linux-kernel - [PATCH 4.9 59/88] mmc: sdhci: Do not disable interrupts while waiting for clock

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Message-Id: <20170328122751.096475000@linuxfoundation.org>
Date:   Tue, 28 Mar 2017 14:31:14 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>
Subject: [PATCH 4.9 59/88] mmc: sdhci: Do not disable interrupts while waiting for clock

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

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: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/mmc/host/sdhci.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1371,7 +1371,9 @@ void sdhci_set_clock(struct sdhci_host *
 			return;
 		}
 		timeout--;
-		mdelay(1);
+		spin_unlock_irq(&host->lock);
+		usleep_range(900, 1100);
+		spin_lock_irq(&host->lock);
 	}

 	clk |= SDHCI_CLOCK_CARD_EN;