Messages in this thread Patch in this message | | | Date | Wed, 11 Apr 2012 16:13:43 -0700 | From | Greg KH <> | Subject | [ 36/42] mfd: Clear twl6030 IRQ status register only once |
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3.0-stable review patch. If anyone has any objections, please let me know.
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From: Nishanth Menon <nm@ti.com>
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 <santosh.shilimkar@ti.com> Signed-off-by: Nishanth Menon <nm@ti.com> Signed-off-by: Samuel Ortiz <sameo@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/mfd/twl6030-irq.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)
--- a/drivers/mfd/twl6030-irq.c +++ b/drivers/mfd/twl6030-irq.c @@ -145,8 +145,17 @@ 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");
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