[ Upstream commit f6c29f710c1ff2590109f83be3e212b86c01e0f3 ]
If a SMBus alert is received and the originating device is not found,
the reason may be that the address reported on the SMBus alert address
is corrupted, for example because multiple devices asserted alert and
do not correctly implement SMBus arbitration.
If this happens, call alert handlers on all devices connected to the
given I2C bus, in the hope that this cleans up the situation.
This change reliably fixed the problem on a system with multiple devices
on a single bus. Example log where the device on address 0x18 (ADM1021)
and on address 0x4c (ADT7461A) both had the alert line asserted:
smbus_alert 3-000c: SMBALERT# from dev 0x0c, flag 0
smbus_alert 3-000c: no driver alert()!
smbus_alert 3-000c: SMBALERT# from dev 0x0c, flag 0
smbus_alert 3-000c: no driver alert()!
lm90 3-0018: temp1 out of range, please check!
lm90 3-0018: Disabling ALERT#
lm90 3-0029: Everything OK
lm90 3-002a: Everything OK
lm90 3-004c: temp1 out of range, please check!
lm90 3-004c: temp2 out of range, please check!
lm90 3-004c: Disabling ALERT#
Fixes: b5527a7766f0 ("i2c: Add SMBus alert support")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
[wsa: fixed a typo in the commit message]
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 37c526f00bc1c4f847fc800085f8f009d2e11be6 ]
The following messages were observed while testing alert functionality
on systems with multiple I2C devices on a single bus if alert was active
on more than one chip.
smbus_alert 3-000c: SMBALERT# from dev 0x0c, flag 0
smbus_alert 3-000c: no driver alert()!
and:
smbus_alert 3-000c: SMBALERT# from dev 0x28, flag 0
Once it starts, this message repeats forever at high rate. There is no
device at any of the reported addresses.
Analysis shows that this is seen if multiple devices have the alert pin
active. Apparently some devices do not support SMBus arbitration correctly.
They keep sending address bits after detecting an address collision and
handle the collision not at all or too late.
Specifically, address 0x0c is seen with ADT7461A at address 0x4c and
ADM1021 at address 0x18 if alert is active on both chips. Address 0x28 is
seen with ADT7483 at address 0x2a and ADT7461 at address 0x4c if alert is
active on both chips.
Once the system is in bad state (alert is set by more than one chip),
it often only recovers by power cycling.
To reduce the impact of this problem, abort the endless loop in
smbus_alert() if the same address is read more than once and not
handled by a driver.
Fixes: b5527a7766f0 ("i2c: Add SMBus alert support")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
[wsa: it also fixed an interrupt storm in one of my experiments]
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
[wsa: rebased, moved a comment as well, improved the 'invalid' value]
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
