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From: Faiz Abbas <faiz_abbas@ti.com>
To: <linux-kernel@vger.kernel.org>, <linux-mmc@vger.kernel.org>
Cc: <ulf.hansson@linaro.org>, <asutoshd@codeaurora.org>,
	<riteshh@codeaurora.org>, <adrian.hunter@intel.com>,
	<faiz_abbas@ti.com>
Subject: [RFC] mmc: cqhci: commit descriptors before setting the doorbell
Date: Tue, 15 Oct 2019 00:08:49 +0530	[thread overview]
Message-ID: <20191014183849.14864-1-faiz_abbas@ti.com> (raw)

Add a write memory barrier to make sure that descriptors are actually
written to memory before ringing the doorbell.

Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
---

This patch fixes a very infrequent ADMA error (1 out of 100 times) that
I have been seeing after enabling command queuing for J721e.
Also looking at memory-barriers.txt and this commit[1],
it looks like we should be doing this before any descriptor write
followed by a doorbell ring operation. It'll be nice if someone with more
expertise in memory barriers can comment.

[1] ad1a1b9cd67a ("scsi: ufs: commit descriptors before setting the
    doorbell")

 drivers/mmc/host/cqhci.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/cqhci.c b/drivers/mmc/host/cqhci.c
index f7bdae5354c3..5047f7343ffc 100644
--- a/drivers/mmc/host/cqhci.c
+++ b/drivers/mmc/host/cqhci.c
@@ -611,7 +611,8 @@ static int cqhci_request(struct mmc_host *mmc, struct mmc_request *mrq)
 	cq_host->slot[tag].flags = 0;
 
 	cq_host->qcnt += 1;
-
+	/* Make sure descriptors are ready before ringing the doorbell */
+	wmb();
 	cqhci_writel(cq_host, 1 << tag, CQHCI_TDBR);
 	if (!(cqhci_readl(cq_host, CQHCI_TDBR) & (1 << tag)))
 		pr_debug("%s: cqhci: doorbell not set for tag %d\n",
-- 
2.19.2


WARNING: multiple messages have this Message-ID (diff)
From: Faiz Abbas <faiz_abbas@ti.com>
To: linux-kernel@vger.kernel.org, linux-mmc@vger.kernel.org
Cc: ulf.hansson@linaro.org, asutoshd@codeaurora.org,
	riteshh@codeaurora.org, adrian.hunter@intel.com,
	faiz_abbas@ti.com
Subject: [RFC] mmc: cqhci: commit descriptors before setting the doorbell
Date: Tue, 15 Oct 2019 00:08:49 +0530	[thread overview]
Message-ID: <20191014183849.14864-1-faiz_abbas@ti.com> (raw)

Add a write memory barrier to make sure that descriptors are actually
written to memory before ringing the doorbell.

Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
---

This patch fixes a very infrequent ADMA error (1 out of 100 times) that
I have been seeing after enabling command queuing for J721e.
Also looking at memory-barriers.txt and this commit[1],
it looks like we should be doing this before any descriptor write
followed by a doorbell ring operation. It'll be nice if someone with more
expertise in memory barriers can comment.

[1] ad1a1b9cd67a ("scsi: ufs: commit descriptors before setting the
    doorbell")

 drivers/mmc/host/cqhci.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/cqhci.c b/drivers/mmc/host/cqhci.c
index f7bdae5354c3..5047f7343ffc 100644
--- a/drivers/mmc/host/cqhci.c
+++ b/drivers/mmc/host/cqhci.c
@@ -611,7 +611,8 @@ static int cqhci_request(struct mmc_host *mmc, struct mmc_request *mrq)
 	cq_host->slot[tag].flags = 0;
 
 	cq_host->qcnt += 1;
-
+	/* Make sure descriptors are ready before ringing the doorbell */
+	wmb();
 	cqhci_writel(cq_host, 1 << tag, CQHCI_TDBR);
 	if (!(cqhci_readl(cq_host, CQHCI_TDBR) & (1 << tag)))
 		pr_debug("%s: cqhci: doorbell not set for tag %d\n",
-- 
2.19.2

             reply	other threads:[~2019-10-14 18:38 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-14 18:38 Faiz Abbas [this message]
2019-10-14 18:38 ` [RFC] mmc: cqhci: commit descriptors before setting the doorbell Faiz Abbas
2019-10-15  7:55 ` Faiz Abbas
2019-10-15  7:55   ` Faiz Abbas
2019-10-15 13:45   ` Adrian Hunter
2019-10-16 12:16     ` Faiz Abbas
2019-10-16 12:16       ` Faiz Abbas
2019-10-18  7:22       ` Faiz Abbas
2019-10-18  7:22         ` Faiz Abbas
2019-10-18  7:30         ` Adrian Hunter
2019-10-18 10:58 ` Ulf Hansson
2019-10-18 11:27   ` Faiz Abbas

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