linux-kernel - [PATCH 3.16 041/133] skd: Submit requests to firmware before triggering the doorbell

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Message-ID: <lsq.1511315892.801425705@decadent.org.uk>
Date:   Wed, 22 Nov 2017 01:58:12 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Christoph Hellwig" <hch@....de>,
        "Jens Axboe" <axboe@...nel.dk>,
        "Bart Van Assche" <bart.vanassche@....com>,
        "Johannes Thumshirn" <jthumshirn@...e.de>,
        "Hannes Reinecke" <hare@...e.de>
Subject: [PATCH 3.16 041/133] skd: Submit requests to firmware before
 triggering the doorbell

3.16.51-rc1 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: Ben Hutchings <ben@...adent.org.uk>
---
 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);
 }