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

[Sandeep Maheswaram <sanm@codeaurora.org>]

On 3/24/2021 9:01 AM, Stephen Boyd wrote:
> 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.

I was referring to similar patch 
https://patchwork.kernel.org/project/linux-usb/patch/20190817174140.6394-1-vicencb@gmail.com/

>>   #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,