Re: [PATCH v2] bus: mhi: Fix race while handling SYS_ERR at power up

[Hemant Kumar <hemantk@codeaurora.org>]

Adding same comment in v2
On 11/8/2021 9:49 AM, Manivannan Sadhasivam wrote:
> Some devices tend to trigger SYS_ERR interrupt while the host handling
> SYS_ERR state of the device during power up. This creates a race
> condition and causes a failure in booting up the device.
> 
> The issue is seen on the Sierra Wireless EM9191 modem during SYS_ERR
> handling in mhi_async_power_up(). Once the host detects that the device
> is in SYS_ERR state, it issues MHI_RESET and waits for the device to
> process the reset request. During this time, the device triggers SYS_ERR
Device is not triggering the SYS_ERR interrupt, interrupt was triggered 
due to MHI RESET was getting cleared by device.
> interrupt to the host and host starts handling SYS_ERR execution.
"As interrupts are setup, MHI reset results in device clearing the reset 
and it sends incoming BHI interrupt with state still seen as SYS_ERROR 
instead of READY."

> 
> So by the time the device has completed reset, host starts SYS_ERR
> handling. This causes the race condition and the modem fails to boot.
> 
> Hence, register the IRQ handler only after handling the SYS_ERR check
> to avoid getting spurious IRQs from the device.
> 
> Cc: stable@vger.kernel.org
> Fixes: e18d4e9fa79b ("bus: mhi: core: Handle syserr during power_up")
> Reported-by: Aleksander Morgado <aleksander@aleksander.es>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> ---
[..]
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
Forum, a Linux Foundation Collaborative Project