[PATCH v2] i2c: omap: Fix standard mode false ACK readings

[PATCH v2] i2c: omap: Fix standard mode false ACK readings

[Reid Tonking]

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>
---
 drivers/i2c/busses/i2c-omap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index 2b4e2be51318..4199f57a6bf2 100644
--- 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;
-- 
2.34.1

Re: [PATCH v2] i2c: omap: Fix standard mode false ACK readings

[Wolfram Sang]

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On Wed, Apr 26, 2023 at 02:49:56PM -0500, Reid Tonking wrote:
> 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>

Applied to for-current, thanks!


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