i2c: omap: Fix standard mode false ACK readings

Using standard mode, rare false ACK responses were appearing with
i2cdetect tool. This was happening due to NACK interrupt triggering
ISR thread before register access interrupt was ready. Removing the
NACK interrupt's ability to trigger ISR thread lets register access
ready interrupt do this instead.

Cc: <stable@vger.kernel.org> # v3.7+
Fixes: 3b2f8f82dad7 ("i2c: omap: switch to threaded IRQ support")
Signed-off-by: Reid Tonking <reidt@ti.com>
Acked-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index 2b4e2be51318f8695dcb89a0b30d9fb78d50c194..4199f57a6bf299b142d5344a1a916fca2197b26d 100644 (file)
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -1058,7 +1058,7 @@ omap_i2c_isr(int irq, void *dev_id)
        u16 stat;
 
        stat = omap_i2c_read_reg(omap, OMAP_I2C_STAT_REG);
-       mask = omap_i2c_read_reg(omap, OMAP_I2C_IE_REG);
+       mask = omap_i2c_read_reg(omap, OMAP_I2C_IE_REG) & ~OMAP_I2C_STAT_NACK;
 
        if (stat & mask)
                ret = IRQ_WAKE_THREAD;