From: Nishanth Menon Date: Thu, 23 Feb 2012 02:03:45 +0000 (-0600) Subject: mfd: Clear twl6030 IRQ status register only once X-Git-Url: http://git.alex.org.uk mfd: Clear twl6030 IRQ status register only once BugLink: http://bugs.launchpad.net/bugs/981162 commit 3f8349e6e98ba0455437724589072523865eae5e upstream. TWL6030 family of PMIC use a shadow interrupt status register while kernel processes the current interrupt event. However, any write(0 or 1) to register INT_STS_A, INT_STS_B or INT_STS_C clears all 3 interrupt status registers. Since clear of the interrupt is done on 32k clk, depending on I2C bus speed, we could in-adverently clear the status of a interrupt status pending on shadow register in the current implementation. This is due to the fact that multi-byte i2c write operation into three seperate status register could result in multiple load and clear of status and result in lost interrupts. Instead, doing a single byte write to INT_STS_A register with 0x0 will clear all three interrupt status registers without the related risk. Acked-by: Santosh Shilimkar Signed-off-by: Nishanth Menon Signed-off-by: Samuel Ortiz Signed-off-by: Greg Kroah-Hartman Signed-off-by: Leann Ogasawara Signed-off-by: Tim Gardner --- diff --git a/drivers/mfd/twl6030-irq.c b/drivers/mfd/twl6030-irq.c index 3eee45f..83f4988 100644 --- a/drivers/mfd/twl6030-irq.c +++ b/drivers/mfd/twl6030-irq.c @@ -187,8 +187,17 @@ static int twl6030_irq_thread(void *data) } local_irq_enable(); } - ret = twl_i2c_write(TWL_MODULE_PIH, sts.bytes, - REG_INT_STS_A, 3); /* clear INT_STS_A */ + + /* + * NOTE: + * Simulation confirms that documentation is wrong w.r.t the + * interrupt status clear operation. A single *byte* write to + * any one of STS_A to STS_C register results in all three + * STS registers being reset. Since it does not matter which + * value is written, all three registers are cleared on a + * single byte write, so we just use 0x0 to clear. + */ + ret = twl_i2c_write_u8(TWL_MODULE_PIH, 0x00, REG_INT_STS_A); if (ret) pr_warning("twl6030: I2C error in clearing PIH ISR\n");