linux-kernel - Re: [PATCH v1] usb: dwc3: core: Add shutdown callback for dwc3

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Message-ID: <161655669850.3012082.11672497224863339022@swboyd.mtv.corp.google.com>
Date:   Tue, 23 Mar 2021 20:31:38 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Doug Anderson <dianders@...omium.org>,
        Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Sandeep Maheswaram <sanm@...eaurora.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, Manu Gautam <mgautam@...eaurora.org>,
        Sandeep Maheswaram <sanm@...eaurora.org>
Subject: Re: [PATCH v1] usb: dwc3: core: Add shutdown callback for dwc3

Quoting Sandeep Maheswaram (2021-03-23 12:27:32)
> This patch adds a shutdown callback to USB DWC core driver to ensure that
> it is properly shutdown in reboot/shutdown path. This is required
> where SMMU address translation is enabled like on SC7180
> SoC and few others. If the hardware is still accessing memory after
> SMMU translation is disabled as part of SMMU shutdown callback in
> system reboot or shutdown path, then IOVAs(I/O virtual address)
> which it was using will go on the bus as the physical addresses which
> might result in unknown crashes (NoC/interconnect errors).
> 
> Previously this was added in dwc3 qcom glue driver.
> https://patchwork.kernel.org/project/linux-arm-msm/list/?series=382449
> But observed kernel panic as glue driver shutdown getting called after
> iommu shutdown. As we are adding iommu nodes in dwc core node
> in device tree adding shutdown callback in core driver seems correct.
> 
> Signed-off-by: Sandeep Maheswaram <sanm@...eaurora.org>
> ---
>  drivers/usb/dwc3/core.c | 26 +++++++++++++++++++-------
>  1 file changed, 19 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 94fdbe5..777b2b5 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1634,11 +1634,9 @@ static int dwc3_probe(struct platform_device *pdev)
>         return ret;
>  }
>  
> -static int dwc3_remove(struct platform_device *pdev)
> +static void __dwc3_teardown(struct dwc3 *dwc)
>  {
> -       struct dwc3     *dwc = platform_get_drvdata(pdev);
> -
> -       pm_runtime_get_sync(&pdev->dev);
> +       pm_runtime_get_sync(dwc->dev);
>  
>         dwc3_debugfs_exit(dwc);
>         dwc3_core_exit_mode(dwc);
> @@ -1646,19 +1644,32 @@ static int dwc3_remove(struct platform_device *pdev)
>         dwc3_core_exit(dwc);
>         dwc3_ulpi_exit(dwc);
>  
> -       pm_runtime_disable(&pdev->dev);
> -       pm_runtime_put_noidle(&pdev->dev);
> -       pm_runtime_set_suspended(&pdev->dev);
> +       pm_runtime_disable(dwc->dev);
> +       pm_runtime_put_noidle(dwc->dev);
> +       pm_runtime_set_suspended(dwc->dev);
>  
>         dwc3_free_event_buffers(dwc);
>         dwc3_free_scratch_buffers(dwc);
>  
>         if (dwc->usb_psy)
>                 power_supply_put(dwc->usb_psy);
> +}
> +
> +static int dwc3_remove(struct platform_device *pdev)
> +{
> +       struct dwc3     *dwc = platform_get_drvdata(pdev);
> +
> +       __dwc3_teardown(dwc);
>  
>         return 0;
>  }
>  
> +static void dwc3_shutdown(struct platform_device *pdev)
> +{
> +       struct dwc3     *dwc = platform_get_drvdata(pdev);
> +
> +       __dwc3_teardown(dwc);
> +}

Can't this be

	static void dwc3_shutdown(struct platform_device *pdev)
	{
	       dwc3_remove(pdev);
	}

and then there's nothing else to change? Basically ignore return value
of dwc3_remove() to make shutdown and remove harmonize. I also wonder if
this is more common than we think and a struct driver flag could be set
to say "call remove for shutdown" and then have driver core swizzle on
that and save some duplicate functions.

>  #ifdef CONFIG_PM
>  static int dwc3_core_init_for_resume(struct dwc3 *dwc)
>  {
> @@ -1976,6 +1987,7 @@ MODULE_DEVICE_TABLE(acpi, dwc3_acpi_match);
>  static struct platform_driver dwc3_driver = {
>         .probe          = dwc3_probe,
>         .remove         = dwc3_remove,
> +       .shutdown   = dwc3_shutdown,