skd: Submit requests to firmware before triggering the doorbell

BugLink: http://bugs.launchpad.net/bugs/1720154
commit 5fbd545cd3fd311ea1d6e8be4cedddd0ee5684c7 upstream.

Ensure that the members of struct skd_msg_buf have been transferred
to the PCIe adapter before the doorbell is triggered. This patch
avoids that I/O fails sporadically and that the following error
message is reported:

(skd0:STM000196603:[0000:00:09.0]): Completion mismatch comp_id=0x0000 skreq=0x0400 new=0x0000

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>

diff --git a/drivers/block/skd_main.c b/drivers/block/skd_main.c
index edab9c04e8adabc2942b295503d4c950cab82e47..153f20ce318bd52bfbd6140354c1d981eef840e1 100644 (file)
--- a/drivers/block/skd_main.c
+++ b/drivers/block/skd_main.c
@@ -2160,6 +2160,9 @@ static void skd_send_fitmsg(struct skd_device *skdev,
                 */
                qcmd |= FIT_QCMD_MSGSIZE_64;
 
+       /* Make sure skd_msg_buf is written before the doorbell is triggered. */
+       smp_wmb();
+
        SKD_WRITEQ(skdev, qcmd, FIT_Q_COMMAND);
 }
 
@@ -2202,6 +2205,9 @@ static void skd_send_special_fitmsg(struct skd_device *skdev,
        qcmd = skspcl->mb_dma_address;
        qcmd |= FIT_QCMD_QID_NORMAL + FIT_QCMD_MSGSIZE_128;
 
+       /* Make sure skd_msg_buf is written before the doorbell is triggered. */
+       smp_wmb();
+
        SKD_WRITEQ(skdev, qcmd, FIT_Q_COMMAND);
 }