mmc: esdhc: Fix bug when writing to SDHCI_HOST_CONTROL register

The P2020 has a non-standard implementation of the SDHCI_HOST_CONTROL
register. This patch adds a QUIRK in the SDHCI header to signal that
a host controller has a non-standard SDHCI_HOST_CONTROL register. The
patch adds a check to the function esdhc_writeb in file
sdhci-of-esdhc.c, where it checks if the write is done to the
SDHCI_HOST_CONTROL register and th host has the above mentioned QUIRK,
then the function simply returns instead of writing to the register.
The patch also detects if the processor is P2020 (by looking in dev
tree) and if so, adds the QUIRK to the host->quirk2

Signed-off-by: Oded Gabbay <[e-mail]>
Reviewed-by: Anton Vorontsov <[e-mail]>
Signed-off-by: Chris Ball <[e-mail]>

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

···
 	if (reg == SDHCI_HOST_CONTROL) {
 		u32 dma_bits;
 
+		/*
+		 * If host control register is not standard, exit
+		 * this function
+		 */
+		if (host->quirks2 & SDHCI_QUIRK2_BROKEN_HOST_CONTROL)
+			return;
+
 		/* DMA select is 22,23 bits in Protocol Control Register */
 		dma_bits = (val & SDHCI_CTRL_DMA_MASK) << 5;
 		clrsetbits_be32(host->ioaddr + reg , SDHCI_CTRL_DMA_MASK << 5,
···
 static int sdhci_esdhc_probe(struct platform_device *pdev)
 {
 	struct sdhci_host *host;
+	struct device_node *np;
 	int ret;
 
 	host = sdhci_pltfm_init(pdev, &sdhci_esdhc_pdata, 0);
···
 		return PTR_ERR(host);
 
 	sdhci_get_of_property(pdev);
+
+	np = pdev->dev.of_node;
+	if (of_device_is_compatible(np, "fsl,p2020-esdhc")) {
+		/*
+		 * Freescale messed up with P2020 as it has a non-standard
+		 * host control register
+		 */
+		host->quirks2 |= SDHCI_QUIRK2_BROKEN_HOST_CONTROL;
+	}
 
 	/* call to generic mmc_of_parse to support additional capabilities */
 	mmc_of_parse(host->mmc);

include/linux/mmc/sdhci.h

···
 #define SDHCI_QUIRK2_NO_1_8_V				(1<<2)
 #define SDHCI_QUIRK2_PRESET_VALUE_BROKEN		(1<<3)
 #define SDHCI_QUIRK2_CARD_ON_NEEDS_BUS_ON		(1<<4)
+/* Controller has a non-standard host control register */
+#define SDHCI_QUIRK2_BROKEN_HOST_CONTROL		(1<<5)
 
 	int irq;		/* Device IRQ */
 	void __iomem *ioaddr;	/* Mapped address */