dw_spi: Fix missing final read in some polling situations

There is a possibility that the last word of a transaction will be lost
if data is not ready.  Re-read in poll_transfer() to solve this issue
when poll_mode is enabled.

Verified on SPI touch screen device.

Signed-off-by: Major Lee <major_lee@wistron.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/spi/dw_spi.c b/drivers/spi/dw_spi.c
index 90439314cf67..0838c79861e4 100644
--- a/drivers/spi/dw_spi.c
+++ b/drivers/spi/dw_spi.c
@@ -413,6 +413,11 @@ static void poll_transfer(struct dw_spi *dws)
 {
         while (dws->write(dws))
                 dws->read(dws);
+        /*
+         * There is a possibility that the last word of a transaction
+         * will be lost if data is not ready. Re-read to solve this issue.
+         */
+        dws->read(dws);
 
         transfer_complete(dws);
 }