i2c: mpc: Restore reread of I2C status register

Prior to commit 1538d82f4647 ("i2c: mpc: Interrupt driven transfer") the
old interrupt handler would reread MPC_I2C_SR after checking the CSR_MIF
bit. When the driver was re-written this was removed as it seemed
unnecessary. However as it turns out this is necessary for i2c devices
which do clock stretching otherwise we end up thinking the bus is still
busy when processing the interrupt.

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 30d9e89a3db20a9f83dc120beb504de93b1ffc1a..2ee4a9361e4046843c44ac4f92a80f62a5afb823 100644 (file)
--- a/drivers/i2c/busses/i2c-mpc.c
+++ b/drivers/i2c/busses/i2c-mpc.c
@@ -564,6 +564,8 @@ 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);
                writeb(0, i2c->base + MPC_I2C_SR);
                mpc_i2c_do_intr(i2c, status);
                return IRQ_HANDLED;