i2c: mpc: Poll for MCF

During some transfers the bus can still be busy when an interrupt is
received. Commit 763778cd7926 ("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: 1538d82f4647 ("i2c: mpc: Interrupt driven transfer")
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
index 6d5014e..a6ea1eb 100644 (file)
--- 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;