mmc: sdhci-of-esdhc: exit HS400 properly before setting any speed mode

The eSDHC HS400 timing requires many specific registers setting,
unlike other speed modes which need to set only host controller 2
register. When driver needs to downgrade HS400 mode to other speed
mode, the controller have to exit HS400 timing properly first.
This patch is to support the procedure of HS400 exiting at the
beginning of esdhc_set_uhs_signaling.
Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20200522031256.856-1-yangbo.lu@nxp.comSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

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

@@ -1135,6 +1135,40 @@ static int esdhc_execute_tuning(struct mmc_host *mmc, u32 opcode)
 static void esdhc_set_uhs_signaling(struct sdhci_host *host,
 				   unsigned int timing)
 {
+	u32 val;
+
+	/*
+	 * There are specific registers setting for HS400 mode.
+	 * Clean all of them if controller is in HS400 mode to
+	 * exit HS400 mode before re-setting any speed mode.
+	 */
+	val = sdhci_readl(host, ESDHC_TBCTL);
+	if (val & ESDHC_HS400_MODE) {
+		val = sdhci_readl(host, ESDHC_SDTIMNGCTL);
+		val &= ~ESDHC_FLW_CTL_BG;
+		sdhci_writel(host, val, ESDHC_SDTIMNGCTL);
+
+		val = sdhci_readl(host, ESDHC_SDCLKCTL);
+		val &= ~ESDHC_CMD_CLK_CTL;
+		sdhci_writel(host, val, ESDHC_SDCLKCTL);
+
+		esdhc_clock_enable(host, false);
+		val = sdhci_readl(host, ESDHC_TBCTL);
+		val &= ~ESDHC_HS400_MODE;
+		sdhci_writel(host, val, ESDHC_TBCTL);
+		esdhc_clock_enable(host, true);
+
+		val = sdhci_readl(host, ESDHC_DLLCFG0);
+		val &= ~(ESDHC_DLL_ENABLE | ESDHC_DLL_FREQ_SEL);
+		sdhci_writel(host, val, ESDHC_DLLCFG0);
+
+		val = sdhci_readl(host, ESDHC_TBCTL);
+		val &= ~ESDHC_HS400_WNDW_ADJUST;
+		sdhci_writel(host, val, ESDHC_TBCTL);
+
+		esdhc_tuning_block_enable(host, false);
+	}
+
 	if (timing == MMC_TIMING_MMC_HS400)
 		esdhc_tuning_block_enable(host, true);
 	else