linux-kernel - Re: [PATCH V2 1/1] soc: qcom: smp2p: Add wakeup capability to SMP2P IRQ

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Date:   Mon, 16 Aug 2021 13:23:18 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Deepak Kumar Singh <deesin@...eaurora.org>,
        bjorn.andersson@...aro.org, clew@...eaurora.org,
        sibis@...eaurora.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, Andy Gross <agross@...nel.org>
Subject: Re: [PATCH V2 1/1] soc: qcom: smp2p: Add wakeup capability to SMP2P IRQ

Quoting Deepak Kumar Singh (2021-08-16 03:05:35)
> Remote susbsystems notify fatal crash throught smp2p interrupt.
> When modem/wifi crashes it can cause soc to come out of low power state
> and may not allow again to enter in low power state until crash is handled.
>
> Mark smp2p interrupt wakeup capable so that interrupt handler is executed
> and remote susbsystem crash can be handled in system  resume path.
>
> Signed-off-by: Deepak Kumar Singh <deesin@...eaurora.org>
> ---
>  drivers/soc/qcom/smp2p.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/drivers/soc/qcom/smp2p.c b/drivers/soc/qcom/smp2p.c
> index 2df4883..646848b 100644
> --- a/drivers/soc/qcom/smp2p.c
> +++ b/drivers/soc/qcom/smp2p.c
> @@ -18,6 +18,7 @@
>  #include <linux/soc/qcom/smem.h>
>  #include <linux/soc/qcom/smem_state.h>
>  #include <linux/spinlock.h>
> +#include <linux/pm_wakeirq.h>

Please sort alphabetically by include name, 'p' before 's'.

>
>  /*
>   * The Shared Memory Point to Point (SMP2P) protocol facilitates communication
> @@ -538,9 +539,20 @@ static int qcom_smp2p_probe(struct platform_device *pdev)
>                 goto unwind_interfaces;
>         }
>
> +       /* Setup smp2p interrupt as wakeup source */

This comment is bad. Please don't reiterate what the code is doing.
Instead, write something like

	/*
	 * Treat remoteproc crashes as wakeups by default so we handle
	 * them sooner rather than along with the next wakeup (e.g.
	 * power button). This avoids leaving the system in a shallower
	 * suspend power state if a remoteproc crashes during suspend,
	 * but requires userspace to actively suspend the device after
	 * handling the crash, or CONFIG_PM_AUTOSLEEP to be true.
	 */

> +       ret = device_init_wakeup(&pdev->dev, true);

I still wonder if it's better to leave this off by default and only
enable it if the kernel is using autosuspend (PM_AUTOSLEEP). Then
userspace is responsible to decide if it can handle the wakeup with the
screen off, reload the remoteproc, and go back to suspend if it isn't
using autosuspend.

> +       if (ret)
> +               goto unwind_interfaces;
> +