linux-kernel - [PATCH 3.18 17/42] skd: Submit requests to firmware before triggering the doorbell

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Date:   Sun, 24 Sep 2017 22:27:52 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Bart Van Assche <bart.vanassche@....com>,
        Christoph Hellwig <hch@....de>, Hannes Reinecke <hare@...e.de>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 3.18 17/42] skd: Submit requests to firmware before triggering the doorbell

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bart Van Assche <bart.vanassche@....com>

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@....com>
Cc: Christoph Hellwig <hch@....de>
Cc: Hannes Reinecke <hare@...e.de>
Cc: Johannes Thumshirn <jthumshirn@...e.de>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/block/skd_main.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/block/skd_main.c
+++ b/drivers/block/skd_main.c
@@ -2214,6 +2214,9 @@ static void skd_send_fitmsg(struct skd_d
 		 */
 		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);
 
 }
@@ -2260,6 +2263,9 @@ static void skd_send_special_fitmsg(stru
 	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);
 }