mmc: sdhci: Add sd host v4 mode

For SD host controller version 4.00 or later ones, there're two
modes of implementation - Version 3.00 compatible mode or
Version 4 mode.  This patch introduced an interface to enable
v4 mode.
Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci.c

@@ -123,6 +123,29 @@ EXPORT_SYMBOL_GPL(sdhci_dumpregs);
  *                                                                           *
 \*****************************************************************************/
 
+static void sdhci_do_enable_v4_mode(struct sdhci_host *host)
+{
+	u16 ctrl2;
+
+	ctrl2 = sdhci_readb(host, SDHCI_HOST_CONTROL2);
+	if (ctrl2 & SDHCI_CTRL_V4_MODE)
+		return;
+
+	ctrl2 |= SDHCI_CTRL_V4_MODE;
+	sdhci_writeb(host, ctrl2, SDHCI_HOST_CONTROL);
+}
+
+/*
+ * This can be called before sdhci_add_host() by Vendor's host controller
+ * driver to enable v4 mode if supported.
+ */
+void sdhci_enable_v4_mode(struct sdhci_host *host)
+{
+	host->v4_mode = true;
+	sdhci_do_enable_v4_mode(host);
+}
+EXPORT_SYMBOL_GPL(sdhci_enable_v4_mode);
+
 static inline bool sdhci_data_line_cmd(struct mmc_command *cmd)
 {
 	return cmd->data || cmd->flags & MMC_RSP_BUSY;
@@ -252,6 +275,9 @@ static void sdhci_init(struct sdhci_host *host, int soft)
 	else
 		sdhci_do_reset(host, SDHCI_RESET_ALL);
 
+	if (host->v4_mode)
+		sdhci_do_enable_v4_mode(host);
+
 	sdhci_set_default_irqs(host);
 
 	host->cqe_on = false;
@@ -3394,6 +3420,9 @@ void __sdhci_read_caps(struct sdhci_host *host, u16 *ver, u32 *caps, u32 *caps1)
 
 	sdhci_do_reset(host, SDHCI_RESET_ALL);
 
+	if (host->v4_mode)
+		sdhci_do_enable_v4_mode(host);
+
 	of_property_read_u64(mmc_dev(host->mmc)->of_node,
 			     "sdhci-caps-mask", &dt_caps_mask);
 	of_property_read_u64(mmc_dev(host->mmc)->of_node,

drivers/mmc/host/sdhci.h

@@ -184,6 +184,7 @@
 #define   SDHCI_CTRL_DRV_TYPE_D		0x0030
 #define  SDHCI_CTRL_EXEC_TUNING		0x0040
 #define  SDHCI_CTRL_TUNED_CLK		0x0080
+#define  SDHCI_CTRL_V4_MODE		0x1000
 #define  SDHCI_CTRL_PRESET_VAL_ENABLE	0x8000
 
 #define SDHCI_CAPABILITIES	0x40
@@ -504,6 +505,7 @@ struct sdhci_host {
 	bool preset_enabled;	/* Preset is enabled */
 	bool pending_reset;	/* Cmd/data reset is pending */
 	bool irq_wake_enabled;	/* IRQ wakeup is enabled */
+	bool v4_mode;		/* Host Version 4 Enable */
 
 	struct mmc_request *mrqs_done[SDHCI_MAX_MRQS];	/* Requests done */
 	struct mmc_command *cmd;	/* Current command */
@@ -759,6 +761,7 @@ bool sdhci_cqe_irq(struct sdhci_host *host, u32 intmask, int *cmd_error,
 		   int *data_error);
 
 void sdhci_dumpregs(struct sdhci_host *host);
+void sdhci_enable_v4_mode(struct sdhci_host *host);
 
 void sdhci_start_tuning(struct sdhci_host *host);
 void sdhci_end_tuning(struct sdhci_host *host);