linux-omap2 git: add patch to fix a race in i2c code

2 files changed, 120 insertions, 1 deletions

diff --git a/packages/linux/linux-omap2-git/beagleboard/i2c-omap-race-fix.diff b/packages/linux/linux-omap2-git/beagleboard/i2c-omap-race-fix.diff
new file mode 100644
index 0000000000..6eb33f76b7
--- /dev/null
+++ b/packages/linux/linux-omap2-git/beagleboard/i2c-omap-race-fix.diff
@@ -0,0 +1,118 @@
+From linux-omap-owner@vger.kernel.org Tue Jul 15 21:23:13 2008
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+Date: 	Tue, 15 Jul 2008 13:00:18 -0600 (MDT)
+From: Paul Walmsley <paul@pwsan.com>
+To: linux-omap@vger.kernel.org
+Subject: [PATCH] i2c-omap: close suspected race between omap_i2c_idle() and
+ omap_i2c_isr()
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+
+
+omap_i2c_idle() sets an internal flag, "dev->idle", instructing its
+ISR to decline interrupts.  It sets this flag before it actually masks
+the interrupts on the I2C controller.  This is problematic, since an
+I2C interrupt could arrive after dev->idle is set, but before the
+interrupt source is masked.  When this happens, Linux disables the I2C
+controller's IRQ, causing all future transactions on the bus to fail.
+
+Symptoms, happening on about 7% of boots:
+
+   irq 56: nobody cared (try booting with the "irqpoll" option)
+   <warning traceback here>
+   Disabling IRQ #56
+   i2c_omap i2c_omap.1: controller timed out
+
+In omap_i2c_idle(), this patch sets dev->idle only after the interrupt
+mask write to the I2C controller has left the ARM write buffer.
+That's probably the major offender.  For additional prophylaxis, in
+omap_i2c_unidle(), the patch clears the dev->idle flag before
+interrupts are enabled, rather than afterwards.
+
+The patch has survived twenty-two reboots on the 3430SDP here without
+wedging I2C1.  Not absolutely dispositive, but promising!
+
+
+Signed-off-by: Paul Walmsley <paul@pwsan.com>
+---
+
+ drivers/i2c/busses/i2c-omap.c |   10 ++++++++--
+ 1 files changed, 8 insertions(+), 2 deletions(-)
+
+diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
+index 55779f5..ed7e9ad 100644
+--- a/drivers/i2c/busses/i2c-omap.c
++++ b/drivers/i2c/busses/i2c-omap.c
+@@ -209,22 +209,28 @@ static void omap_i2c_unidle(struct omap_i2c_dev *dev)
+ 	if (dev->iclk != NULL)
+ 		clk_enable(dev->iclk);
+ 	clk_enable(dev->fclk);
++	dev->idle = 0;
+ 	if (dev->iestate)
+ 		omap_i2c_write_reg(dev, OMAP_I2C_IE_REG, dev->iestate);
+-	dev->idle = 0;
+ }
+ 
+ static void omap_i2c_idle(struct omap_i2c_dev *dev)
+ {
+ 	u16 iv;
+ 
+-	dev->idle = 1;
+ 	dev->iestate = omap_i2c_read_reg(dev, OMAP_I2C_IE_REG);
+ 	omap_i2c_write_reg(dev, OMAP_I2C_IE_REG, 0);
+ 	if (dev->rev1)
+ 		iv = omap_i2c_read_reg(dev, OMAP_I2C_IV_REG);
+ 	else
+ 		omap_i2c_write_reg(dev, OMAP_I2C_STAT_REG, dev->iestate);
++	/*
++	 * The wmb() is to ensure that the I2C interrupt mask write
++	 * reaches the I2C controller before the dev->idle store
++	 * occurs.
++	 */
++	wmb();
++	dev->idle = 1;
+ 	clk_disable(dev->fclk);
+ 	if (dev->iclk != NULL)
+ 		clk_disable(dev->iclk);
+--
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diff --git a/packages/linux/linux-omap2_git.bb b/packages/linux/linux-omap2_git.bb
index 53bcd297d9..800a0eb02e 100644
--- a/packages/linux/linux-omap2_git.bb
+++ b/packages/linux/linux-omap2_git.bb
@@ -5,7 +5,7 @@ FILESDIR = "${@os.path.dirname(bb.data.getVar('FILE',d,1))}/linux-omap2-git/${MA
 SRCREV = "7786cd7a00ae0b18923185789380a88052f4eee7"
 
 PV = "2.6.25+2.6.26-rc9+${PR}+git${SRCREV}"
-PR = "r44"
+PR = "r45"
 
 SRC_URI = "git://source.mvista.com/git/linux-omap-2.6.git;protocol=git \
 	   file://defconfig"
@@ -30,6 +30,7 @@ SRC_URI_append_beagleboard = " file://no-harry-potter.diff;patch=1 \
            file://07-set-burst-size.diff;patch=1 \
            file://cache-display-fix.patch;patch=1 \
            file://serialfix.diff;patch=1 \
+           file://i2c-omap-race-fix.diff;patch=1 \
 "
 
 SRC_URI_append_omap3evm = " file://no-harry-potter.diff;patch=1 \