mmc: sdhci-of-esdhc: add support for signal voltage switch

eSDHC supports signal voltage switch from 3.3v to 1.8v by
eSDHC_PROCTL[VOLT_SEL] bit. This bit changes the value of output
signal SDHC_VS, and there must be a control circuit out of eSDHC
to change the signal voltage according to SDHC_VS output signal.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

2 files changed, 75 insertions, 0 deletions

diff --git a/drivers/mmc/host/sdhci-esdhc.h b/drivers/mmc/host/sdhci-esdhc.h
index 5343fc062e22..68695679fed5 100644
--- a/drivers/mmc/host/sdhci-esdhc.h
+++ b/drivers/mmc/host/sdhci-esdhc.h
@@ -37,6 +37,7 @@
 
 /* Protocol Control Register */
 #define ESDHC_PROCTL                    0x28
+#define ESDHC_VOLT_SEL                  0x00000400
 #define ESDHC_CTRL_4BITBUS              (0x1 << 1)
 #define ESDHC_CTRL_8BITBUS              (0x2 << 1)
 #define ESDHC_CTRL_BUSWIDTH_MASK        (0x3 << 1)
diff --git a/drivers/mmc/host/sdhci-of-esdhc.c b/drivers/mmc/host/sdhci-of-esdhc.c
index 0b3f05ae8328..f2d7002e37c1 100644
--- a/drivers/mmc/host/sdhci-of-esdhc.c
+++ b/drivers/mmc/host/sdhci-of-esdhc.c
@@ -16,6 +16,7 @@
 #include <linux/err.h>
 #include <linux/io.h>
 #include <linux/of.h>
+#include <linux/of_address.h>
 #include <linux/delay.h>
 #include <linux/module.h>
 #include <linux/sys_soc.h>
@@ -560,6 +561,76 @@ static void esdhc_reset(struct sdhci_host *host, u8 mask)
         sdhci_writel(host, host->ier, SDHCI_SIGNAL_ENABLE);
 }
 
+/* The SCFG, Supplemental Configuration Unit, provides SoC specific
+ * configuration and status registers for the device. There is a
+ * SDHC IO VSEL control register on SCFG for some platforms. It's
+ * used to support SDHC IO voltage switching.
+ */
+static const struct of_device_id scfg_device_ids[] = {
+        { .compatible = "fsl,t1040-scfg", },
+        { .compatible = "fsl,ls1012a-scfg", },
+        { .compatible = "fsl,ls1046a-scfg", },
+        {}
+};
+
+/* SDHC IO VSEL control register definition */
+#define SCFG_SDHCIOVSELCR       0x408
+#define SDHCIOVSELCR_TGLEN      0x80000000
+#define SDHCIOVSELCR_VSELVAL    0x60000000
+#define SDHCIOVSELCR_SDHC_VS    0x00000001
+
+static int esdhc_signal_voltage_switch(struct mmc_host *mmc,
+                                       struct mmc_ios *ios)
+{
+        struct sdhci_host *host = mmc_priv(mmc);
+        struct device_node *scfg_node;
+        void __iomem *scfg_base = NULL;
+        u32 sdhciovselcr;
+        u32 val;
+
+        /*
+         * Signal Voltage Switching is only applicable for Host Controllers
+         * v3.00 and above.
+         */
+        if (host->version < SDHCI_SPEC_300)
+                return 0;
+
+        val = sdhci_readl(host, ESDHC_PROCTL);
+
+        switch (ios->signal_voltage) {
+        case MMC_SIGNAL_VOLTAGE_330:
+                val &= ~ESDHC_VOLT_SEL;
+                sdhci_writel(host, val, ESDHC_PROCTL);
+                return 0;
+        case MMC_SIGNAL_VOLTAGE_180:
+                scfg_node = of_find_matching_node(NULL, scfg_device_ids);
+                if (scfg_node)
+                        scfg_base = of_iomap(scfg_node, 0);
+                if (scfg_base) {
+                        sdhciovselcr = SDHCIOVSELCR_TGLEN |
+                                       SDHCIOVSELCR_VSELVAL;
+                        iowrite32be(sdhciovselcr,
+                                scfg_base + SCFG_SDHCIOVSELCR);
+
+                        val |= ESDHC_VOLT_SEL;
+                        sdhci_writel(host, val, ESDHC_PROCTL);
+                        mdelay(5);
+
+                        sdhciovselcr = SDHCIOVSELCR_TGLEN |
+                                       SDHCIOVSELCR_SDHC_VS;
+                        iowrite32be(sdhciovselcr,
+                                scfg_base + SCFG_SDHCIOVSELCR);
+                        iounmap(scfg_base);
+                } else {
+                        val |= ESDHC_VOLT_SEL;
+                        sdhci_writel(host, val, ESDHC_PROCTL);
+                }
+                return 0;
+        default:
+                return 0;
+        }
+}
+
 #ifdef CONFIG_PM_SLEEP
 static u32 esdhc_proctl;
 static int esdhc_of_suspend(struct device *dev)
@@ -717,6 +788,9 @@ static int sdhci_esdhc_probe(struct platform_device *pdev)
         if (IS_ERR(host))
                 return PTR_ERR(host);
 
+        host->mmc_host_ops.start_signal_voltage_switch =
+                esdhc_signal_voltage_switch;
+
         esdhc_init(pdev, host);
 
         sdhci_get_of_property(pdev);