i2c: omap: Fix standard mode false ACK readings

commit c770657bd2611b077ec1e7b1fe6aa92f249399bd upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index a03564f41ad0a231a6bc16df3d6107053f10a7b9..68b35220d2625dea60a767fc526ebb9775cdb2d1 100644 (file)
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -1030,7 +1030,7 @@ 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;