Re: [PATCH v3 2/3] usb: dwc3: add common driver to support flattened DT

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

On Sun, May 18, 2025, Ze Huang wrote:
> To support flattened dwc3 dt model and drop the glue layer, introduce the
> `dwc3-common` driver. This enables direct binding of the DWC3 core driver
> and offers an alternative to the existing glue driver `dwc3-of-simple`.
> 
> Signed-off-by: Ze Huang <huangze@whut.edu.cn>
> ---
>  drivers/usb/dwc3/Kconfig       |   9 ++
>  drivers/usb/dwc3/Makefile      |   1 +
>  drivers/usb/dwc3/dwc3-common.c | 191 +++++++++++++++++++++++++++++++++++++++++

Let's rename the dwc3-common to dwc3-generic-plat. I'd associate
"common" to common code that exists in all drivers; where as this is
mainly for generic platform driver.

>  3 files changed, 201 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/Kconfig b/drivers/usb/dwc3/Kconfig
> index 310d182e10b50b253d7e5a51674806e6ec442a2a..852f94f906e4f339dcbb562e1ce708409ba77b76 100644
> --- a/drivers/usb/dwc3/Kconfig
> +++ b/drivers/usb/dwc3/Kconfig
> @@ -118,6 +118,15 @@ config USB_DWC3_OF_SIMPLE
>  	  Currently supports Xilinx and Qualcomm DWC USB3 IP.
>  	  Say 'Y' or 'M' if you have one such device.
>  
> +config USB_DWC3_COMMON

Let's rename to USB_DWC3_GENERIC_PLAT. I would expect to also have
USB_DWC3_GENERIC_PCI at some point in the future.

Side note: flattened driver for PCI driver will allow the dwc3
host controllers to take advantage of MSIX interrupts going through the
dwc3 code path.

> +       tristate "DWC3 Platform common Driver"
> +       depends on OF && COMMON_CLK
> +       default USB_DWC3
> +       help
> +         Support USB3 functionality in simple SoC integrations.
> +         Currently supports SpacemiT DWC USB3 IP.
> +         Say 'Y' or 'M' if you have one such device.
> +
>  config USB_DWC3_ST
>  	tristate "STMicroelectronics Platforms"
>  	depends on (ARCH_STI || COMPILE_TEST) && OF
> diff --git a/drivers/usb/dwc3/Makefile b/drivers/usb/dwc3/Makefile
> index 830e6c9e5fe073c1f662ce34b6a4a2da34c407a2..ad1b0705c4d464f19e79ed0c3c63d942446e4742 100644
> --- a/drivers/usb/dwc3/Makefile
> +++ b/drivers/usb/dwc3/Makefile
> @@ -57,3 +57,4 @@ obj-$(CONFIG_USB_DWC3_IMX8MP)		+= dwc3-imx8mp.o
>  obj-$(CONFIG_USB_DWC3_XILINX)		+= dwc3-xilinx.o
>  obj-$(CONFIG_USB_DWC3_OCTEON)		+= dwc3-octeon.o
>  obj-$(CONFIG_USB_DWC3_RTK)		+= dwc3-rtk.o
> +obj-$(CONFIG_USB_DWC3_COMMON)		+= dwc3-common.o
> diff --git a/drivers/usb/dwc3/dwc3-common.c b/drivers/usb/dwc3/dwc3-common.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..afd9a7bec14b68dfd4f2353d714041882660a1a4
> --- /dev/null
> +++ b/drivers/usb/dwc3/dwc3-common.c
> @@ -0,0 +1,191 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * dwc3-common.c - DesignWare USB3 common driver
> + *
> + * Copyright (C) 2025 Ze Huang <huangze@whut.edu.cn>
> + *
> + * Inspired by dwc3-qcom.c and dwc3-of-simple.c
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/of_platform.h>
> +#include <linux/of_address.h>
> +#include <linux/platform_device.h>
> +#include <linux/reset.h>
> +#include "glue.h"
> +
> +struct dwc3_common {
> +	struct device		*dev;
> +	struct dwc3		dwc;
> +	struct clk_bulk_data	*clks;
> +	int			num_clocks;
> +	struct reset_control	*resets;
> +};
> +
> +static int dwc3_common_probe(struct platform_device *pdev)
> +{
> +	struct dwc3_probe_data probe_data = {};
> +	struct device *dev = &pdev->dev;
> +	struct dwc3_common *dwc3c;
> +	struct resource *res;
> +	int ret;
> +
> +	dwc3c = devm_kzalloc(dev, sizeof(*dwc3c), GFP_KERNEL);
> +	if (!dwc3c)
> +		return -ENOMEM;
> +
> +	dwc3c->dev = dev;
> +
> +	platform_set_drvdata(pdev, dwc3c);
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!res) {
> +		dev_err(&pdev->dev, "missing memory resource\n");
> +		return -ENODEV;
> +	}
> +
> +	dwc3c->resets = of_reset_control_array_get_optional_exclusive(dev->of_node);
> +	if (IS_ERR(dwc3c->resets))
> +		return dev_err_probe(dev, PTR_ERR(dwc3c->resets), "failed to get reset\n");
> +
> +	ret = reset_control_assert(dwc3c->resets);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "failed to assert reset\n");
> +
> +	usleep_range(10, 1000);
> +
> +	ret = reset_control_deassert(dwc3c->resets);
> +	if (ret) {
> +		dev_err(dev, "failed to deassert reset\n");
> +		goto reset_assert;
> +	}
> +
> +	ret = clk_bulk_get_all(dwc3c->dev, &dwc3c->clks);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to get clocks\n");
> +		goto reset_assert;
> +	}
> +
> +	dwc3c->num_clocks = ret;
> +
> +	ret = clk_bulk_prepare_enable(dwc3c->num_clocks, dwc3c->clks);
> +	if (ret) {
> +		dev_err(dev, "failed to enable clocks\n");
> +		goto reset_assert;
> +	}
> +
> +	dwc3c->dwc.dev = dev;
> +	probe_data.dwc = &dwc3c->dwc;
> +	probe_data.res = res;
> +	probe_data.ignore_clocks_and_resets = true;
> +	ret = dwc3_core_probe(&probe_data);
> +	if (ret)  {
> +		dev_err(dev, "failed to register DWC3 Core\n");
> +		goto clk_disable;
> +	}
> +
> +	return 0;
> +
> +clk_disable:
> +	clk_bulk_disable_unprepare(dwc3c->num_clocks, dwc3c->clks);
> +	clk_bulk_put_all(dwc3c->num_clocks, dwc3c->clks);
> +
> +reset_assert:
> +	reset_control_assert(dwc3c->resets);
> +
> +	return ret;
> +}
> +
> +static void dwc3_common_remove(struct platform_device *pdev)
> +{
> +	struct dwc3_common *dwc3c = platform_get_drvdata(pdev);
> +
> +	dwc3_core_remove(&dwc3c->dwc);
> +
> +	clk_bulk_disable_unprepare(dwc3c->num_clocks, dwc3c->clks);
> +	clk_bulk_put_all(dwc3c->num_clocks, dwc3c->clks);
> +
> +	reset_control_assert(dwc3c->resets);
> +}
> +
> +#ifdef CONFIG_PM_SLEEP

Use the new SYSTEM_SLEEP_PM_OPS macros and we can do away with these PM
guards.

> +static int dwc3_common_suspend(struct device *dev)
> +{
> +	struct dwc3_common *dwc3c = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = dwc3_pm_suspend(&dwc3c->dwc);
> +	if (ret)
> +		return ret;
> +
> +	clk_bulk_disable_unprepare(dwc3c->num_clocks, dwc3c->clks);
> +
> +	return 0;
> +}
> +
> +static int dwc3_common_resume(struct device *dev)
> +{
> +	struct dwc3_common *dwc3c = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = clk_bulk_prepare_enable(dwc3c->num_clocks, dwc3c->clks);
> +	if (ret)
> +		return ret;
> +
> +	ret = dwc3_pm_resume(&dwc3c->dwc);
> +	if (ret)
> +		return ret;
> +
> +	return 0;
> +}
> +
> +static int dwc3_common_runtime_suspend(struct device *dev)
> +{
> +	struct dwc3_common *dwc3c = dev_get_drvdata(dev);
> +
> +	return dwc3_runtime_suspend(&dwc3c->dwc);
> +}
> +
> +static int dwc3_common_runtime_resume(struct device *dev)
> +{
> +	struct dwc3_common *dwc3c = dev_get_drvdata(dev);
> +
> +	return dwc3_runtime_resume(&dwc3c->dwc);
> +}
> +
> +static int dwc3_common_runtime_idle(struct device *dev)
> +{
> +	struct dwc3_common *dwc3c = dev_get_drvdata(dev);
> +
> +	return dwc3_runtime_idle(&dwc3c->dwc);
> +}
> +
> +static const struct dev_pm_ops dwc3_common_dev_pm_ops = {
> +	SET_SYSTEM_SLEEP_PM_OPS(dwc3_common_suspend, dwc3_common_resume)
> +	RUNTIME_PM_OPS(dwc3_common_runtime_suspend, dwc3_common_runtime_resume,
> +		       dwc3_common_runtime_idle)
> +};
> +#endif /* CONFIG_PM_SLEEP */
> +
> +static const struct of_device_id dwc3_common_of_match[] = {
> +	{ .compatible = "spacemit,k1-dwc3", },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, dwc3_common_of_match);
> +
> +static struct platform_driver dwc3_common_driver = {
> +	.probe		= dwc3_common_probe,
> +	.remove		= dwc3_common_remove,
> +	.driver		= {
> +		.name	= "dwc3-common",
> +		.of_match_table = dwc3_common_of_match,
> +#ifdef CONFIG_PM_SLEEP
> +		.pm	= &dwc3_common_dev_pm_ops,
> +#endif /* CONFIG_PM_SLEEP */
> +	},
> +};
> +module_platform_driver(dwc3_common_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("DesignWare USB3 common driver");
> 
> -- 
> 2.49.0
> 

Thanks for the work. Going forward, I hope more platforms will move to
this and take advantage of this new flattened model.

Thanks,
Thinh