linux-kernel - Re: [PATCH v2 1/5] bus: mhi: core: Handle syserr during power

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Date:   Wed, 22 Apr 2020 14:16:02 -0600
From:   Jeffrey Hugo <jhugo@...eaurora.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Bhaumik Vasav Bhatt <bbhatt@...eaurora.org>,
        Hemant Kumar <hemantk@...eaurora.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/5] bus: mhi: core: Handle syserr during power_up

On 4/21/2020 12:08 AM, Manivannan Sadhasivam wrote:
> On Mon, Apr 13, 2020 at 08:01:36AM -0600, Jeffrey Hugo wrote:
>> On 4/13/2020 7:34 AM, Manivannan Sadhasivam wrote:
>>> On Fri, Apr 10, 2020 at 03:39:57PM -0600, Jeffrey Hugo wrote:
>>>> On 4/10/2020 2:37 PM, Bhaumik Vasav Bhatt wrote:
>>>>> Hi Jeff,
>>>>>
>>>>> We will always have the mhi_intvec_handler registered and trigger your
>>>>> wake_up state event when you write MHI RESET. BHI INTVEC IRQ using
>>>>> mhi_cntrl->irq[0] is _not_ unregistered once you enter AMSS EE.
>>>>
>>>> I understand it is not unregistered.  However mhi_cntrl->irq[0] may be
>>>> reserved for BHI, and thus only exercised by PBL EE.  Where as,
>>>> mhi_cntrl->irq[1..N] may be only exercised by AMSS EE. mhi_intvec_handler is
>>>> not called in response to mhi_cntrl->irq[1..N].
>>>>
>>>> Additionally, I re-reviewed the MHI spec, and I don't see where the spec
>>>> requires the device to issue an interrupt upon completion of the RESET
>>>> request.
>>>>
>>>> Under section 3.5, step 11 states -
>>>>
>>>> "The host must poll for the value of the RESET bit to detect the completion
>>>> of the reset procedure by the device (RESET is set to 0)."
>>>>
>>>
>>> If this is the scenario then we need to change all of the wait_event_timeout()
>>> implementation for MHI RESET in current stack to polling.
>>>
>>> Or the interrupt generation is not defined in spec (sheet) but part of the
>>> existing implementation?
>>
>> It probably could be considered part of the existing implementation, but I'd
>> like to hear from Hemant/Bhaumik.  Wherever we end up, I'd like to have the
>> spec match.
> 
> Hemant/Bhaumik, can you please share your thoughts?

Sorry.  Hemant, Bhaumik, and I have had a few calls discussing this.  We 
are trying to come to a consensus on the expectation of the device 
behavior, so that we can propose the best solution.  Probably a few more 
days yet while we await for a bit of clarification.

-- 
Jeffrey Hugo
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.