mmc: atmel-mci: fix race between stop command and start of next command

[ Upstream commit eca5bd6 ]

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 <[email protected]>
Acked-by: Ludovic Desroches <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Ulf Hansson <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>

drivers/mmc/host/atmel-mci.c

@@ -1857,7 +1857,6 @@ static void atmci_tasklet_func(unsigned long priv)
 				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 {
@@ -1890,8 +1889,6 @@ static void atmci_tasklet_func(unsigned long priv)
 				 * 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 {