mmc: jz4740: Add support for vqmmc power supply

Support enabling / disabling the vqmmc power supply if it was provided
by the firmware.

Provide the .start_signal_voltage_switch callback to change the voltage
of the external vqmmc power supply.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20230131210229.68129-2-paul@crapouillou.netSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/jz4740_mmc.c

@@ -21,6 +21,7 @@
 #include <linux/of_device.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
 #include <linux/scatterlist.h>
 
 #include <asm/cacheflush.h>
@@ -158,6 +159,8 @@ struct jz4740_mmc_host {
 	struct mmc_request *req;
 	struct mmc_command *cmd;
 
+	bool vqmmc_enabled;
+
 	unsigned long waiting;
 
 	uint32_t cmdat;
@@ -935,6 +938,8 @@ static void jz4740_mmc_request(struct mmc_host *mmc, struct mmc_request *req)
 static void jz4740_mmc_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 {
 	struct jz4740_mmc_host *host = mmc_priv(mmc);
+	int ret;
+
 	if (ios->clock)
 		jz4740_mmc_set_clock_rate(host, ios->clock);
 
@@ -947,12 +952,25 @@ static void jz4740_mmc_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 		clk_prepare_enable(host->clk);
 		break;
 	case MMC_POWER_ON:
+		if (!IS_ERR(mmc->supply.vqmmc) && !host->vqmmc_enabled) {
+			ret = regulator_enable(mmc->supply.vqmmc);
+			if (ret)
+				dev_err(&host->pdev->dev, "Failed to set vqmmc power!\n");
+			else
+				host->vqmmc_enabled = true;
+		}
 		break;
-	default:
+	case MMC_POWER_OFF:
 		if (!IS_ERR(mmc->supply.vmmc))
 			mmc_regulator_set_ocr(mmc, mmc->supply.vmmc, 0);
+		if (!IS_ERR(mmc->supply.vqmmc) && host->vqmmc_enabled) {
+			regulator_disable(mmc->supply.vqmmc);
+			host->vqmmc_enabled = false;
+		}
 		clk_disable_unprepare(host->clk);
 		break;
+	default:
+		break;
 	}
 
 	switch (ios->bus_width) {
@@ -978,6 +996,23 @@ static void jz4740_mmc_enable_sdio_irq(struct mmc_host *mmc, int enable)
 	jz4740_mmc_set_irq_enabled(host, JZ_MMC_IRQ_SDIO, enable);
 }
 
+static int jz4740_voltage_switch(struct mmc_host *mmc, struct mmc_ios *ios)
+{
+	int ret;
+
+	/* vqmmc regulator is available */
+	if (!IS_ERR(mmc->supply.vqmmc)) {
+		ret = mmc_regulator_set_vqmmc(mmc, ios);
+		return ret < 0 ? ret : 0;
+	}
+
+	/* no vqmmc regulator, assume fixed regulator at 3/3.3V */
+	if (ios->signal_voltage == MMC_SIGNAL_VOLTAGE_330)
+		return 0;
+
+	return -EINVAL;
+}
+
 static const struct mmc_host_ops jz4740_mmc_ops = {
 	.request	= jz4740_mmc_request,
 	.pre_req	= jz4740_mmc_pre_request,
@@ -986,6 +1021,7 @@ static const struct mmc_host_ops jz4740_mmc_ops = {
 	.get_ro		= mmc_gpio_get_ro,
 	.get_cd		= mmc_gpio_get_cd,
 	.enable_sdio_irq = jz4740_mmc_enable_sdio_irq,
+	.start_signal_voltage_switch = jz4740_voltage_switch,
 };
 
 static const struct of_device_id jz4740_mmc_of_match[] = {