mmc: sdhci: add quirk for max len ADMA descriptors

Some controllers misparse segment length 0 as being 0, not 65536. Add
a quirk to deal with it.
Signed-off-by: Olof Johansson <olof@lixom.net>
Reviewed-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/host/sdhci.c

@@ -1949,10 +1949,14 @@ int sdhci_add_host(struct sdhci_host *host)
 	 * of bytes. When doing hardware scatter/gather, each entry cannot
 	 * be larger than 64 KiB though.
 	 */
-	if (host->flags & SDHCI_USE_ADMA)
-		mmc->max_seg_size = 65536;
-	else
+	if (host->flags & SDHCI_USE_ADMA) {
+		if (host->quirks & SDHCI_QUIRK_BROKEN_ADMA_ZEROLEN_DESC)
+			mmc->max_seg_size = 65535;
+		else
+			mmc->max_seg_size = 65536;
+	} else {
 		mmc->max_seg_size = mmc->max_req_size;
+	}
 
 	/*
 	 * Maximum block size. This varies from controller to controller and

include/linux/mmc/sdhci.h

@@ -83,6 +83,8 @@ struct sdhci_host {
 #define SDHCI_QUIRK_MULTIBLOCK_READ_ACMD12		(1<<28)
 /* Controller doesn't have HISPD bit field in HI-SPEED SD card */
 #define SDHCI_QUIRK_NO_HISPD_BIT			(1<<29)
+/* Controller treats ADMA descriptors with length 0000h incorrectly */
+#define SDHCI_QUIRK_BROKEN_ADMA_ZEROLEN_DESC		(1<<30)
 
 	int irq;		/* Device IRQ */
 	void __iomem *ioaddr;	/* Mapped address */