i2c: mpc: Poll for MCF

During some transfers the bus can still be busy when an interrupt is received. Commit 763778c ("i2c: mpc: Restore reread of I2C status register") attempted to address this by re-reading MPC_I2C_SR once but that just made it less likely to happen without actually preventing it. Instead of a single re-read, poll with a timeout so that the bus is given enough time to settle but a genuine stuck SCL is still noticed. Fixes: 1538d82 ("i2c: mpc: Interrupt driven transfer") Signed-off-by: Chris Packham <[email protected]> Signed-off-by: Wolfram Sang <[email protected]>
jix · Jul 20, 2021 · 4a8ac5e · 4a8ac5e
1 parent a750bff
commit 4a8ac5e
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
@@ -635,8 +635,8 @@ static irqreturn_t mpc_i2c_isr(int irq, void *dev_id)
 
 	status = readb(i2c->base + MPC_I2C_SR);
 	if (status & CSR_MIF) {
-		/* Read again to allow register to stabilise */
-		status = readb(i2c->base + MPC_I2C_SR);
+		/* Wait up to 100us for transfer to properly complete */
+		readb_poll_timeout(i2c->base + MPC_I2C_SR, status, !(status & CSR_MCF), 0, 100);
 		writeb(0, i2c->base + MPC_I2C_SR);
 		mpc_i2c_do_intr(i2c, status);
 		return IRQ_HANDLED;