From: Jeffrey Hugo <quic_jhugo@quicinc.com>
To: Hemant Kumar <hemantk@codeaurora.org>,
Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
<mhi@lists.linux.dev>
Cc: <aleksander@aleksander.es>, <loic.poulain@linaro.org>,
<thomas.perrot@bootlin.com>, <bbhatt@codeaurora.org>,
<linux-arm-msm@vger.kernel.org>, <stable@vger.kernel.org>
Subject: Re: [PATCH v2] bus: mhi: Fix race while handling SYS_ERR at power up
Date: Wed, 17 Nov 2021 10:24:24 -0700 [thread overview]
Message-ID: <c6fd34ff-7f19-2ab1-ee3c-f6be178bf9a2@quicinc.com> (raw)
In-Reply-To: <51338f3b-4c85-17b6-971b-44a50d59a262@codeaurora.org>
On 11/8/2021 12:06 PM, Hemant Kumar wrote:
> 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.
Shouldn't the device state be RESET and not SYS_ERR at that point?
The device will enter SYS_ERR (and trigger an interrupt for that). Host
issues MHI_RESET. Device is expected to clear SYS_ERR and enter the
RESET state. Then the device clears MHI_RESET. Device can then trigger
an interrupt to signal the state change (per the updated spec).
I was going to add my reviewed-by, but I'm confused by your comment.
>> 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>
>> ---
> [..]
next prev parent reply other threads:[~2021-11-17 17:24 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-08 17:49 [PATCH v2] bus: mhi: Fix race while handling SYS_ERR at power up Manivannan Sadhasivam
2021-11-08 19:01 ` Bhaumik Bhatt
2021-11-08 19:06 ` Hemant Kumar
2021-11-17 17:24 ` Jeffrey Hugo [this message]
2021-11-17 20:20 ` Hemant Kumar
2021-11-18 5:36 ` Manivannan Sadhasivam
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