6.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Tan En De ende.tan@starfivetech.com
[ Upstream commit 2fe2b969d911a09abcd6a47401a3c66c38a310e6 ]
Replaced pm_runtime_put() with pm_runtime_put_sync_suspend() to ensure the runtime suspend is invoked immediately when unregistering a slave. This prevents a race condition where suspend was skipped when unregistering and registering slave in quick succession.
For example, consider the rapid sequence of `delete_device -> new_device -> delete_device -> new_device`. In this sequence, it is observed that the dw_i2c_plat_runtime_suspend() might not be invoked after `delete_device` operation.
This is because after `delete_device` operation, when the pm_runtime_put() is about to trigger suspend, the following `new_device` operation might race and cancel the suspend.
If that happens, during the `new_device` operation, dw_i2c_plat_runtime_resume() is skipped (since there was no suspend), which means `i_dev->init()`, i.e. i2c_dw_init_slave(), is skipped. Since i2c_dw_init_slave() is skipped, i2c_dw_configure_fifo_slave() is skipped too, which leaves `DW_IC_INTR_MASK` unconfigured. If we inspect the interrupt mask register using devmem, it will show as zero.
Example shell script to reproduce the issue: ``` #!/bin/sh
SLAVE_LADDR=0x1010 SLAVE_BUS=13 NEW_DEVICE=/sys/bus/i2c/devices/i2c-$SLAVE_BUS/new_device DELETE_DEVICE=/sys/bus/i2c/devices/i2c-$SLAVE_BUS/delete_device
# Create initial device echo slave-24c02 $SLAVE_LADDR > $NEW_DEVICE sleep 2
# Rapid sequence of # delete_device -> new_device -> delete_device -> new_device echo $SLAVE_LADDR > $DELETE_DEVICE echo slave-24c02 $SLAVE_LADDR > $NEW_DEVICE echo $SLAVE_LADDR > $DELETE_DEVICE echo slave-24c02 $SLAVE_LADDR > $NEW_DEVICE
# Using devmem to inspect IC_INTR_MASK will show as zero ```
Signed-off-by: Tan En De ende.tan@starfivetech.com Acked-by: Jarkko Nikula jarkko.nikula@linux.intel.com Link: https://lore.kernel.org/r/20250412023303.378600-1-ende.tan@starfivetech.com Signed-off-by: Andi Shyti andi.shyti@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/i2c/busses/i2c-designware-slave.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/i2c/busses/i2c-designware-slave.c b/drivers/i2c/busses/i2c-designware-slave.c index 5cd4a5f7a472e..b936a240db0a9 100644 --- a/drivers/i2c/busses/i2c-designware-slave.c +++ b/drivers/i2c/busses/i2c-designware-slave.c @@ -96,7 +96,7 @@ static int i2c_dw_unreg_slave(struct i2c_client *slave) i2c_dw_disable(dev); synchronize_irq(dev->irq); dev->slave = NULL; - pm_runtime_put(dev->dev); + pm_runtime_put_sync_suspend(dev->dev);
return 0; }