[PATCH 20/30] mci: imx-esdhc: add support for setting drive strength

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

With increasing clock rates, drive strength may need to be reduced. Add
support for that to the i.MX eSDHC driver and to the core.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 drivers/mci/imx-esdhc.c |  2 ++
 drivers/mci/mci-core.c  | 40 ++++++++++++++++++++++++++++++++++++++--
 drivers/mci/sdhci.c     | 29 +++++++++++++++++++++++++++++
 drivers/mci/sdhci.h     |  6 ++++++
 include/mci.h           | 10 ++++++++++
 5 files changed, 85 insertions(+), 2 deletions(-)

diff --git a/drivers/mci/imx-esdhc.c b/drivers/mci/imx-esdhc.c
index 9d82c886cdcf..5f427a1898b7 100644
--- a/drivers/mci/imx-esdhc.c
+++ b/drivers/mci/imx-esdhc.c
@@ -207,6 +207,8 @@ static void esdhc_set_ios(struct mci_host *mci, struct mci_ios *ios)
 	/* Set the clock speed */
 	set_sysctl(mci, ios->clock, mci_timing_is_ddr(ios->timing));
 
+	sdhci_set_drv_type(&host->sdhci, ios->drv_type);
+
 	/* Set the bus width */
 	esdhc_clrbits32(host, SDHCI_HOST_CONTROL__POWER_CONTROL__BLOCK_GAP_CONTROL,
 			PROCTL_DTW_4 | PROCTL_DTW_8);
diff --git a/drivers/mci/mci-core.c b/drivers/mci/mci-core.c
index 14d99d01b441..e5242a9f5add 100644
--- a/drivers/mci/mci-core.c
+++ b/drivers/mci/mci-core.c
@@ -1626,6 +1626,28 @@ int mci_send_abort_tuning(struct mci *mci, u32 opcode)
 }
 EXPORT_SYMBOL_GPL(mci_send_abort_tuning);
 
+static void mmc_select_driver_type(struct mci *mci)
+{
+	int card_drv_type, drive_strength;
+	int fixed_drv_type = mci->host->fixed_drv_type;
+
+	card_drv_type = mci->ext_csd[EXT_CSD_DRIVER_STRENGTH] |
+			mmc_driver_type_mask(0);
+
+	if (mci->host->fixed_drv_type_valid)
+		drive_strength = card_drv_type & mmc_driver_type_mask(fixed_drv_type)
+				 ? fixed_drv_type : 0;
+	else
+		drive_strength = 0;
+
+	mci->host->drive_strength = drive_strength;
+
+	/* Linux only sets the drive strength immediately if the driver
+	 * implements select_drive_strength, which none of our drivers
+	 * do yet
+	 */
+}
+
 static void mmc_select_max_dtr(struct mci *mci)
 {
 	u8 card_type = mci->ext_csd[EXT_CSD_DEVICE_TYPE];
@@ -1698,6 +1720,8 @@ static int mmc_select_hs200(struct mci *mci)
 	int err = -EINVAL;
 	u8 val;
 
+	mmc_select_driver_type(mci);
+
 	/*
 	 * Set the bus width(4 or 8) with host's support and
 	 * switch to HS200 mode if bus width is set successfully.
@@ -1705,8 +1729,7 @@ static int mmc_select_hs200(struct mci *mci)
 	/* find out maximum bus width and then try DDR if supported */
 	err = mci_mmc_select_bus_width(mci);
 	if (err > 0) {
-		/* TODO  actually set drive strength instead of 0. Currently unsupported. */
-		val = EXT_CSD_TIMING_HS200 | 0 << EXT_CSD_DRV_STR_SHIFT;
+		val = EXT_CSD_TIMING_HS200 | (mci->host->drive_strength << EXT_CSD_DRV_STR_SHIFT);
 		err = mci_switch(mci, EXT_CSD_HS_TIMING, val);
 		if (err == -EIO)
 			return -EBADMSG;
@@ -3091,6 +3114,8 @@ void mci_of_parse_node(struct mci_host *host,
 	if (of_property_read_bool(np, "no-mmc"))
 		host->caps2 |= MMC_CAP2_NO_MMC;
 	if (IS_ENABLED(CONFIG_MCI_TUNING)) {
+		u32 drv_type;
+
 		if (of_property_read_bool(np, "mmc-hs200-1_8v"))
 			host->caps2 |= MMC_CAP2_HS200_1_8V_SDR;
 		if (of_property_read_bool(np, "mmc-hs200-1_2v"))
@@ -3115,6 +3140,17 @@ void mci_of_parse_node(struct mci_host *host,
 			 */
 			host->caps2 &= ~(MMC_CAP2_HSX00_1_8V | MMC_CAP2_HS400_ES);
 		}
+
+		/* Must be after "non-removable" check */
+		if (of_property_read_u32(np, "fixed-emmc-driver-type", &drv_type) == 0) {
+			if (host->non_removable) {
+				host->fixed_drv_type = drv_type;
+				host->fixed_drv_type_valid = true;
+			 } else {
+				dev_err(host->hw_dev,
+					"can't use fixed driver type, media is removable\n");
+			 }
+		}
 	}
 }
 
diff --git a/drivers/mci/sdhci.c b/drivers/mci/sdhci.c
index fe0c0001f9de..4af49d6cb5db 100644
--- a/drivers/mci/sdhci.c
+++ b/drivers/mci/sdhci.c
@@ -893,6 +893,35 @@ void sdhci_set_clock(struct sdhci *host, unsigned int clock, unsigned int input_
 	sdhci_enable_clk(host, clk);
 }
 
+void sdhci_set_drv_type(struct sdhci *host, unsigned drv_type)
+{
+	u16 ctrl_2;
+
+	if (host->preset_enabled)
+		return;
+
+	/*
+	 * We only need to set Driver Strength if the
+	 * preset value enable is not set.
+	 */
+	ctrl_2 = sdhci_read16(host, SDHCI_HOST_CONTROL2);
+	ctrl_2 &= ~SDHCI_CTRL_DRV_TYPE_MASK;
+	if (drv_type == MMC_SET_DRIVER_TYPE_A)
+		ctrl_2 |= SDHCI_CTRL_DRV_TYPE_A;
+	else if (drv_type == MMC_SET_DRIVER_TYPE_B)
+		ctrl_2 |= SDHCI_CTRL_DRV_TYPE_B;
+	else if (drv_type == MMC_SET_DRIVER_TYPE_C)
+		ctrl_2 |= SDHCI_CTRL_DRV_TYPE_C;
+	else if (drv_type == MMC_SET_DRIVER_TYPE_D)
+		ctrl_2 |= SDHCI_CTRL_DRV_TYPE_D;
+	else {
+		dev_warn(sdhci_dev(host), "invalid driver type, default to driver type B\n");
+		ctrl_2 |= SDHCI_CTRL_DRV_TYPE_B;
+	}
+
+	sdhci_write16(host, ctrl_2, SDHCI_HOST_CONTROL2);
+}
+
 static void sdhci_do_enable_v4_mode(struct sdhci *host)
 {
 	u16 ctrl2;
diff --git a/drivers/mci/sdhci.h b/drivers/mci/sdhci.h
index 93303016a584..9c5d192533b0 100644
--- a/drivers/mci/sdhci.h
+++ b/drivers/mci/sdhci.h
@@ -131,6 +131,11 @@
 #define   SDHCI_CTRL_UHS_SDR104			0x3
 #define   SDHCI_CTRL_UHS_DDR50			0x4
 #define   SDHCI_CTRL_HS400			0x5 /* Non-standard */
+#define  SDHCI_CTRL_DRV_TYPE_MASK		GENMASK(5, 4)
+#define   SDHCI_CTRL_DRV_TYPE_B			0x0000
+#define   SDHCI_CTRL_DRV_TYPE_A			0x0010
+#define   SDHCI_CTRL_DRV_TYPE_C			0x0020
+#define   SDHCI_CTRL_DRV_TYPE_D			0x0030
 #define  SDHCI_CTRL_EXEC_TUNING			BIT(6)
 #define  SDHCI_CTRL_TUNED_CLK			BIT(7)
 #define  SDHCI_CTRL_64BIT_ADDR			BIT(13)
@@ -335,6 +340,7 @@ u16 sdhci_calc_clk(struct sdhci *host, unsigned int clock,
 		   unsigned int *actual_clock, unsigned int input_clock);
 void sdhci_set_clock(struct sdhci *host, unsigned int clock, unsigned int input_clock);
 void sdhci_enable_clk(struct sdhci *host, u16 clk);
+void sdhci_set_drv_type(struct sdhci *host, unsigned drv_type);
 void sdhci_enable_v4_mode(struct sdhci *host);
 int sdhci_setup_host(struct sdhci *host);
 void __sdhci_read_caps(struct sdhci *host, const u16 *ver,
diff --git a/include/mci.h b/include/mci.h
index af56f453704e..29aaecb46305 100644
--- a/include/mci.h
+++ b/include/mci.h
@@ -208,6 +208,8 @@
 #define SD_ERASE_ARG			0x00000000
 #define SD_DISCARD_ARG			0x00000001
 
+#define mmc_driver_type_mask(n)		(1 << (n))
+
 /*
  * EXT_CSD fields
  */
@@ -560,6 +562,7 @@ struct mci_ios {
 	unsigned int		clock;			/* clock rate */
 	enum mci_bus_width	bus_width;		/* data bus width */
 	enum mci_timing		timing;			/* timing specification used */
+	unsigned char		drv_type;		/* driver type (A, B, C, D) */
 };
 
 struct mci;
@@ -632,6 +635,13 @@ struct mci_host {
 	int broken_cd;		/**< card detect is broken */
 	bool non_removable;	/**< device is non removable */
 	bool disable_wp;	/**< ignore write-protect detection logic */
+	bool fixed_drv_type_valid;
+	unsigned char fixed_drv_type;	/**< fixed driver type for non-removable media */
+	unsigned char	drive_strength;	/**< driver type (A, B, C, D) */
+#define MMC_SET_DRIVER_TYPE_B	0
+#define MMC_SET_DRIVER_TYPE_A	1
+#define MMC_SET_DRIVER_TYPE_C	2
+#define MMC_SET_DRIVER_TYPE_D	3
 	struct regulator *supply;
 	struct mci_ops ops;
 };
-- 
2.39.5