linux-kernel - [34-longterm 067/260] tmio_mmc: don't clear unhandled pending interrupts

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Date:	Sun,  2 Jan 2011 02:16:03 -0500
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	stable@...nel.org, linux-kernel@...r.kernel.org
Cc:	stable-review@...nel.org, Yusuke Goda <yusuke.goda.sx@...esas.com>,
	Matt Fleming <matt@...sole-pimps.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Paul Mundt <lethal@...ux-sh.org>, <linux-mmc@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [34-longterm 067/260] tmio_mmc: don't clear unhandled pending interrupts

From: Yusuke Goda <yusuke.goda.sx@...esas.com>

commit b78d6c5f51935ba89df8db33a57bacb547aa7325 upstream.

Previously, it was possible for ack_mmc_irqs() to clear pending interrupt
bits in the CTL_STATUS register, even though the interrupt handler had not
been called.  This was because of a race that existed when doing a
read-modify-write sequence on CTL_STATUS.  After the read step in this
sequence, if an interrupt occurred (causing one of the bits in CTL_STATUS
to be set) the write step would inadvertently clear it.

Observed with the TMIO_STAT_RXRDY bit together with CMD53 on AR6002 and
BCM4318 SDIO cards in polled mode.

This patch eliminates this race by only writing to CTL_STATUS and clearing
the interrupts that were passed as an argument to ack_mmc_irqs()."

[matt@...sole-pimps.org: rewrote changelog]
Signed-off-by: Yusuke Goda <yusuke.goda.sx@...esas.com>
Acked-by: Magnus Damm <damm@...nsource.se>"
Tested-by: Arnd Hannemann <arnd@...dnet.de>"
Acked-by: Ian Molton <ian@...menth.co.uk>
Cc: Matt Fleming <matt@...sole-pimps.org>
Cc: Samuel Ortiz <sameo@...ux.intel.com>
Cc: Paul Mundt <lethal@...ux-sh.org>
Cc: <linux-mmc@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>

Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 drivers/mmc/host/tmio_mmc.h |    5 +----
 1 files changed, 1 insertions(+), 4 deletions(-)

diff --git a/drivers/mmc/host/tmio_mmc.h b/drivers/mmc/host/tmio_mmc.h
index dafecfb..1836ed9 100644
--- a/drivers/mmc/host/tmio_mmc.h
+++ b/drivers/mmc/host/tmio_mmc.h
@@ -80,10 +80,7 @@
 
 #define ack_mmc_irqs(host, i) \
 	do { \
-		u32 mask;\
-		mask  = sd_ctrl_read32((host), CTL_STATUS); \
-		mask &= ~((i) & TMIO_MASK_IRQ); \
-		sd_ctrl_write32((host), CTL_STATUS, mask); \
+		sd_ctrl_write32((host), CTL_STATUS, ~(i)); \
 	} while (0)
 
 
-- 
1.7.3.3

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