Re: [PATCH 04/12] usb: dwc3: Expose core driver as library

[Thinh Nguyen]

On Mon, Oct 16, 2023, Bjorn Andersson wrote:
> The DWC3 IP block is handled by three distinct device drivers: XHCI,
> DWC3 core and a platform specific (optional) DWC3 glue driver.
> 
> This has resulted in, at least in the case of the Qualcomm glue, the
> presence of a number of layering violations, where the glue code either
> can't handle, or has to work around, the fact that core might not probe
> deterministically.
> 
> An example of this is that the suspend path should operate slightly
> different depending on the device operating in host or peripheral mode,
> and the only way to determine the operating state is to peek into the
> core's drvdata.
> 
> The Qualcomm glue driver is expected to make updates in the qscratch
> register region (the "glue" region) during role switch events, but with
> the glue and core split using the driver model, there is no reasonable
> way to introduce listeners for mode changes.
> 
> Split the dwc3 core platfrom_driver callbacks and their implementation
> and export the implementation, to make it possible to deterministically
> instantiate the dwc3 core as part of the dwc3 glue drivers and to
> allow flattening of the DeviceTree representation.
> 
> Signed-off-by: Bjorn Andersson <quic_bjorande@xxxxxxxxxxx>
> ---
>  drivers/usb/dwc3/core.c | 134 ++++++++++++++++++++++++++++++++----------------
>  drivers/usb/dwc3/core.h |  10 ++++
>  2 files changed, 100 insertions(+), 44 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index d25490965b27..71e376bebb16 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1876,7 +1876,7 @@ static int dwc3_get_clocks(struct dwc3 *dwc)
>  	return 0;
>  }
>  
> -static int dwc3_probe(struct platform_device *pdev)
> +struct dwc3 *dwc3_probe(struct platform_device *pdev)
>  {
>  	struct device		*dev = &pdev->dev;
>  	struct resource		*res, dwc_res;
> @@ -1886,14 +1886,14 @@ static int dwc3_probe(struct platform_device *pdev)
>  
>  	dwc = devm_kzalloc(dev, sizeof(*dwc), GFP_KERNEL);
>  	if (!dwc)
> -		return -ENOMEM;
> +		return ERR_PTR(-ENOMEM);
>  
>  	dwc->dev = dev;
>  
>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>  	if (!res) {
>  		dev_err(dev, "missing memory resource\n");
> -		return -ENODEV;
> +		return ERR_PTR(-ENODEV);
>  	}
>  
>  	dwc->xhci_resources[0].start = res->start;
> @@ -1922,7 +1922,7 @@ static int dwc3_probe(struct platform_device *pdev)
>  
>  	regs = devm_ioremap_resource(dev, &dwc_res);
>  	if (IS_ERR(regs))
> -		return PTR_ERR(regs);
> +		return ERR_CAST(regs);
>  
>  	dwc->regs	= regs;
>  	dwc->regs_size	= resource_size(&dwc_res);
> @@ -1953,7 +1953,6 @@ static int dwc3_probe(struct platform_device *pdev)
>  		goto err_disable_clks;
>  	}
>  
> -	platform_set_drvdata(pdev, dwc);
>  	dwc3_cache_hwparams(dwc);
>  
>  	if (!dwc->sysdev_is_parent &&
> @@ -2006,7 +2005,7 @@ static int dwc3_probe(struct platform_device *pdev)
>  
>  	pm_runtime_put(dev);
>  
> -	return 0;
> +	return dwc;
>  
>  err_exit_debugfs:
>  	dwc3_debugfs_exit(dwc);
> @@ -2030,14 +2029,26 @@ static int dwc3_probe(struct platform_device *pdev)
>  	if (dwc->usb_psy)
>  		power_supply_put(dwc->usb_psy);
>  
> -	return ret;
> +	return ERR_PTR(ret);
>  }
> +EXPORT_SYMBOL_GPL(dwc3_probe);
>  
> -static void dwc3_remove(struct platform_device *pdev)
> +static int dwc3_plat_probe(struct platform_device *pdev)
>  {
> -	struct dwc3	*dwc = platform_get_drvdata(pdev);
> +	struct dwc3 *dwc;
> +
> +	dwc = dwc3_probe(pdev);
> +	if (IS_ERR(dwc))
> +		return PTR_ERR(dwc);
> +
> +	platform_set_drvdata(pdev, dwc);
> +
> +	return 0;
> +}
>  
> -	pm_runtime_get_sync(&pdev->dev);
> +void dwc3_remove(struct dwc3 *dwc)
> +{
> +	pm_runtime_get_sync(dwc->dev);
>  
>  	dwc3_core_exit_mode(dwc);
>  	dwc3_debugfs_exit(dwc);
> @@ -2045,22 +2056,28 @@ static void dwc3_remove(struct platform_device *pdev)
>  	dwc3_core_exit(dwc);
>  	dwc3_ulpi_exit(dwc);
>  
> -	pm_runtime_allow(&pdev->dev);
> -	pm_runtime_disable(&pdev->dev);
> -	pm_runtime_dont_use_autosuspend(&pdev->dev);
> -	pm_runtime_put_noidle(&pdev->dev);
> +	pm_runtime_allow(dwc->dev);
> +	pm_runtime_disable(dwc->dev);
> +	pm_runtime_dont_use_autosuspend(dwc->dev);
> +	pm_runtime_put_noidle(dwc->dev);
>  	/*
>  	 * HACK: Clear the driver data, which is currently accessed by parent
>  	 * glue drivers, before allowing the parent to suspend.
>  	 */
> -	platform_set_drvdata(pdev, NULL);
> -	pm_runtime_set_suspended(&pdev->dev);
> +	dev_set_drvdata(dwc->dev, NULL);
> +	pm_runtime_set_suspended(dwc->dev);
>  
>  	dwc3_free_event_buffers(dwc);
>  
>  	if (dwc->usb_psy)
>  		power_supply_put(dwc->usb_psy);
>  }
> +EXPORT_SYMBOL_GPL(dwc3_remove);
> +
> +static void dwc3_plat_remove(struct platform_device *pdev)
> +{
> +	dwc3_remove(platform_get_drvdata(pdev));
> +}
>  
>  #ifdef CONFIG_PM
>  static int dwc3_core_init_for_resume(struct dwc3 *dwc)
> @@ -2227,9 +2244,8 @@ static int dwc3_runtime_checks(struct dwc3 *dwc)
>  	return 0;
>  }
>  
> -static int dwc3_runtime_suspend(struct device *dev)
> +int dwc3_runtime_suspend(struct dwc3 *dwc)
>  {
> -	struct dwc3     *dwc = dev_get_drvdata(dev);
>  	int		ret;
>  
>  	if (dwc3_runtime_checks(dwc))
> @@ -2241,10 +2257,10 @@ static int dwc3_runtime_suspend(struct device *dev)
>  
>  	return 0;
>  }
> +EXPORT_SYMBOL_GPL(dwc3_runtime_suspend);
>  
> -static int dwc3_runtime_resume(struct device *dev)
> +int dwc3_runtime_resume(struct dwc3 *dwc)
>  {
> -	struct dwc3     *dwc = dev_get_drvdata(dev);
>  	int		ret;
>  
>  	ret = dwc3_resume_common(dwc, PMSG_AUTO_RESUME);
> @@ -2261,15 +2277,14 @@ static int dwc3_runtime_resume(struct device *dev)
>  		break;
>  	}
>  
> -	pm_runtime_mark_last_busy(dev);
> +	pm_runtime_mark_last_busy(dwc->dev);
>  
>  	return 0;
>  }
> +EXPORT_SYMBOL_GPL(dwc3_runtime_resume);
>  
> -static int dwc3_runtime_idle(struct device *dev)
> +int dwc3_runtime_idle(struct dwc3 *dwc)
>  {
> -	struct dwc3     *dwc = dev_get_drvdata(dev);
> -
>  	switch (dwc->current_dr_role) {
>  	case DWC3_GCTL_PRTCAP_DEVICE:
>  		if (dwc3_runtime_checks(dwc))
> @@ -2281,49 +2296,64 @@ static int dwc3_runtime_idle(struct device *dev)
>  		break;
>  	}
>  
> -	pm_runtime_mark_last_busy(dev);
> -	pm_runtime_autosuspend(dev);
> +	pm_runtime_mark_last_busy(dwc->dev);
> +	pm_runtime_autosuspend(dwc->dev);
>  
>  	return 0;
>  }
> +EXPORT_SYMBOL_GPL(dwc3_runtime_idle);
> +
> +static int dwc3_plat_runtime_suspend(struct device *dev)
> +{
> +	return dwc3_runtime_suspend(dev_get_drvdata(dev));
> +}
> +
> +static int dwc3_plat_runtime_resume(struct device *dev)
> +{
> +	return dwc3_runtime_resume(dev_get_drvdata(dev));
> +}
> +
> +static int dwc3_plat_runtime_idle(struct device *dev)
> +{
> +	return dwc3_runtime_idle(dev_get_drvdata(dev));
> +}
>  #endif /* CONFIG_PM */
>  
>  #ifdef CONFIG_PM_SLEEP
> -static int dwc3_suspend(struct device *dev)
> +int dwc3_suspend(struct dwc3 *dwc)
>  {
> -	struct dwc3	*dwc = dev_get_drvdata(dev);
>  	int		ret;
>  
>  	ret = dwc3_suspend_common(dwc, PMSG_SUSPEND);
>  	if (ret)
>  		return ret;
>  
> -	pinctrl_pm_select_sleep_state(dev);
> +	pinctrl_pm_select_sleep_state(dwc->dev);
>  
>  	return 0;
>  }
> +EXPORT_SYMBOL_GPL(dwc3_suspend);
>  
> -static int dwc3_resume(struct device *dev)
> +int dwc3_resume(struct dwc3 *dwc)
>  {
> -	struct dwc3	*dwc = dev_get_drvdata(dev);
>  	int		ret;
>  
> -	pinctrl_pm_select_default_state(dev);
> +	pinctrl_pm_select_default_state(dwc->dev);
>  
>  	ret = dwc3_resume_common(dwc, PMSG_RESUME);
>  	if (ret)
>  		return ret;
>  
> -	pm_runtime_disable(dev);
> -	pm_runtime_set_active(dev);
> -	pm_runtime_enable(dev);
> +	pm_runtime_disable(dwc->dev);
> +	pm_runtime_set_active(dwc->dev);
> +	pm_runtime_enable(dwc->dev);
>  
>  	return 0;
>  }
> +EXPORT_SYMBOL_GPL(dwc3_resume);
>  
> -static void dwc3_complete(struct device *dev)
> +void dwc3_complete(struct dwc3 *dwc)
>  {
> -	struct dwc3	*dwc = dev_get_drvdata(dev);
>  	u32		reg;
>  
>  	if (dwc->current_dr_role == DWC3_GCTL_PRTCAP_HOST &&
> @@ -2333,15 +2363,31 @@ static void dwc3_complete(struct device *dev)
>  		dwc3_writel(dwc->regs, DWC3_GUCTL3, reg);
>  	}
>  }
> +EXPORT_SYMBOL_GPL(dwc3_complete);
> +
> +static int dwc3_plat_suspend(struct device *dev)
> +{
> +	return dwc3_suspend(dev_get_drvdata(dev));
> +}
> +
> +static int dwc3_plat_resume(struct device *dev)
> +{
> +	return dwc3_resume(dev_get_drvdata(dev));
> +}
> +
> +static void dwc3_plat_complete(struct device *dev)
> +{
> +	dwc3_complete(dev_get_drvdata(dev));
> +}
>  #else
> -#define dwc3_complete NULL
> +#define dwc3_plat_complete NULL
>  #endif /* CONFIG_PM_SLEEP */
>  
>  static const struct dev_pm_ops dwc3_dev_pm_ops = {
> -	SET_SYSTEM_SLEEP_PM_OPS(dwc3_suspend, dwc3_resume)
> -	.complete = dwc3_complete,
> -	SET_RUNTIME_PM_OPS(dwc3_runtime_suspend, dwc3_runtime_resume,
> -			dwc3_runtime_idle)
> +	SET_SYSTEM_SLEEP_PM_OPS(dwc3_plat_suspend, dwc3_plat_resume)
> +	.complete = dwc3_plat_complete,
> +	SET_RUNTIME_PM_OPS(dwc3_plat_runtime_suspend, dwc3_plat_runtime_resume,
> +			   dwc3_plat_runtime_idle)
>  };
>  
>  #ifdef CONFIG_OF
> @@ -2369,8 +2415,8 @@ MODULE_DEVICE_TABLE(acpi, dwc3_acpi_match);
>  #endif
>  
>  static struct platform_driver dwc3_driver = {
> -	.probe		= dwc3_probe,
> -	.remove_new	= dwc3_remove,
> +	.probe		= dwc3_plat_probe,
> +	.remove_new	= dwc3_plat_remove,
>  	.driver		= {
>  		.name	= "dwc3",
>  		.of_match_table	= of_match_ptr(of_dwc3_match),
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index c6c87acbd376..f5e22559bb73 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -1568,6 +1568,16 @@ void dwc3_event_buffers_cleanup(struct dwc3 *dwc);
>  
>  int dwc3_core_soft_reset(struct dwc3 *dwc);
>  
> +struct dwc3 *dwc3_probe(struct platform_device *pdev);
> +void dwc3_remove(struct dwc3 *dwc);
> +
> +int dwc3_runtime_suspend(struct dwc3 *dwc);
> +int dwc3_runtime_resume(struct dwc3 *dwc);
> +int dwc3_runtime_idle(struct dwc3 *dwc);
> +int dwc3_suspend(struct dwc3 *dwc);
> +int dwc3_resume(struct dwc3 *dwc);
> +void dwc3_complete(struct dwc3 *dwc);
> +

Can we make this new interface clear? It's being buried under core.h
this way. Perhaps add some comments and divider, or move to another
header file?

Thanks,
Thinh

>  #if IS_ENABLED(CONFIG_USB_DWC3_HOST) || IS_ENABLED(CONFIG_USB_DWC3_DUAL_ROLE)
>  int dwc3_host_init(struct dwc3 *dwc);
>  void dwc3_host_exit(struct dwc3 *dwc);
> 
> -- 
> 2.25.1
>