[PATCH review for 3.18 22/30] mmc: sdio: fix alignment issue in struct sdio_func

[Levin, Alexander (Sasha Levin)]

From: Heiner Kallweit <hkallweit1@xxxxxxxxx>

[ Upstream commit 5ef1ecf060f28ecef313b5723f1fd39bf5a35f56 ]

Certain 64-bit systems (e.g. Amlogic Meson GX) require buffers to be
used for DMA to be 8-byte-aligned. struct sdio_func has an embedded
small DMA buffer not meeting this requirement.
When testing switching to descriptor chain mode in meson-gx driver
SDIO is broken therefore. Fix this by allocating the small DMA buffer
separately as kmalloc ensures that the returned memory area is
properly aligned for every basic data type.

Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
Tested-by: Helmut Klein <hgkr.klein@xxxxxxxxx>
Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
---
 drivers/mmc/core/sdio_bus.c   | 12 +++++++++++-
 include/linux/mmc/sdio_func.h |  2 +-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/core/sdio_bus.c b/drivers/mmc/core/sdio_bus.c
index 6da97b170563..8d246f815658 100644
--- a/drivers/mmc/core/sdio_bus.c
+++ b/drivers/mmc/core/sdio_bus.c
@@ -265,7 +265,7 @@ static void sdio_release_func(struct device *dev)
 	sdio_free_func_cis(func);
 
 	kfree(func->info);
-
+	kfree(func->tmpbuf);
 	kfree(func);
 }
 
@@ -280,6 +280,16 @@ struct sdio_func *sdio_alloc_func(struct mmc_card *card)
 	if (!func)
 		return ERR_PTR(-ENOMEM);
 
+	/*
+	 * allocate buffer separately to make sure it's properly aligned for
+	 * DMA usage (incl. 64 bit DMA)
+	 */
+	func->tmpbuf = kmalloc(4, GFP_KERNEL);
+	if (!func->tmpbuf) {
+		kfree(func);
+		return ERR_PTR(-ENOMEM);
+	}
+
 	func->card = card;
 
 	device_initialize(&func->dev);
diff --git a/include/linux/mmc/sdio_func.h b/include/linux/mmc/sdio_func.h
index 50f0bc952328..2d6cc69db1fe 100644
--- a/include/linux/mmc/sdio_func.h
+++ b/include/linux/mmc/sdio_func.h
@@ -53,7 +53,7 @@ struct sdio_func {
 	unsigned int		state;		/* function state */
 #define SDIO_STATE_PRESENT	(1<<0)		/* present in sysfs */
 
-	u8			tmpbuf[4];	/* DMA:able scratch buffer */
+	u8			*tmpbuf;	/* DMA:able scratch buffer */
 
 	unsigned		num_info;	/* number of info strings */
 	const char		**info;		/* info strings */
-- 
2.11.0