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From:   Tobias Schramm <t.schramm@manjaro.org>
To:     Ludovic Desroches <ludovic.desroches@microchip.com>
Cc:     Ulf Hansson <ulf.hansson@linaro.org>,
        Nicolas Ferre <nicolas.ferre@microchip.com>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        Claudiu Beznea <claudiu.beznea@microchip.com>,
        linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org,
        Tobias Schramm <t.schramm@manjaro.org>
Subject: [PATCH 1/1] mmc: atmel-mci: fix race between stop command and start of next command
Date:   Fri, 30 Dec 2022 20:43:15 +0100
Message-Id: <20221230194315.809903-2-t.schramm@manjaro.org>
In-Reply-To: <20221230194315.809903-1-t.schramm@manjaro.org>
References: <20221230194315.809903-1-t.schramm@manjaro.org>
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This commit fixes a race between completion of stop command and start of a
new command.
Previously the command ready interrupt was enabled before stop command
was written to the command register. This caused the command ready
interrupt to fire immediately since the CMDRDY flag is asserted constantly
while there is no command in progress.
Consequently the command state machine will immediately advance to the
next state when the tasklet function is executed again, no matter
actual completion state of the stop command.
Thus a new command can then be dispatched immediately, interrupting and
corrupting the stop command on the CMD line.
Fix that by dropping the command ready interrupt enable before calling
atmci_send_stop_cmd. atmci_send_stop_cmd does already enable the
command ready interrupt, no further writes to ATMCI_IER are necessary.

Signed-off-by: Tobias Schramm <t.schramm@manjaro.org>
---
 drivers/mmc/host/atmel-mci.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/mmc/host/atmel-mci.c b/drivers/mmc/host/atmel-mci.c
index bb9bbf1c927b..dd18440a90c5 100644
--- a/drivers/mmc/host/atmel-mci.c
+++ b/drivers/mmc/host/atmel-mci.c
@@ -1817,7 +1817,6 @@ static void atmci_tasklet_func(struct tasklet_struct *t)
 				atmci_writel(host, ATMCI_IER, ATMCI_NOTBUSY);
 				state = STATE_WAITING_NOTBUSY;
 			} else if (host->mrq->stop) {
-				atmci_writel(host, ATMCI_IER, ATMCI_CMDRDY);
 				atmci_send_stop_cmd(host, data);
 				state = STATE_SENDING_STOP;
 			} else {
@@ -1850,8 +1849,6 @@ static void atmci_tasklet_func(struct tasklet_struct *t)
 				 * command to send.
 				 */
 				if (host->mrq->stop) {
-					atmci_writel(host, ATMCI_IER,
-					             ATMCI_CMDRDY);
 					atmci_send_stop_cmd(host, data);
 					state = STATE_SENDING_STOP;
 				} else {
-- 
2.30.2