[PATCH AUTOSEL 5.4 09/14] i2c: mv64xxx: Fix random system lock caused by runtime PM

From: Sasha Levin
Date: Mon Apr 19 2021 - 16:48:30 EST

From: Marek Behún <kabel@xxxxxxxxxx>

[ Upstream commit 39930213e7779b9c4257499972b8afb8858f1a2d ]

I noticed a weird bug with this driver on Marvell CN9130 Customer
Reference Board.

Sometime after boot, the system locks with the following message:
[104.071363] i2c i2c-0: mv64xxx: I2C bus locked, block: 1, time_left: 0

The system does not respond afterwards, only warns about RCU stalls.

This first appeared with commit e5c02cf54154 ("i2c: mv64xxx: Add runtime
PM support").

With further experimentation I discovered that adding a delay into
mv64xxx_i2c_hw_init() fixes this issue. This function is called before
every xfer, due to how runtime PM works in this driver. It seems that in
order to work correctly, a delay is needed after the bus is reset in
this function.

Since there already is a known erratum with this controller needing a
delay, I assume that this is just another place this needs to be
applied. Therefore I apply the delay only if errata_delay is true.

Signed-off-by: Marek Behún <kabel@xxxxxxxxxx>
Acked-by: Gregory CLEMENT <gregory.clement@xxxxxxxxxxx>
Reviewed-by: Samuel Holland <samuel@xxxxxxxxxxxx>
Signed-off-by: Wolfram Sang <wsa@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/i2c/busses/i2c-mv64xxx.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/i2c/busses/i2c-mv64xxx.c b/drivers/i2c/busses/i2c-mv64xxx.c
index a5a95ea5b81a..7409cfba2195 100644
--- a/drivers/i2c/busses/i2c-mv64xxx.c
+++ b/drivers/i2c/busses/i2c-mv64xxx.c
@@ -218,6 +218,10 @@ mv64xxx_i2c_hw_init(struct mv64xxx_i2c_data *drv_data)
writel(0, drv_data->reg_base + drv_data->reg_offsets.ext_addr);
drv_data->reg_base + drv_data->reg_offsets.control);
+ if (drv_data->errata_delay)
+ udelay(5);
drv_data->state = MV64XXX_I2C_STATE_IDLE;