mmc: sdhci-esdhc-imx: add tuning-step setting support

tuning-step is the delay cell steps in tuning procedure. The default value
of tuning-step is 1. Some boards or cards need another value to pass the
tuning procedure. For example, imx7d-sdb board need the tuning-step value
as 2, otherwise it can't pass the tuning procedure.

So this patch add the tuning-step setting in driver, so that user can set
the tuning-step value in dts.

Signed-off-by: Haibo Chen <[e-mail]>
Acked-by: Dong Aisheng <[e-mail]>
Signed-off-by: Ulf Hansson <[e-mail]>

drivers/mmc/host/sdhci-esdhc-imx.c

···
 #define ESDHC_STD_TUNING_EN		(1 << 24)
 /* NOTE: the minimum valid tuning start tap for mx6sl is 1 */
 #define ESDHC_TUNING_START_TAP		0x1
+#define ESDHC_TUNING_STEP_SHIFT		16
 
 /* pinctrl state */
 #define ESDHC_PINCTRL_STATE_100MHZ	"state_100mhz"
···
 		} else if (imx_data->socdata->flags & ESDHC_FLAG_STD_TUNING) {
 			u32 v = readl(host->ioaddr + SDHCI_ACMD12_ERR);
 			u32 m = readl(host->ioaddr + ESDHC_MIX_CTRL);
+			u32 tuning_ctrl;
 			if (val & SDHCI_CTRL_TUNED_CLK) {
 				v |= ESDHC_MIX_CTRL_SMPCLK_SEL;
 			} else {
···
 			if (val & SDHCI_CTRL_EXEC_TUNING) {
 				v |= ESDHC_MIX_CTRL_EXE_TUNE;
 				m |= ESDHC_MIX_CTRL_FBCLK_SEL;
+				tuning_ctrl = readl(host->ioaddr + ESDHC_TUNING_CTRL);
+				tuning_ctrl |= ESDHC_STD_TUNING_EN | ESDHC_TUNING_START_TAP;
+				if (imx_data->boarddata.tuning_step)
+					tuning_ctrl |= imx_data->boarddata.tuning_step << ESDHC_TUNING_STEP_SHIFT;
+					writel(tuning_ctrl, host->ioaddr + ESDHC_TUNING_CTRL);
 			} else {
 				v &= ~ESDHC_MIX_CTRL_EXE_TUNE;
 			}
···
 	boarddata->wp_gpio = of_get_named_gpio(np, "wp-gpios", 0);
 	if (gpio_is_valid(boarddata->wp_gpio))
 		boarddata->wp_type = ESDHC_WP_GPIO;
+
+	of_property_read_u32(np, "fsl,tuning-step", &boarddata->tuning_step);
 
 	if (of_find_property(np, "no-1-8-v", NULL))
 		boarddata->support_vsel = false;

include/linux/platform_data/mmc-esdhc-imx.h

···
 	int max_bus_width;
 	bool support_vsel;
 	unsigned int delay_line;
+	unsigned int tuning_step;       /* The delay cell steps in tuning procedure */
 };
 #endif /* __ASM_ARCH_IMX_ESDHC_H */