mmc: sdhci-of-arasan: implement enhanced strobe callback

Currently sdhci-arasan 5.1 can support enhanced strobe function,
and we now limit it just for "arasan,sdhci-5.1". Add
mmc-hs400-enhanced-strobe in DT to enable the function if we're
sure our controller can support it.
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Tested-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci-of-arasan.c

@@ -25,7 +25,9 @@
 #include "sdhci-pltfm.h"
 
 #define SDHCI_ARASAN_CLK_CTRL_OFFSET	0x2c
+#define SDHCI_ARASAN_VENDOR_REGISTER	0x78
 
+#define VENDOR_ENHANCED_STROBE		BIT(0)
 #define CLK_CTRL_TIMEOUT_SHIFT		16
 #define CLK_CTRL_TIMEOUT_MASK		(0xf << CLK_CTRL_TIMEOUT_SHIFT)
 #define CLK_CTRL_TIMEOUT_MIN_EXP	13
@@ -79,6 +81,21 @@ static void sdhci_arasan_set_clock(struct sdhci_host *host, unsigned int clock)
 	}
 }
 
+static void sdhci_arasan_hs400_enhanced_strobe(struct mmc_host *mmc,
+					struct mmc_ios *ios)
+{
+	u32 vendor;
+	struct sdhci_host *host = mmc_priv(mmc);
+
+	vendor = readl(host->ioaddr + SDHCI_ARASAN_VENDOR_REGISTER);
+	if (ios->enhanced_strobe)
+		vendor |= VENDOR_ENHANCED_STROBE;
+	else
+		vendor &= ~VENDOR_ENHANCED_STROBE;
+
+	writel(vendor, host->ioaddr + SDHCI_ARASAN_VENDOR_REGISTER);
+}
+
 static struct sdhci_ops sdhci_arasan_ops = {
 	.set_clock = sdhci_arasan_set_clock,
 	.get_max_clock = sdhci_pltfm_clk_get_max_clock,
@@ -245,6 +262,9 @@ static int sdhci_arasan_probe(struct platform_device *pdev)
 			dev_err(&pdev->dev, "phy_power_on err.\n");
 			goto err_phy_power;
 		}
+
+		host->mmc_host_ops.hs400_enhanced_strobe =
+					sdhci_arasan_hs400_enhanced_strobe;
 	}
 
 	ret = sdhci_add_host(host);