mmc: sdhci-esdhc-imx: support setting tuning start point

The delay cells of some SoCs may have less delay per one cell,
for such SoCs, user could set the start delay cell point to bypass
the first a few meaningless tuning commands.
Acked-by: NAdrian Hunter <adrian.hunter@intel.com>
Signed-off-by: NDong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>

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

@@ -76,7 +76,8 @@
 #define ESDHC_TUNING_CTRL		0xcc
 #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_START_TAP_DEFAULT	0x1
+#define ESDHC_TUNING_START_TAP_MASK	0xff
 #define ESDHC_TUNING_STEP_MASK		0x00070000
 #define ESDHC_TUNING_STEP_SHIFT		16
 
@@ -490,7 +491,12 @@ static void esdhc_writew_le(struct sdhci_host *host, u16 val, int reg)
 				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;
+				tuning_ctrl |= ESDHC_STD_TUNING_EN | ESDHC_TUNING_START_TAP_DEFAULT;
+				if (imx_data->boarddata.tuning_start_tap) {
+					tuning_ctrl &= ~ESDHC_TUNING_START_TAP_MASK;
+					tuning_ctrl |= imx_data->boarddata.tuning_start_tap;
+				}
+
 				if (imx_data->boarddata.tuning_step) {
 					tuning_ctrl &= ~ESDHC_TUNING_STEP_MASK;
 					tuning_ctrl |= imx_data->boarddata.tuning_step << ESDHC_TUNING_STEP_SHIFT;
@@ -976,6 +982,8 @@ sdhci_esdhc_imx_probe_dt(struct platform_device *pdev,
 		boarddata->wp_type = ESDHC_WP_GPIO;
 
 	of_property_read_u32(np, "fsl,tuning-step", &boarddata->tuning_step);
+	of_property_read_u32(np, "fsl,tuning-start-tap",
+			     &boarddata->tuning_start_tap);
 
 	if (of_find_property(np, "no-1-8-v", NULL))
 		boarddata->support_vsel = false;
@@ -1198,7 +1206,7 @@ static int sdhci_esdhc_imx_probe(struct platform_device *pdev)
 
 	if (imx_data->socdata->flags & ESDHC_FLAG_STD_TUNING)
 		writel(readl(host->ioaddr + ESDHC_TUNING_CTRL) |
-			ESDHC_STD_TUNING_EN | ESDHC_TUNING_START_TAP,
+			ESDHC_STD_TUNING_EN | ESDHC_TUNING_START_TAP_DEFAULT,
 			host->ioaddr + ESDHC_TUNING_CTRL);
 
 	if (imx_data->socdata->flags & ESDHC_FLAG_ERR004536)

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

@@ -46,5 +46,6 @@ struct esdhc_platform_data {
 	bool support_vsel;
 	unsigned int delay_line;
 	unsigned int tuning_step;       /* The delay cell steps in tuning procedure */
+	unsigned int tuning_start_tap;	/* The start delay cell point in tuning procedure */
 };
 #endif /* __ASM_ARCH_IMX_ESDHC_H */