mmc: sunxi: add support for automatic delay calibration

A64 and H6 support automatic delay calibration and Linux driver uses it
instead of hardcoded delays. Add support for it to u-boot driver.

Fixes eMMC instability on Pinebook

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Tested-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Cc: Vagrant Cascadian <vagrant@debian.org>
Reviewed-by: Jagan Teki <jagan@openedev.com>

arch/arm/include/asm/arch-sunxi/mmc.h

@@ -46,7 +46,9 @@ struct sunxi_mmc {
 	u32 cbda;		/* 0x94 */
 	u32 res2[26];
 #if defined(CONFIG_SUNXI_GEN_SUN6I) || defined(CONFIG_MACH_SUN50I_H6)
-	u32 res3[64];
+	u32 res3[17];
+	u32 samp_dl;
+	u32 res4[46];
 #endif
 	u32 fifo;		/* 0x100 / 0x200 FIFO access address */
 };
@@ -130,5 +132,7 @@ struct sunxi_mmc {
 #define SUNXI_MMC_COMMON_CLK_GATE		(1 << 16)
 #define SUNXI_MMC_COMMON_RESET			(1 << 18)
 
+#define SUNXI_MMC_CAL_DL_SW_EN		(0x1 << 7)
+
 struct mmc *sunxi_mmc_init(int sdc_no);
 #endif /* _SUNXI_MMC_H */

drivers/mmc/sunxi_mmc.c

@@ -99,11 +99,16 @@ static int mmc_set_mod_clk(struct sunxi_mmc_priv *priv, unsigned int hz)
 {
 	unsigned int pll, pll_hz, div, n, oclk_dly, sclk_dly;
 	bool new_mode = false;
+	bool calibrate = false;
 	u32 val = 0;
 
 	if (IS_ENABLED(CONFIG_MMC_SUNXI_HAS_NEW_MODE) && (priv->mmc_no == 2))
 		new_mode = true;
 
+#if defined(CONFIG_MACH_SUN50I) || defined(CONFIG_MACH_SUN50I_H6)
+	calibrate = true;
+#endif
+
 	/*
 	 * The MMC clock has an extra /2 post-divider when operating in the new
 	 * mode.
@@ -174,7 +179,11 @@ static int mmc_set_mod_clk(struct sunxi_mmc_priv *priv, unsigned int hz)
 		val = CCM_MMC_CTRL_MODE_SEL_NEW;
 		setbits_le32(&priv->reg->ntsr, SUNXI_MMC_NTSR_MODE_SEL_NEW);
 #endif
-	} else {
+	} else if (!calibrate) {
+		/*
+		 * Use hardcoded delay values if controller doesn't support
+		 * calibration
+		 */
 		val = CCM_MMC_CTRL_OCLK_DLY(oclk_dly) |
 			CCM_MMC_CTRL_SCLK_DLY(sclk_dly);
 	}
@@ -228,6 +237,16 @@ static int mmc_config_clock(struct sunxi_mmc_priv *priv, struct mmc *mmc)
 	rval &= ~SUNXI_MMC_CLK_DIVIDER_MASK;
 	writel(rval, &priv->reg->clkcr);
 
+#if defined(CONFIG_MACH_SUN50I) || defined(CONFIG_MACH_SUN50I_H6)
+	/* A64 supports calibration of delays on MMC controller and we
+	 * have to set delay of zero before starting calibration.
+	 * Allwinner BSP driver sets a delay only in the case of
+	 * using HS400 which is not supported by mainline U-Boot or
+	 * Linux at the moment
+	 */
+	writel(SUNXI_MMC_CAL_DL_SW_EN, &priv->reg->samp_dl);
+#endif
+
 	/* Re-enable Clock */
 	rval |= SUNXI_MMC_CLK_ENABLE;
 	writel(rval, &priv->reg->clkcr);