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

Stephen Boyd
2021-03-24T03:32:24Z

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@codeaurora.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,