[PATCH 2/2] MMC: omap_hsmmc: disable multiblock reads when platform_data indicates that they are broken

[Paul Walmsley <paul@pwsan.com>]

When device data indicates that multiple block reads are not supported on
a given HSMMC controller instance, log a message to the console, and
pass the appropriate MMC capability flag to the MMC core.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Dave Hylands <dhylands@gmail.com>
Cc: Steve Sakoman <sakoman@gmail.com>
Cc: Chris Ball <cjb@laptop.org>
---
 arch/arm/plat-omap/include/plat/mmc.h |   19 ++++++++++++++++++-
 drivers/mmc/host/omap_hsmmc.c         |    4 ++++
 2 files changed, 22 insertions(+), 1 deletions(-)

diff --git a/arch/arm/plat-omap/include/plat/mmc.h b/arch/arm/plat-omap/include/plat/mmc.h
index c7b8741..94cf70a 100644
--- a/arch/arm/plat-omap/include/plat/mmc.h
+++ b/arch/arm/plat-omap/include/plat/mmc.h
@@ -31,7 +31,24 @@
 
 #define OMAP_MMC_MAX_SLOTS	2
 
-#define OMAP_HSMMC_SUPPORTS_DUAL_VOLT	BIT(1)
+/*
+ * struct omap_mmc_dev_attr.flags possibilities
+ *
+ * OMAP_HSMMC_SUPPORTS_DUAL_VOLT: Some HSMMC controller instances can
+ *    operate with either 1.8Vdc or 3.0Vdc card voltages; this flag
+ *    should be set if this is the case.  See for example Section 22.5.3
+ *    "MMC/SD/SDIO1 Bus Voltage Selection" of the OMAP34xx Multimedia
+ *    Device Silicon Revision 3.1.x Revision ZR (July 2011) (SWPU223R).
+ *
+ * OMAP_HSMMC_BROKEN_MULTIBLOCK_READ: Multiple-block read transfers
+ *    don't work correctly on some MMC controller instances on some
+ *    OMAP3 SoCs; this flag should be set if this is the case.  See
+ *    for example Advisory 2.1.1.128 "MMC: Multiple Block Read
+ *    Operation Issue" in _OMAP3530/3525/3515/3503 Silicon Errata_
+ *    Revision F (October 2010) (SPRZ278F).
+ */
+#define OMAP_HSMMC_SUPPORTS_DUAL_VOLT		BIT(0)
+#define OMAP_HSMMC_BROKEN_MULTIBLOCK_READ	BIT(1)
 
 struct omap_mmc_dev_attr {
 	u8 flags;
diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
index 21e4a79..9e8fc75 100644
--- a/drivers/mmc/host/omap_hsmmc.c
+++ b/drivers/mmc/host/omap_hsmmc.c
@@ -1943,6 +1943,10 @@ static int __init omap_hsmmc_probe(struct platform_device *pdev)
 	omap_hsmmc_context_save(host);
 
 	mmc->caps |= MMC_CAP_DISABLE;
+	if (host->pdata->controller_flags & OMAP_HSMMC_BROKEN_MULTIBLOCK_READ) {
+		dev_info(&pdev->dev, "multiblock reads disabled due to 35xx erratum 2.1.1.128; MMC read performance may suffer\n");
+		mmc->caps |= MMC_CAP_NO_MULTI_READ;
+	}
 
 	pm_runtime_enable(host->dev);
 	pm_runtime_get_sync(host->dev);