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, 4 insertions, 1 deletions

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;