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

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Date:   Tue, 21 Apr 2020 11:38:35 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Jeffrey Hugo <jhugo@...eaurora.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 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?

Thanks,
Mani

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