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[5.13,779/800] i2c: mpc: Restore reread of I2C status register

Message ID 20210712061049.723306779@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg KH July 12, 2021, 6:13 a.m. UTC 
From: Chris Packham <chris.packham@alliedtelesis.co.nz>

[ Upstream commit 763778cd79267dadf0ec7e044caf7563df0ab597 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/i2c/busses/i2c-mpc.c | 2 ++
 1 file changed, 2 insertions(+)
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Patch

diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
index dcca9c2396db..6d5014ebaab5 100644
--- a/drivers/i2c/busses/i2c-mpc.c
+++ b/drivers/i2c/busses/i2c-mpc.c
@@ -635,6 +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);
 		writeb(0, i2c->base + MPC_I2C_SR);
 		mpc_i2c_do_intr(i2c, status);
 		return IRQ_HANDLED;