linux-kernel - [PATCH 3.10 200/268] mmc: sdhci: Do not disable interrupts while waiting for clock

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Date:   Mon, 19 Jun 2017 20:31:39 +0200
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Jiri Slaby <jslaby@...e.cz>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 200/268] mmc: sdhci: Do not disable interrupts while waiting for clock

From: Adrian Hunter <adrian.hunter@...el.com>

commit e2ebfb2142acefecc2496e71360f50d25726040b upstream.

Disabling interrupts for even a millisecond can cause problems for some
devices. That can happen when sdhci changes clock frequency because it
waits for the clock to become stable under a spin lock.

The spin lock is not necessary here. Anything that is racing with changes
to the I/O state is already broken. The mmc core already provides
synchronization via "claiming" the host.

Although the spin lock probably should be removed from the code paths that
lead to this point, such a patch would touch too much code to be suitable
for stable trees. Consequently, for this patch, just drop the spin lock
while waiting.

Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
Tested-by: Ludovic Desroches <ludovic.desroches@...rochip.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
Signed-off-by: Willy Tarreau <w@....eu>
---
 drivers/mmc/host/sdhci.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 836e2ac..16d7f93 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1220,7 +1220,9 @@ clock_set:
 			return;
 		}
 		timeout--;
-		mdelay(1);
+		spin_unlock_irq(&host->lock);
+		usleep_range(900, 1100);
+		spin_lock_irq(&host->lock);
 	}

 	clk |= SDHCI_CLOCK_CARD_EN;
-- 
2.8.0.rc2.1.gbe9624a