mmc: sdhci-sprd: Add HS400 enhanced strobe mode

Add HS400 enhanced strobe mode support for Spreadtrum SD host controller.
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci-sprd.c

@@ -41,6 +41,7 @@
 /* SDHCI_HOST_CONTROL2 */
 #define  SDHCI_SPRD_CTRL_HS200		0x0005
 #define  SDHCI_SPRD_CTRL_HS400		0x0006
+#define  SDHCI_SPRD_CTRL_HS400ES	0x0007
 
 /*
  * According to the standard specification, BIT(3) of SDHCI_SOFTWARE_RESET is
@@ -132,6 +133,15 @@ static inline void sdhci_sprd_sd_clk_off(struct sdhci_host *host)
 	sdhci_writew(host, ctrl, SDHCI_CLOCK_CONTROL);
 }
 
+static inline void sdhci_sprd_sd_clk_on(struct sdhci_host *host)
+{
+	u16 ctrl;
+
+	ctrl = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
+	ctrl |= SDHCI_CLOCK_CARD_EN;
+	sdhci_writew(host, ctrl, SDHCI_CLOCK_CONTROL);
+}
+
 static inline void
 sdhci_sprd_set_dll_invert(struct sdhci_host *host, u32 mask, bool en)
 {
@@ -325,6 +335,26 @@ static void sdhci_sprd_request(struct mmc_host *mmc, struct mmc_request *mrq)
 	sdhci_request(mmc, mrq);
 }
 
+static void sdhci_sprd_hs400_enhanced_strobe(struct mmc_host *mmc,
+					     struct mmc_ios *ios)
+{
+	struct sdhci_host *host = mmc_priv(mmc);
+	u16 ctrl_2;
+
+	if (!ios->enhanced_strobe)
+		return;
+
+	sdhci_sprd_sd_clk_off(host);
+
+	/* Set HS400 enhanced strobe mode */
+	ctrl_2 = sdhci_readw(host, SDHCI_HOST_CONTROL2);
+	ctrl_2 &= ~SDHCI_CTRL_UHS_MASK;
+	ctrl_2 |= SDHCI_SPRD_CTRL_HS400ES;
+	sdhci_writew(host, ctrl_2, SDHCI_HOST_CONTROL2);
+
+	sdhci_sprd_sd_clk_on(host);
+}
+
 static const struct sdhci_pltfm_data sdhci_sprd_pdata = {
 	.quirks = SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK,
 	.quirks2 = SDHCI_QUIRK2_BROKEN_HS200 |
@@ -346,6 +376,8 @@ static int sdhci_sprd_probe(struct platform_device *pdev)
 	host->dma_mask = DMA_BIT_MASK(64);
 	pdev->dev.dma_mask = &host->dma_mask;
 	host->mmc_host_ops.request = sdhci_sprd_request;
+	host->mmc_host_ops.hs400_enhanced_strobe =
+		sdhci_sprd_hs400_enhanced_strobe;
 
 	host->mmc->caps = MMC_CAP_SD_HIGHSPEED | MMC_CAP_MMC_HIGHSPEED |
 		MMC_CAP_ERASE | MMC_CAP_CMD23;