Re: [PATCH 4/5] usb: dwc3: glue: Allow more fine grained control over mode switches

[Sven Peter <sven@kernel.org>]

On 15.10.25 01:16, Thinh Nguyen wrote:
> On Mon, Oct 13, 2025, Sven Peter wrote:
>> We need fine grained control over mode switched on the DWC3 controller
>> present on Apple Silicon. Export core, host and gadget init and exit,
>> ptrcap and susphy control functions. Also introduce an additional
>> parameter to probe_data that allows to skip the final initialization
>> step that would bring up host or gadget mode.
>>
>> Signed-off-by: Sven Peter <sven@kernel.org>
>> ---
>>   drivers/usb/dwc3/core.c   |  16 +++++--
>>   drivers/usb/dwc3/gadget.c |   2 +
>>   drivers/usb/dwc3/glue.h   | 116 ++++++++++++++++++++++++++++++++++++++++++++++
>>   drivers/usb/dwc3/host.c   |   2 +
>>   4 files changed, 131 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>> index ae140c356295c03df3982ff4fa95f8638296e52d..526c0453b99aad79d99a842797e52d9290456d76 100644
>> --- a/drivers/usb/dwc3/core.c
>> +++ b/drivers/usb/dwc3/core.c
>> @@ -132,6 +132,7 @@ void dwc3_enable_susphy(struct dwc3 *dwc, bool enable)
>>   		dwc3_writel(dwc->regs, DWC3_GUSB2PHYCFG(i), reg);
>>   	}
>>   }
>> +EXPORT_SYMBOL_GPL(dwc3_enable_susphy);
>>   
>>   void dwc3_set_prtcap(struct dwc3 *dwc, u32 mode, bool ignore_susphy)
>>   {
>> @@ -158,6 +159,7 @@ void dwc3_set_prtcap(struct dwc3 *dwc, u32 mode, bool ignore_susphy)
>>   	dwc->current_dr_role = mode;
>>   	trace_dwc3_set_prtcap(mode);
>>   }
>> +EXPORT_SYMBOL_GPL(dwc3_set_prtcap);
>>   
>>   static void __dwc3_set_mode(struct work_struct *work)
>>   {
>> @@ -975,7 +977,7 @@ static void dwc3_clk_disable(struct dwc3 *dwc)
>>   	clk_disable_unprepare(dwc->bus_clk);
>>   }
>>   
>> -static void dwc3_core_exit(struct dwc3 *dwc)
>> +void dwc3_core_exit(struct dwc3 *dwc)
>>   {
>>   	dwc3_event_buffers_cleanup(dwc);
>>   	dwc3_phy_power_off(dwc);
>> @@ -983,6 +985,7 @@ static void dwc3_core_exit(struct dwc3 *dwc)
>>   	dwc3_clk_disable(dwc);
>>   	reset_control_assert(dwc->reset);
>>   }
>> +EXPORT_SYMBOL_GPL(dwc3_core_exit);
>>   
>>   static bool dwc3_core_is_valid(struct dwc3 *dwc)
>>   {
>> @@ -1328,7 +1331,7 @@ static void dwc3_config_threshold(struct dwc3 *dwc)
>>    *
>>    * Returns 0 on success otherwise negative errno.
>>    */
>> -static int dwc3_core_init(struct dwc3 *dwc)
>> +int dwc3_core_init(struct dwc3 *dwc)
>>   {
>>   	unsigned int		hw_mode;
>>   	u32			reg;
>> @@ -1528,6 +1531,7 @@ static int dwc3_core_init(struct dwc3 *dwc)
>>   
>>   	return ret;
>>   }
>> +EXPORT_SYMBOL_GPL(dwc3_core_init);
>>   
>>   static int dwc3_core_get_phy(struct dwc3 *dwc)
>>   {
>> @@ -2299,9 +2303,11 @@ int dwc3_core_probe(const struct dwc3_probe_data *data)
>>   	dwc3_check_params(dwc);
>>   	dwc3_debugfs_init(dwc);
>>   
>> -	ret = dwc3_core_init_mode(dwc);
>> -	if (ret)
>> -		goto err_exit_debugfs;
>> +	if (!data->skip_core_init_mode) {
>> +		ret = dwc3_core_init_mode(dwc);
>> +		if (ret)
>> +			goto err_exit_debugfs;
>> +	}
>>   
>>   	pm_runtime_put(dev);
>>   
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index 6f18b4840a25d176abb4134581ad0ce68ba19ffc..1f67fb6aead5725c2e7b553c635eab985c9e1d48 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -4810,6 +4810,7 @@ int dwc3_gadget_init(struct dwc3 *dwc)
>>   err0:
>>   	return ret;
>>   }
>> +EXPORT_SYMBOL_GPL(dwc3_gadget_init);
>>   
>>   /* -------------------------------------------------------------------------- */
>>   
>> @@ -4828,6 +4829,7 @@ void dwc3_gadget_exit(struct dwc3 *dwc)
>>   	dma_free_coherent(dwc->sysdev, sizeof(*dwc->ep0_trb) * 2,
>>   			  dwc->ep0_trb, dwc->ep0_trb_addr);
>>   }
>> +EXPORT_SYMBOL_GPL(dwc3_gadget_exit);
>>   
>>   int dwc3_gadget_suspend(struct dwc3 *dwc)
>>   {
>> diff --git a/drivers/usb/dwc3/glue.h b/drivers/usb/dwc3/glue.h
>> index 7f326cff12458901904d4c32f62ed9357d0f6e3b..376e7aa74281c13bfb3a85dc033622bcff8d2acb 100644
>> --- a/drivers/usb/dwc3/glue.h
>> +++ b/drivers/usb/dwc3/glue.h
>> @@ -15,11 +15,14 @@
>>    * @res: resource for the DWC3 core mmio region
>>    * @ignore_clocks_and_resets: clocks and resets defined for the device should
>>    *		be ignored by the DWC3 core, as they are managed by the glue
>> + * @skip_core_init_mode: Skip the finial initialization of the target mode, as
>> + *		it must be managed by the glue
>>    */
>>   struct dwc3_probe_data {
>>   	struct dwc3 *dwc;
>>   	struct resource *res;
>>   	bool ignore_clocks_and_resets;
>> +	bool skip_core_init_mode;
>>   };
>>   
>>   /**
>> @@ -60,4 +63,117 @@ int dwc3_pm_resume(struct dwc3 *dwc);
>>   void dwc3_pm_complete(struct dwc3 *dwc);
>>   int dwc3_pm_prepare(struct dwc3 *dwc);
>>   
>> +
>> +/* All of the following functions must only be used with skip_core_init_mode */
>> +
>> +/**
>> + * dwc3_core_init - Initialize DWC3 core hardware
>> + * @dwc: Pointer to DWC3 controller context
>> + *
>> + * Configures and initializes the core hardware, usually done by dwc3_core_probe.
>> + * This function is provided for platforms that use skip_core_init_mode and need
>> + * to finalize the core initialization after some platform-specific setup.
>> + * It must only be called when using skip_core_init_mode and before
>> + * dwc3_host_init or dwc3_gadget_init.
>> + *
>> + * Return: 0 on success, negative error code on failure
>> + */
>> +int dwc3_core_init(struct dwc3 *dwc);
>> +
>> +/**
>> + * dwc3_core_exit - Shut down DWC3 core hardware
>> + * @dwc: Pointer to DWC3 controller context
>> + *
>> + * Disables and cleans up the core hardware state. This is usually handled
>> + * internally by dwc3 and must only be called when using skip_core_init_mode
>> + * and only after dwc3_core_init. Afterwards, dwc3_core_init may be called
>> + * again.
>> + */
>> +void dwc3_core_exit(struct dwc3 *dwc);
>> +
>> +/**
>> + * dwc3_host_init - Initialize host mode operation
>> + * @dwc: Pointer to DWC3 controller context
>> + *
>> + * Initializes the controller for USB host mode operation, usually done by
>> + * dwc3_core_probe or from within the dwc3 USB role switch callback.
>> + * This function is provided for platforms that use skip_core_init_mode and need
>> + * to finalize the host initialization after some platform-specific setup.
>> + * It must not be called before dwc3_core_init or when skip_core_init_mode is
>> + * not used. It must also not be called when gadget or host mode has already
>> + * been initialized.
>> + *
>> + * Return: 0 on success, negative error code on failure
>> + */
>> +int dwc3_host_init(struct dwc3 *dwc);
>> +
>> +/**
>> + * dwc3_host_exit - Shut down host mode operation
>> + * @dwc: Pointer to DWC3 controller context
>> + *
>> + * Disables and cleans up host mode resources, usually done by
>> + * the dwc3 USB role switch callback before switching controller mode.
>> + * It must only be called when skip_core_init_mode is used and only after
>> + * dwc3_host_init.
>> + */
>> +void dwc3_host_exit(struct dwc3 *dwc);
>> +
>> +/**
>> + * dwc3_gadget_init - Initialize gadget mode operation
>> + * @dwc: Pointer to DWC3 controller context
>> + *
>> + * Initializes the controller for USB gadget mode operation, usually done by
>> + * dwc3_core_probe or from within the dwc3 USB role switch callback. This
>> + * function is provided for platforms that use skip_core_init_mode and need to
>> + * finalize the gadget initialization after some platform-specific setup.
>> + * It must not be called before dwc3_core_init or when skip_core_init_mode is
>> + * not used. It must also not be called when gadget or host mode has already
>> + * been initialized.
>> + *
>> + * Return: 0 on success, negative error code on failure
>> + */
>> +int dwc3_gadget_init(struct dwc3 *dwc);
>> +
>> +/**
>> + * dwc3_gadget_exit - Shut down gadget mode operation
>> + * @dwc: Pointer to DWC3 controller context
>> + *
>> + * Disables and cleans up gadget mode resources, usually done by
>> + * the dwc3 USB role switch callback before switching controller mode.
>> + * It must only be called when skip_core_init_mode is used and only after
>> + * dwc3_gadget_init.
>> + */
>> +void dwc3_gadget_exit(struct dwc3 *dwc);
>> +
>> +/**
>> + * dwc3_enable_susphy - Control SUSPHY status for all USB ports
>> + * @dwc: Pointer to DWC3 controller context
>> + * @enable: True to enable SUSPHY, false to disable
>> + *
>> + * Enables or disables the USB3 PHY SUSPEND and USB2 PHY SUSPHY feature for
>> + * all available ports.
>> + * This is usually handled by the dwc3 core code and should only be used
>> + * when skip_core_init_mode is used and the glue layer needs to manage SUSPHY
>> + * settings itself, e.g., due to platform-specific requirements during mode
>> + * switches.
>> + */
>> +void dwc3_enable_susphy(struct dwc3 *dwc, bool enable);
>> +
>> +/**
>> + * dwc3_set_prtcap - Set the USB controller PRTCAP mode
>> + * @dwc: Pointer to DWC3 controller context
>> + * @mode: Target mode, must be one of DWC3_GCTL_PRTCAP_{HOST,DEVICE,OTG}
>> + * @ignore_susphy: If true, skip disabling the SUSPHY and keep the current state
>> + *
>> + * Updates PRTCAP of the controller and current_dr_role inside the dwc3
>> + * structure. For DRD controllers, this also disables SUSPHY unless explicitly
>> + * told to skip via the ignore_susphy parameter.
>> + *
>> + * This is usually handled by the dwc3 core code and should only be used
>> + * when skip_core_init_mode is used and the glue layer needs to manage mode
>> + * transitions itself due to platform-specific requirements. It must be called
>> + * with the correct mode before calling dwc3_host_init or dwc3_gadget_init.
>> + */
>> +void dwc3_set_prtcap(struct dwc3 *dwc, u32 mode, bool ignore_susphy);
>> +
>>   #endif
>> diff --git a/drivers/usb/dwc3/host.c b/drivers/usb/dwc3/host.c
>> index e77fd86d09cf0a36161c20ad3c83f10e67099775..cf6512ed17a69134e6ca1b884f76c1439693fab1 100644
>> --- a/drivers/usb/dwc3/host.c
>> +++ b/drivers/usb/dwc3/host.c
>> @@ -220,6 +220,7 @@ int dwc3_host_init(struct dwc3 *dwc)
>>   	platform_device_put(xhci);
>>   	return ret;
>>   }
>> +EXPORT_SYMBOL_GPL(dwc3_host_init);
>>   
>>   void dwc3_host_exit(struct dwc3 *dwc)
>>   {
>> @@ -230,3 +231,4 @@ void dwc3_host_exit(struct dwc3 *dwc)
>>   	platform_device_unregister(dwc->xhci);
>>   	dwc->xhci = NULL;
>>   }
>> +EXPORT_SYMBOL_GPL(dwc3_host_exit);
>>
>> -- 
>> 2.34.1
>>
>>
> 
> Thanks for the documentations!
> 
> Please rebase against Greg's usb-testing branch. I think there is
> conflict.

Yup, there's a (small) conflict. I'll rebase the series.

And thanks again for the review! This looks much better than my original 
approach now.


Best,


Sven