From 0cbbcffdf5f30ef60d918549014684eada4f5b3f Mon Sep 17 00:00:00 2001 From: Paul Walmsley Date: Fri, 21 Nov 2008 13:39:45 -0800 Subject: i2c-omap: Close suspected race between omap_i2c_idle() and omap_i2c_isr() 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) 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 Signed-off-by: Tony Lindgren --- drivers/i2c/busses/i2c-omap.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c index 17476ecd978..5ca0e0010a0 100644 --- a/drivers/i2c/busses/i2c-omap.c +++ b/drivers/i2c/busses/i2c-omap.c @@ -181,22 +181,26 @@ 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) + if (dev->rev1) { iv = omap_i2c_read_reg(dev, OMAP_I2C_IV_REG); /* Read clears */ - else + } else { omap_i2c_write_reg(dev, OMAP_I2C_STAT_REG, dev->iestate); + + /* Flush posted write before the dev->idle store occurs */ + omap_i2c_read_reg(dev, OMAP_I2C_STAT_REG); + } + dev->idle = 1; clk_disable(dev->fclk); if (dev->iclk != NULL) clk_disable(dev->iclk); -- cgit v1.2.3