linux-kernel - Re: [PATCH v2] bus: mhi: host: pci_generic: Add missing poweroff() PM callback

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Message-ID: <daafdfd8-312e-cf42-d7bb-3fb914d443dc@quicinc.com>
Date:   Tue, 5 Apr 2022 13:23:22 -0700
From:   Bhaumik Vasav Bhatt <quic_bbhatt@...cinc.com>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        <mhi@...ts.linux.dev>
CC:     <quic_hemantk@...cinc.com>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <loic.poulain@...aro.org>,
        <stable@...r.kernel.org>
Subject: Re: [PATCH v2] bus: mhi: host: pci_generic: Add missing poweroff() PM
 callback


On 4/5/2022 5:59 AM, Manivannan Sadhasivam wrote:
> During hibernation process, once thaw() stage completes, the MHI endpoint
> devices will be in M0 state post recovery. After that, the devices will be
> powered down so that the system can enter the target sleep state. During
> this stage, the PCI core will put the devices in D3hot. But this transition
> is allowed by the MHI spec. The devices can only enter D3hot when it is in
> M3 state.
>
> So for fixing this issue, let's add the poweroff() callback that will get
> executed before putting the system in target sleep state during
> hibernation. This callback will power down the device properly so that it
> could be restored during restore() or thaw() stage.
>
> Cc: stable@...r.kernel.org
> Fixes: 5f0c2ee1fe8d ("bus: mhi: pci-generic: Fix hibernation")
> Reported-by: Hemant Kumar <quic_hemantk@...cinc.com>
> Suggested-by: Hemant Kumar <quic_hemantk@...cinc.com>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
>
> Changes in v2:
>
> * Hemant suggested to use restore function for poweroff() callback as we can
> make sure that the device gets powered down properly.
>
>   drivers/bus/mhi/host/pci_generic.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/drivers/bus/mhi/host/pci_generic.c b/drivers/bus/mhi/host/pci_generic.c
> index 9527b7d63840..ef85dbfb3216 100644
> --- a/drivers/bus/mhi/host/pci_generic.c
> +++ b/drivers/bus/mhi/host/pci_generic.c
> @@ -1085,6 +1085,7 @@ static const struct dev_pm_ops mhi_pci_pm_ops = {
>   	.resume = mhi_pci_resume,
>   	.freeze = mhi_pci_freeze,
>   	.thaw = mhi_pci_restore,
> +	.poweroff = mhi_pci_freeze,

It is possible that .thaw() queues recovery work and recovery work is 
still running

while .poweroff() is called. I would suggest adding a flush_work() in 
freeze such that

we don't try to power off while we're also trying to power on MHI from 
recovery work.

>   	.restore = mhi_pci_restore,
>   #endif
>   };