i2cdetect scanned i2c bus slow because the i2c-mxs driver ignored
the NO_SLAVE_ACK bit during busy-waiting loop.
Thanks to the patch, the speedup happens.
The change doesn't break anything else because:
- on SELECT: NO_SLAVE_ACK bit checking is just welcome
- on READ: master (the i2c controller, no slave device) generates
ACK/NAK bit
- on WRITE: NO_SLAVE_ACK can be treated as NAK (the same effect)
so even the i2c controller sets NO_SLAVE_ACK on NAK (not confirmed)
the WRITE is not effected
- on clock stretching: SCL wire is involved, it has no influence
on the ACK bit value on SDA wire
Signed-off-by: Janusz Uzycki <j.uzycki@xxxxxxxxxxxxxx>
---
drivers/i2c/busses/i2c-mxs.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/i2c/busses/i2c-mxs.c b/drivers/i2c/busses/i2c-mxs.c
index 87ee72d..f3c4a43 100644
--- a/drivers/i2c/busses/i2c-mxs.c
+++ b/drivers/i2c/busses/i2c-mxs.c
@@ -307,6 +307,9 @@ static int mxs_i2c_pio_wait_xfer_end(struct mxs_i2c_dev *i2c)
unsigned long timeout = jiffies + msecs_to_jiffies(1000);
while (readl(i2c->regs + MXS_I2C_CTRL0) & MXS_I2C_CTRL0_RUN) {
+ if (readl(i2c->regs + MXS_I2C_CTRL1) &
+ MXS_I2C_CTRL1_NO_SLAVE_ACK_IRQ)
+ return -ENXIO;
if (time_after(jiffies, timeout))
return -ETIMEDOUT;
cond_resched();
--
1.7.11.3
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