mmc: sdhci: add SDHCI_QUIRK_BROKEN_HISPD_MODE

Some IP-core implementations of the SDHCI have different troubles on the
silicon where they are placed.

On ZYNQ platform for example Xilinx doesn't accept the hold timing of an
eMMC chip which operates in High-Speed mode and must be forced to
operate in non high-speed mode. To get rid of this
"SDHCI_QUIRK_BROKEN_HISPD_MODE" is introduced.

For more details about this refer to the Xilinx answer-recor #59999
https://www.xilinx.com/support/answers/59999.html

This commit:
- doesn't set HISPD bit on the host-conroller
- reflects this fact within the host-controller capabilities

Upon this the layer above (mmc-driver) can setup the card correctly.

Otherwise the MMC card will be switched into high-speed mode and causes
possible timing violation on the host-controller side.

Signed-off-by: Hannes Schmelzer <oe5hpm@oevsv.at>

Signed-off-by: Hannes Schmelzer <hannes.schmelzer@br-automation.com>

drivers/mmc/sdhci.c

@@ -462,7 +462,8 @@ static int sdhci_set_ios(struct mmc *mmc)
 	else
 		ctrl &= ~SDHCI_CTRL_HISPD;
 
-	if (host->quirks & SDHCI_QUIRK_NO_HISPD_BIT)
+	if ((host->quirks & SDHCI_QUIRK_NO_HISPD_BIT) ||
+	    (host->quirks & SDHCI_QUIRK_BROKEN_HISPD_MODE))
 		ctrl &= ~SDHCI_CTRL_HISPD;
 
 	sdhci_writeb(host, ctrl, SDHCI_HOST_CONTROL);
@@ -602,6 +603,11 @@ int sdhci_setup_cfg(struct mmc_config *cfg, struct sdhci_host *host,
 			cfg->host_caps &= ~MMC_MODE_8BIT;
 	}
 
+	if (host->quirks & SDHCI_QUIRK_BROKEN_HISPD_MODE) {
+		cfg->host_caps &= ~MMC_MODE_HS;
+		cfg->host_caps &= ~MMC_MODE_HS_52MHz;
+	}
+
 	if (host->host_caps)
 		cfg->host_caps |= host->host_caps;
 

include/sdhci.h

@@ -213,6 +213,12 @@
 #define SDHCI_QUIRK_BROKEN_R1B		(1 << 2)
 #define SDHCI_QUIRK_NO_HISPD_BIT	(1 << 3)
 #define SDHCI_QUIRK_BROKEN_VOLTAGE	(1 << 4)
+/*
+ * SDHCI_QUIRK_BROKEN_HISPD_MODE
+ * the hardware cannot operate correctly in high-speed mode,
+ * this quirk forces the sdhci host-controller to non high-speed mode
+ */
+#define SDHCI_QUIRK_BROKEN_HISPD_MODE	BIT(5)
 #define SDHCI_QUIRK_WAIT_SEND_CMD	(1 << 6)
 #define SDHCI_QUIRK_USE_WIDE8		(1 << 8)