky here:
   http://thread.gmane.org/gmane.linux.kernel.mmc/4336
by no longer assuming that 8-bit works by default.
Signed-off-by: Philip Rakity <prakity@marvell.com>
Tested-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

arch/arm/plat-pxa/include/plat/sdhci.h

@@ -17,6 +17,9 @@
 /* Require clock free running */
 #define PXA_FLAG_DISABLE_CLOCK_GATING (1<<0)
 
+/* Board design supports 8-bit data on SD/SDIO BUS */
+#define PXA_FLAG_SD_8_BIT_CAPABLE_SLOT (1<<2)
+
 /*
  * struct pxa_sdhci_platdata() - Platform device data for PXA SDHCI
  * @max_speed: the maximum speed supported

drivers/mmc/host/sdhci-pxa.c

@@ -141,6 +141,10 @@ static int __devinit sdhci_pxa_probe(struct platform_device *pdev)
 	if (pdata->quirks)
 		host->quirks |= pdata->quirks;
 
+	/* If slot design supports 8 bit data, indicate this to MMC. */
+	if (pdata->flags & PXA_FLAG_SD_8_BIT_CAPABLE_SLOT)
+		host->mmc->caps |= MMC_CAP_8_BIT_DATA;
+
 	ret = sdhci_add_host(host);
 	if (ret) {
 		dev_err(&pdev->dev, "failed to add host\n");

drivers/mmc/host/sdhci.c

@@ -1185,17 +1185,31 @@ static void sdhci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 	if (host->ops->platform_send_init_74_clocks)
 		host->ops->platform_send_init_74_clocks(host, ios->power_mode);
 
+	/*
+	 * If your platform has 8-bit width support but is not a v3 controller,
+	 * or if it requires special setup code, you should implement that in
+	 * platform_8bit_width().
+	 */
+	if (host->ops->platform_8bit_width)
+		host->ops->platform_8bit_width(host, ios->bus_width);
+	else {
 		ctrl = sdhci_readb(host, SDHCI_HOST_CONTROL);
-
-	if (ios->bus_width == MMC_BUS_WIDTH_8)
+		if (ios->bus_width == MMC_BUS_WIDTH_8) {
+			ctrl &= ~SDHCI_CTRL_4BITBUS;
+			if (host->version >= SDHCI_SPEC_300)
 				ctrl |= SDHCI_CTRL_8BITBUS;
-	else
+		} else {
+			if (host->version >= SDHCI_SPEC_300)
 				ctrl &= ~SDHCI_CTRL_8BITBUS;
-
 			if (ios->bus_width == MMC_BUS_WIDTH_4)
 				ctrl |= SDHCI_CTRL_4BITBUS;
 			else
 				ctrl &= ~SDHCI_CTRL_4BITBUS;
+		}
+		sdhci_writeb(host, ctrl, SDHCI_HOST_CONTROL);
+	}
+
+	ctrl = sdhci_readb(host, SDHCI_HOST_CONTROL);
 
 	if ((ios->timing == MMC_TIMING_SD_HS ||
 	     ios->timing == MMC_TIMING_MMC_HS)
@@ -1855,11 +1869,19 @@ int sdhci_add_host(struct sdhci_host *host)
 		mmc->f_min = host->max_clk / SDHCI_MAX_DIV_SPEC_300;
 	else
 		mmc->f_min = host->max_clk / SDHCI_MAX_DIV_SPEC_200;
+
 	mmc->f_max = host->max_clk;
 	mmc->caps |= MMC_CAP_SDIO_IRQ;
 
+	/*
+	 * A controller may support 8-bit width, but the board itself
+	 * might not have the pins brought out.  Boards that support
+	 * 8-bit width must set "mmc->caps |= MMC_CAP_8_BIT_DATA;" in
+	 * their platform code before calling sdhci_add_host(), and we
+	 * won't assume 8-bit width for hosts without that CAP.
+	 */
 	if (!(host->quirks & SDHCI_QUIRK_FORCE_1_BIT_DATA))
-		mmc->caps |= MMC_CAP_4_BIT_DATA | MMC_CAP_8_BIT_DATA;
+		mmc->caps |= MMC_CAP_4_BIT_DATA;
 
 	if (caps & SDHCI_CAN_DO_HISPD)
 		mmc->caps |= MMC_CAP_SD_HIGHSPEED | MMC_CAP_MMC_HIGHSPEED;

drivers/mmc/host/sdhci.h

@@ -155,6 +155,7 @@
 #define  SDHCI_CLOCK_BASE_SHIFT	8
 #define  SDHCI_MAX_BLOCK_MASK	0x00030000
 #define  SDHCI_MAX_BLOCK_SHIFT  16
+#define  SDHCI_CAN_DO_8BIT	0x00040000
 #define  SDHCI_CAN_DO_ADMA2	0x00080000
 #define  SDHCI_CAN_DO_ADMA1	0x00100000
 #define  SDHCI_CAN_DO_HISPD	0x00200000
@@ -215,6 +216,8 @@ struct sdhci_ops {
 	unsigned int	(*get_max_clock)(struct sdhci_host *host);
 	unsigned int	(*get_min_clock)(struct sdhci_host *host);
 	unsigned int	(*get_timeout_clock)(struct sdhci_host *host);
+	int		(*platform_8bit_width)(struct sdhci_host *host,
+					       int width);
 	void (*platform_send_init_74_clocks)(struct sdhci_host *host,
 					     u8 power_mode);
 	unsigned int    (*get_ro)(struct sdhci_host *host);