sdhci: Add support for hosts that are only capable of 1-bit transfers

Some hosts (hardware configurations, or particular SD/MMC slots) may
not support 4-bit bus. For example, on MPC8569E-MDS boards we can
switch between serial (1-bit only) and nibble (4-bit) modes, thought
we have to disable more peripherals to work in 4-bit mode.

Along with some small core changes, this patch modifies sdhci-of
driver, so that now it looks for "sdhci,1-bit-only" property in the
device-tree, and if specified we enable a proper quirk.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Pierre Ossman <pierre@ossman.eu>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index 84d149096f0..5d37dd94b53 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -228,6 +228,8 @@ struct sdhci_host {
 #define SDHCI_QUIRK_FORCE_BLK_SZ_2048                   (1<<20)
 /* Controller cannot do multi-block transfers */
 #define SDHCI_QUIRK_NO_MULTIBLOCK                       (1<<21)
+/* Controller can only handle 1-bit data transfers */
+#define SDHCI_QUIRK_FORCE_1_BIT_DATA                    (1<<22)
 
         int                     irq;            /* Device IRQ */
         void __iomem *          ioaddr;         /* Mapped address */