req.sample needs its own cacheline otherwise accessing req.msg fetches
it in again.
Note: This effect doesn't occur if the underlying SPI driver doesn't use
DMA at all.
Signed-off-by: Alexander Stein <alexander.stein@xxxxxxxxxxxxxxxxxxxxx>
---
This obsoletes the patch
[PATCH 1/2] ads7846: Make buffers in ads7846_read12_ser and ads7845_read12_ser DMA save
drivers/input/touchscreen/ads7846.c | 12 ++++++++++--
1 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index c24946f..ab51a8d 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -281,17 +281,25 @@ struct ser_req {
u8 command;
u8 ref_off;
u16 scratch;
- __be16 sample;
struct spi_message msg;
struct spi_transfer xfer[6];
+ /*
+ * DMA (thus cache coherency maintenance) requires the
+ * transfer buffers to live in their own cache lines.
+ */
+ __be16 sample ____cacheline_aligned;
};
struct ads7845_ser_req {
u8 command[3];
u8 pwrdown[3];
- u8 sample[3];
struct spi_message msg;
struct spi_transfer xfer[2];
+ /*
+ * DMA (thus cache coherency maintenance) requires the
+ * transfer buffers to live in their own cache lines.
+ */
+ u8 sample[3] ____cacheline_aligned;
};
static int ads7846_read12_ser(struct device *dev, unsigned command)
--
1.7.3.4
--
To unsubscribe from this list: send the line "unsubscribe linux-input" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
