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>

2 files changed, 9 insertions, 3 deletions

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index d5febe584b0..9e15f41f87b 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/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
diff --git a/include/linux/mmc/sdhci.h b/include/linux/mmc/sdhci.h
index 0d953f513d8..83bd9f76709 100644
--- a/include/linux/mmc/sdhci.h
+++ b/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 */