1 files changed, 118 insertions, 0 deletions

diff --git a/meta/recipes-kernel/linux/linux-omap2-git/beagleboard/i2c-omap-race-fix.diff b/meta/recipes-kernel/linux/linux-omap2-git/beagleboard/i2c-omap-race-fix.diff
new file mode 100644
index 0000000000..6eb33f76b7
--- /dev/null
+++ b/meta/recipes-kernel/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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