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From:   Arun Kumar Neelakantam <aneela@codeaurora.org>
To:     bjorn.andersson@linaro.org, clew@codeaurora.org
Cc:     Arun Kumar Neelakantam <aneela@codeaurora.org>,
        Andy Gross <agross@kernel.org>,
        linux-arm-msm@vger.kernel.org (open list:ARM/QUALCOMM SUPPORT),
        linux-kernel@vger.kernel.org (open list)
Subject: [PATCH] soc: qcom: aoss: Read back before triggering the IRQ
Date:   Wed, 22 Jan 2020 13:54:13 +0530
Message-Id: <1579681454-1229-1-git-send-email-aneela@codeaurora.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

In some device memory used by msm_qmp, there can be an early ack of a
write to memory succeeding. This may cause the outgoing interrupt to be
triggered before the msgram reflects the write.

Add a readback to ensure the data is flushed to device memory before
triggering the ipc interrupt.

Signed-off-by: Arun Kumar Neelakantam <aneela@codeaurora.org>
---
 drivers/soc/qcom/qcom_aoss.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/soc/qcom/qcom_aoss.c b/drivers/soc/qcom/qcom_aoss.c
index fe79661..f43a2e0 100644
--- a/drivers/soc/qcom/qcom_aoss.c
+++ b/drivers/soc/qcom/qcom_aoss.c
@@ -225,6 +225,7 @@ static bool qmp_message_empty(struct qmp *qmp)
 static int qmp_send(struct qmp *qmp, const void *data, size_t len)
 {
 	long time_left;
+	size_t tlen;
 	int ret;
 
 	if (WARN_ON(len + sizeof(u32) > qmp->size))
@@ -239,6 +240,9 @@ static int qmp_send(struct qmp *qmp, const void *data, size_t len)
 	__iowrite32_copy(qmp->msgram + qmp->offset + sizeof(u32),
 			 data, len / sizeof(u32));
 	writel(len, qmp->msgram + qmp->offset);
+
+	/* Read back len to confirm data written in message RAM */
+	tlen = readl(qmp->msgram + qmp->offset);
 	qmp_kick(qmp);
 
 	time_left = wait_event_interruptible_timeout(qmp->event,
-- 
1.9.1