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

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Date:   Mon, 13 Apr 2020 08:01:36 -0600
From:   Jeffrey Hugo <jhugo@...eaurora.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     Bhaumik Vasav Bhatt <bbhatt@...eaurora.org>,
        Hemant Kumar <hemantk@...eaurora.org>,
        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 4/13/2020 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.

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