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>

4 files changed, 11 insertions, 1 deletions

diff --git a/Documentation/powerpc/dts-bindings/fsl/esdhc.txt b/Documentation/powerpc/dts-bindings/fsl/esdhc.txt
index 5093ddf900da..3ed3797b5086 100644
--- a/Documentation/powerpc/dts-bindings/fsl/esdhc.txt
+++ b/Documentation/powerpc/dts-bindings/fsl/esdhc.txt
@@ -10,6 +10,8 @@ Required properties:
   - interrupts : should contain eSDHC interrupt.
   - interrupt-parent : interrupt source phandle.
   - clock-frequency : specifies eSDHC base clock frequency.
+  - sdhci,1-bit-only : (optional) specifies that a controller can
+    only handle 1-bit data transfers.
 
 Example:
 
diff --git a/drivers/mmc/host/sdhci-of.c b/drivers/mmc/host/sdhci-of.c
index 128c614d11aa..d79fa55c3b89 100644
--- a/drivers/mmc/host/sdhci-of.c
+++ b/drivers/mmc/host/sdhci-of.c
@@ -250,6 +250,9 @@ static int __devinit sdhci_of_probe(struct of_device *ofdev,
                 host->ops = &sdhci_of_data->ops;
         }
 
+        if (of_get_property(np, "sdhci,1-bit-only", NULL))
+                host->quirks |= SDHCI_QUIRK_FORCE_1_BIT_DATA;
+
         clk = of_get_property(np, "clock-frequency", &size);
         if (clk && size == sizeof(*clk) && *clk)
                 of_host->clock = *clk;
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 3856669aa7e8..c7586739be1e 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1761,7 +1761,10 @@ int sdhci_add_host(struct sdhci_host *host)
         mmc->ops = &sdhci_ops;
         mmc->f_min = host->max_clk / 256;
         mmc->f_max = host->max_clk;
-        mmc->caps = MMC_CAP_4_BIT_DATA | MMC_CAP_SDIO_IRQ;
+        mmc->caps = MMC_CAP_SDIO_IRQ;
+
+        if (!(host->quirks & SDHCI_QUIRK_FORCE_1_BIT_DATA))
+                mmc->caps |= MMC_CAP_4_BIT_DATA;
 
         if (caps & SDHCI_CAN_DO_HISPD)
                 mmc->caps |= MMC_CAP_SD_HIGHSPEED;
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index 84d149096f0e..5d37dd94b53f 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 */