[PATCH] usb: cdns3: attempt to fix Kconfig dependencies

[PATCH] usb: cdns3: attempt to fix Kconfig dependencies

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

The way that dependencies between host and gadget mode, as well as cdns3
and cdnsp were handled was rather fragile before commit 6076388ca1ed
("usb: cdns3: Add USBSSP platform driver support").

After those changes, I get randconfig build failures:

arm-linux-gnueabi-ld: drivers/usb/cdns3/cdnsp-gadget.o: in function `__cdnsp_gadget_init':
cdnsp-gadget.c:(.text+0x12da): undefined reference to `cdns_drd_gadget_on'
arm-linux-gnueabi-ld: drivers/usb/cdns3/cdnsp-gadget.o: in function `cdnsp_gadget_pullup':
cdnsp-gadget.c:(.text+0x3030): undefined reference to `cdns_clear_vbus'
arm-linux-gnueabi-ld: cdnsp-gadget.c:(.text+0x3138): undefined reference to `cdns_set_vbus'
arm-linux-gnueabi-ld: drivers/usb/cdns3/cdnsp-gadget.o: in function `cdnsp_gadget_exit':
cdnsp-gadget.c:(.text+0xe0): undefined reference to `cdns_drd_gadget_off'

and I see additional configurations that are broken. The main problem
here is that the 'common' module links against both host and gadget
support if they are enabled, but there are insufficient protections
agains it being built-in if only one of them is built-in and the other
is in a loadable module, causing link failures.

The use of IS_REACHABLE() in gadget-export.h works around a similar
problem if one of cdns3 and cdnsp is built-in but the other one is
=m. This one is worse because instead of a clear link failure, the
logic just makes it not work at all despite support being enabled.

To improve this mess, throw out both the Makefile hacks and the
IS_REACHABLE() hack and replace these with regular Kconfig dependencies
that ensure each driver is only enabled when its dependencies are there,
as we do in most other drivers. The main downside here is that there is no
good way to have built-in gadget support on cdn3 along with USB=m. Fixing
this part proper would require cleaning up the code to turn the 'common'
parts into a library module that only gets called by the other drivers
but does not interact with either host or gadget support itself.

Another problem that is not solved by this patch is the way that
platform specific glue logic in this driver relies on having
a soc specific device as the parent of a generic child, instead of
the specific driver just calling into a common helper module.
This may be impossible to fix without breaking the DT bindings.

Fixes: 6076388ca1ed ("usb: cdns3: Add USBSSP platform driver support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
TBH, I would be more comfortable with reverting 6076388ca1ed altogether
and asking for a new version with the proper fixups included along
with more testing for the next merge window.

My patch has seen some fairly light build testing at this point and
is clearly an improvement over what is in linux-next, but there is
still a risk that I missed some other corner cases.
---
 drivers/usb/cdns3/Kconfig         | 26 +++++++++++++++++++++-----
 drivers/usb/cdns3/Makefile        | 17 +++++------------
 drivers/usb/cdns3/gadget-export.h |  4 ++--
 3 files changed, 28 insertions(+), 19 deletions(-)

diff --git a/drivers/usb/cdns3/Kconfig b/drivers/usb/cdns3/Kconfig
index 97fa84dddbca..07ed694e10b8 100644
--- a/drivers/usb/cdns3/Kconfig
+++ b/drivers/usb/cdns3/Kconfig
@@ -1,6 +1,7 @@
 config USB_CDNS_SUPPORT
 	tristate "Cadence USB Support"
 	depends on USB_SUPPORT && (USB || USB_GADGET) && HAS_DMA
+	depends on USB || !USB
 	select USB_XHCI_PLATFORM if USB_XHCI_HCD
 	select USB_ROLE_SWITCH
 	help
@@ -10,12 +11,24 @@ config USB_CDNS_SUPPORT
 
 config USB_CDNS_HOST
 	bool
+	depends on USB=y || USB=USB_CDNS_SUPPORT
+
+config CONFIG_USB_CDNS_PLATFORM
+	tristate "Cadence USB3 generic platform support"
+	depends on USB_CDNSP || USB_CDNS3
+	depends on USB_CDNSP || !USB_CDNSP
+	depends on USB_CDNS3 || !USB_CDNS3
+	help
+	  The platform driver support is needed on any SoC integrating
+	  a variant of the Cadence USB3 or USBSSP dual-role controllers,
+	  e.g. the TI K3 or NXP i.MX series of SoCs.
 
 if USB_CDNS_SUPPORT
 
 config USB_CDNS3
 	tristate "Cadence USB3 Dual-Role Controller"
 	depends on USB_CDNS_SUPPORT
+	select USB_CDNS_HOST if USB_CDNS3_HOST
 	help
 	  Say Y here if your system has a Cadence USB3 dual-role controller.
 	  It supports: dual-role switch, Host-only, and Peripheral-only.
@@ -23,8 +36,9 @@ config USB_CDNS3
 if USB_CDNS3
 
 config USB_CDNS3_GADGET
-	bool "Cadence USB3 device controller"
+	tristate "Cadence USB3 device controller"
 	depends on USB_GADGET=y || USB_GADGET=USB_CDNS3
+	depends on USB_CDNS_SUPPORT
 	help
 	  Say Y here to enable device controller functionality of the
 	  Cadence USBSS-DEV driver.
@@ -34,8 +48,7 @@ config USB_CDNS3_GADGET
 
 config USB_CDNS3_HOST
 	bool "Cadence USB3 host controller"
-	depends on USB=y || USB=USB_CDNS3
-	select USB_CDNS_HOST
+	depends on USB=y || USB=USB_CDNS_SUPPORT
 	help
 	  Say Y here to enable host controller functionality of the
 	  Cadence driver.
@@ -57,6 +70,7 @@ config USB_CDNS3_PCI_WRAP
 config USB_CDNS3_TI
 	tristate "Cadence USB3 support on TI platforms"
 	depends on ARCH_K3 || COMPILE_TEST
+	depends on USB_CDNS_PLATFORM
 	default USB_CDNS3
 	help
 	  Say 'Y' or 'M' here if you are building for Texas Instruments
@@ -67,6 +81,7 @@ config USB_CDNS3_TI
 config USB_CDNS3_IMX
 	tristate "Cadence USB3 support on NXP i.MX platforms"
 	depends on ARCH_MXC || COMPILE_TEST
+	depends on USB_CDNS_PLATFORM
 	default USB_CDNS3
 	help
 	  Say 'Y' or 'M' here if you are building for NXP i.MX
@@ -77,6 +92,7 @@ config USB_CDNS3_IMX
 config USB_CDNS3_STARFIVE
 	tristate "Cadence USB3 support on StarFive SoC platforms"
 	depends on ARCH_STARFIVE || COMPILE_TEST
+	depends on USB_CDNS_PLATFORM
 	help
 	  Say 'Y' or 'M' here if you are building for StarFive SoCs
 	  platforms that contain Cadence USB3 controller core.
@@ -91,6 +107,7 @@ endif # USB_CDNS3
 config USB_CDNSP
 	tristate "Cadence USBSSP Dual-Role Controller"
 	depends on USB_CDNS_SUPPORT
+	select USB_CDNS_HOST if USB_CDNSP_HOST
 	help
 	  Say Y here if your system has a Cadence USBSSP dual-role controller.
 	  It supports: dual-role switch, Host-only, and Peripheral-only.
@@ -115,8 +132,7 @@ config USB_CDNSP_GADGET
 
 config USB_CDNSP_HOST
 	bool "Cadence USBSSP host controller"
-	depends on USB=y || USB=USB_CDNSP
-	select USB_CDNS_HOST
+	depends on USB=y || USB=USB_CDNS_SUPPORT
 	help
 	  Say Y here to enable host controller functionality of the
 	  Cadence driver.
diff --git a/drivers/usb/cdns3/Makefile b/drivers/usb/cdns3/Makefile
index 63484f145bb9..f1e00ab3d729 100644
--- a/drivers/usb/cdns3/Makefile
+++ b/drivers/usb/cdns3/Makefile
@@ -5,32 +5,25 @@ CFLAGS_cdnsp-trace.o				:= -I$(src)
 
 cdns-usb-common-y				:= core.o drd.o
 
-ifeq ($(CONFIG_USB),m)
-obj-m						+= cdns-usb-common.o
-obj-m						+= cdns3-plat.o
-else
 obj-$(CONFIG_USB_CDNS_SUPPORT)			+= cdns-usb-common.o
-obj-$(CONFIG_USB_CDNS_SUPPORT)			+= cdns3-plat.o
-endif
+
+obj-$(CONFIG_USB_CDNS_PLATFORM)			+= cdns3-plat.o
 
 cdns-usb-common-$(CONFIG_USB_CDNS_HOST) 	+= host.o
 
 # For CDNS3 gadget
-ifneq ($(CONFIG_USB_CDNS3_GADGET),)
 cdns3-y						:= cdns3-gadget.o cdns3-ep0.o
 cdns3-$(CONFIG_TRACING)				+= cdns3-trace.o
-obj-$(CONFIG_USB_CDNS3)				+= cdns3.o
-endif
+obj-$(CONFIG_USB_CDNS3_GADGET)			+= cdns3.o
+
 obj-$(CONFIG_USB_CDNS3_PCI_WRAP)		+= cdns3-pci-wrap.o
 obj-$(CONFIG_USB_CDNS3_TI)			+= cdns3-ti.o
 obj-$(CONFIG_USB_CDNS3_IMX)			+= cdns3-imx.o
 obj-$(CONFIG_USB_CDNS3_STARFIVE)		+= cdns3-starfive.o
 
 # For CDNSP gadget
-ifneq ($(CONFIG_USB_CDNSP_GADGET),)
 cdnsp-y						:= cdnsp-ring.o cdnsp-gadget.o \
 						   cdnsp-mem.o cdnsp-ep0.o
 cdnsp-$(CONFIG_TRACING)				+= cdnsp-trace.o
-obj-$(CONFIG_USB_CDNSP)				+= cdnsp.o
-endif
+obj-$(CONFIG_USB_CDNSP_GADGET)			+= cdnsp.o
 obj-$(CONFIG_USB_CDNSP_PCI)			+= cdnsp-pci.o
diff --git a/drivers/usb/cdns3/gadget-export.h b/drivers/usb/cdns3/gadget-export.h
index 0cb600e2b5d2..c37b6269b001 100644
--- a/drivers/usb/cdns3/gadget-export.h
+++ b/drivers/usb/cdns3/gadget-export.h
@@ -10,7 +10,7 @@
 #ifndef __LINUX_CDNS3_GADGET_EXPORT
 #define __LINUX_CDNS3_GADGET_EXPORT
 
-#if defined(CONFIG_USB_CDNSP_GADGET) && IS_REACHABLE(CONFIG_USB_CDNSP)
+#if IS_ENABLED(CONFIG_USB_CDNSP_GADGET)
 
 int cdnsp_gadget_init(struct cdns *cdns);
 #else
@@ -22,7 +22,7 @@ static inline int cdnsp_gadget_init(struct cdns *cdns)
 
 #endif /* CONFIG_USB_CDNSP_GADGET */
 
-#if defined(CONFIG_USB_CDNS3_GADGET) && IS_REACHABLE(CONFIG_USB_CDNS3)
+#if IS_ENABLED(CONFIG_USB_CDNS3_GADGET)
 
 int cdns3_gadget_init(struct cdns *cdns);
 #else
-- 
2.39.5

Re: [PATCH] usb: cdns3: attempt to fix Kconfig dependencies

[Arnd Bergmann]

On Thu, Apr 2, 2026, at 16:09, Arnd Bergmann wrote:
>
> My patch has seen some fairly light build testing at this point and
> is clearly an improvement over what is in linux-next, but there is
> still a risk that I missed some other corner cases.

This is one change I missed:

diff --git a/drivers/usb/cdns3/Kconfig b/drivers/usb/cdns3/Kconfig
index 07ed694e10b8..ea87ac22f7cf 100644
--- a/drivers/usb/cdns3/Kconfig
+++ b/drivers/usb/cdns3/Kconfig
@@ -118,7 +118,7 @@ config USB_CDNSP
 if USB_CDNSP
 
 config USB_CDNSP_GADGET
-       bool "Cadence USBSSP device controller"
+       tristate "Cadence USBSSP device controller"
        depends on USB_GADGET=y || USB_GADGET=USB_CDNSP
        help
          Say Y here to enable device controller functionality of the

I'll wait for other comments or build failures before resending
the updated patch.

     Arnd

Re: [PATCH] usb: cdns3: attempt to fix Kconfig dependencies

[Peter Chen (CIX)]

On 26-04-02 16:09:55, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> The way that dependencies between host and gadget mode, as well as cdns3
> and cdnsp were handled was rather fragile before commit 6076388ca1ed
> ("usb: cdns3: Add USBSSP platform driver support").
> 
> After those changes, I get randconfig build failures:
> 
> arm-linux-gnueabi-ld: drivers/usb/cdns3/cdnsp-gadget.o: in function `__cdnsp_gadget_init':
> cdnsp-gadget.c:(.text+0x12da): undefined reference to `cdns_drd_gadget_on'
> arm-linux-gnueabi-ld: drivers/usb/cdns3/cdnsp-gadget.o: in function `cdnsp_gadget_pullup':
> cdnsp-gadget.c:(.text+0x3030): undefined reference to `cdns_clear_vbus'
> arm-linux-gnueabi-ld: cdnsp-gadget.c:(.text+0x3138): undefined reference to `cdns_set_vbus'
> arm-linux-gnueabi-ld: drivers/usb/cdns3/cdnsp-gadget.o: in function `cdnsp_gadget_exit':
> cdnsp-gadget.c:(.text+0xe0): undefined reference to `cdns_drd_gadget_off'
> 
> and I see additional configurations that are broken. The main problem
> here is that the 'common' module links against both host and gadget
> support if they are enabled, but there are insufficient protections
> agains it being built-in if only one of them is built-in and the other
> is in a loadable module, causing link failures.
> 
> The use of IS_REACHABLE() in gadget-export.h works around a similar
> problem if one of cdns3 and cdnsp is built-in but the other one is
> =m. This one is worse because instead of a clear link failure, the
> logic just makes it not work at all despite support being enabled.
> 
> To improve this mess, throw out both the Makefile hacks and the
> IS_REACHABLE() hack and replace these with regular Kconfig dependencies
> that ensure each driver is only enabled when its dependencies are there,
> as we do in most other drivers. The main downside here is that there is no
> good way to have built-in gadget support on cdn3 along with USB=m. Fixing
> this part proper would require cleaning up the code to turn the 'common'
> parts into a library module that only gets called by the other drivers
> but does not interact with either host or gadget support itself.
> 
> Another problem that is not solved by this patch is the way that
> platform specific glue logic in this driver relies on having
> a soc specific device as the parent of a generic child, instead of
> the specific driver just calling into a common helper module.
> This may be impossible to fix without breaking the DT bindings.
> 
> Fixes: 6076388ca1ed ("usb: cdns3: Add USBSSP platform driver support")

Hi Arnd,

Thanks for fixing it, I am sorry for taking your effort debug it.

> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> TBH, I would be more comfortable with reverting 6076388ca1ed altogether
> and asking for a new version with the proper fixups included along
> with more testing for the next merge window.

It depends on Greg, I am okay for both ways. If Greg reverts the patch,
I will do below improvements and adapts for most of your changes for v3
patch.

cdns-usb-common.ko is a libary, and no USB/GADGET dependency, could builds in.
  ├── core.o  
  └── drd.o

cdns3-host.ko     -> depends on USB/XHCI（it is m when USB = m
cdns3.ko (gadget) -> depends on USB_GADGET
cdnsp.ko (gadget) -> depends on USB_GADGET
cdns3-plat.ko     -> assign host_init/gadget_init function pointer

In that way, below combination could work:
cdns-usb-common=y
cdns3-host=m
cdns3(p)-gadget=y

> @@ -10,12 +11,24 @@ config USB_CDNS_SUPPORT
>  
>  config USB_CDNS_HOST
>  	bool
> +	depends on USB=y || USB=USB_CDNS_SUPPORT
> +
> +config CONFIG_USB_CDNS_PLATFORM

%s/CONFIG_USB_CDNS_PLATFORM/USB_CDNS_PLATFORM

Peter

> +	tristate "Cadence USB3 generic platform support"
> +	depends on USB_CDNSP || USB_CDNS3
> +	depends on USB_CDNSP || !USB_CDNSP
> +	depends on USB_CDNS3 || !USB_CDNS3
> +	help
> +	  The platform driver support is needed on any SoC integrating
> +	  a variant of the Cadence USB3 or USBSSP dual-role controllers,
> +	  e.g. the TI K3 or NXP i.MX series of SoCs.
>  
>  if USB_CDNS_SUPPORT
>  
>  config USB_CDNS3
>  	tristate "Cadence USB3 Dual-Role Controller"
>  	depends on USB_CDNS_SUPPORT
> +	select USB_CDNS_HOST if USB_CDNS3_HOST
>  	help
>  	  Say Y here if your system has a Cadence USB3 dual-role controller.
>  	  It supports: dual-role switch, Host-only, and Peripheral-only.
> @@ -23,8 +36,9 @@ config USB_CDNS3
>  if USB_CDNS3
>  
>  config USB_CDNS3_GADGET
> -	bool "Cadence USB3 device controller"
> +	tristate "Cadence USB3 device controller"
>  	depends on USB_GADGET=y || USB_GADGET=USB_CDNS3
> +	depends on USB_CDNS_SUPPORT
>  	help
>  	  Say Y here to enable device controller functionality of the
>  	  Cadence USBSS-DEV driver.
> @@ -34,8 +48,7 @@ config USB_CDNS3_GADGET
>  
>  config USB_CDNS3_HOST
>  	bool "Cadence USB3 host controller"
> -	depends on USB=y || USB=USB_CDNS3
> -	select USB_CDNS_HOST
> +	depends on USB=y || USB=USB_CDNS_SUPPORT
>  	help
>  	  Say Y here to enable host controller functionality of the
>  	  Cadence driver.
> @@ -57,6 +70,7 @@ config USB_CDNS3_PCI_WRAP
>  config USB_CDNS3_TI
>  	tristate "Cadence USB3 support on TI platforms"
>  	depends on ARCH_K3 || COMPILE_TEST
> +	depends on USB_CDNS_PLATFORM
>  	default USB_CDNS3
>  	help
>  	  Say 'Y' or 'M' here if you are building for Texas Instruments
> @@ -67,6 +81,7 @@ config USB_CDNS3_TI
>  config USB_CDNS3_IMX
>  	tristate "Cadence USB3 support on NXP i.MX platforms"
>  	depends on ARCH_MXC || COMPILE_TEST
> +	depends on USB_CDNS_PLATFORM
>  	default USB_CDNS3
>  	help
>  	  Say 'Y' or 'M' here if you are building for NXP i.MX
> @@ -77,6 +92,7 @@ config USB_CDNS3_IMX
>  config USB_CDNS3_STARFIVE
>  	tristate "Cadence USB3 support on StarFive SoC platforms"
>  	depends on ARCH_STARFIVE || COMPILE_TEST
> +	depends on USB_CDNS_PLATFORM
>  	help
>  	  Say 'Y' or 'M' here if you are building for StarFive SoCs
>  	  platforms that contain Cadence USB3 controller core.
> @@ -91,6 +107,7 @@ endif # USB_CDNS3
>  config USB_CDNSP
>  	tristate "Cadence USBSSP Dual-Role Controller"
>  	depends on USB_CDNS_SUPPORT
> +	select USB_CDNS_HOST if USB_CDNSP_HOST
>  	help
>  	  Say Y here if your system has a Cadence USBSSP dual-role controller.
>  	  It supports: dual-role switch, Host-only, and Peripheral-only.
> @@ -115,8 +132,7 @@ config USB_CDNSP_GADGET
>  
>  config USB_CDNSP_HOST
>  	bool "Cadence USBSSP host controller"
> -	depends on USB=y || USB=USB_CDNSP
> -	select USB_CDNS_HOST
> +	depends on USB=y || USB=USB_CDNS_SUPPORT
>  	help
>  	  Say Y here to enable host controller functionality of the
>  	  Cadence driver.
> diff --git a/drivers/usb/cdns3/Makefile b/drivers/usb/cdns3/Makefile
> index 63484f145bb9..f1e00ab3d729 100644
> --- a/drivers/usb/cdns3/Makefile
> +++ b/drivers/usb/cdns3/Makefile
> @@ -5,32 +5,25 @@ CFLAGS_cdnsp-trace.o				:= -I$(src)
>  
>  cdns-usb-common-y				:= core.o drd.o
>  
> -ifeq ($(CONFIG_USB),m)
> -obj-m						+= cdns-usb-common.o
> -obj-m						+= cdns3-plat.o
> -else
>  obj-$(CONFIG_USB_CDNS_SUPPORT)			+= cdns-usb-common.o
> -obj-$(CONFIG_USB_CDNS_SUPPORT)			+= cdns3-plat.o
> -endif
> +
> +obj-$(CONFIG_USB_CDNS_PLATFORM)			+= cdns3-plat.o
>  
>  cdns-usb-common-$(CONFIG_USB_CDNS_HOST) 	+= host.o
>  
>  # For CDNS3 gadget
> -ifneq ($(CONFIG_USB_CDNS3_GADGET),)
>  cdns3-y						:= cdns3-gadget.o cdns3-ep0.o
>  cdns3-$(CONFIG_TRACING)				+= cdns3-trace.o
> -obj-$(CONFIG_USB_CDNS3)				+= cdns3.o
> -endif
> +obj-$(CONFIG_USB_CDNS3_GADGET)			+= cdns3.o
> +
>  obj-$(CONFIG_USB_CDNS3_PCI_WRAP)		+= cdns3-pci-wrap.o
>  obj-$(CONFIG_USB_CDNS3_TI)			+= cdns3-ti.o
>  obj-$(CONFIG_USB_CDNS3_IMX)			+= cdns3-imx.o
>  obj-$(CONFIG_USB_CDNS3_STARFIVE)		+= cdns3-starfive.o
>  
>  # For CDNSP gadget
> -ifneq ($(CONFIG_USB_CDNSP_GADGET),)
>  cdnsp-y						:= cdnsp-ring.o cdnsp-gadget.o \
>  						   cdnsp-mem.o cdnsp-ep0.o
>  cdnsp-$(CONFIG_TRACING)				+= cdnsp-trace.o
> -obj-$(CONFIG_USB_CDNSP)				+= cdnsp.o
> -endif
> +obj-$(CONFIG_USB_CDNSP_GADGET)			+= cdnsp.o
>  obj-$(CONFIG_USB_CDNSP_PCI)			+= cdnsp-pci.o
> diff --git a/drivers/usb/cdns3/gadget-export.h b/drivers/usb/cdns3/gadget-export.h
> index 0cb600e2b5d2..c37b6269b001 100644
> --- a/drivers/usb/cdns3/gadget-export.h
> +++ b/drivers/usb/cdns3/gadget-export.h
> @@ -10,7 +10,7 @@
>  #ifndef __LINUX_CDNS3_GADGET_EXPORT
>  #define __LINUX_CDNS3_GADGET_EXPORT
>  
> -#if defined(CONFIG_USB_CDNSP_GADGET) && IS_REACHABLE(CONFIG_USB_CDNSP)
> +#if IS_ENABLED(CONFIG_USB_CDNSP_GADGET)
>  
>  int cdnsp_gadget_init(struct cdns *cdns);
>  #else
> @@ -22,7 +22,7 @@ static inline int cdnsp_gadget_init(struct cdns *cdns)
>  
>  #endif /* CONFIG_USB_CDNSP_GADGET */
>  
> -#if defined(CONFIG_USB_CDNS3_GADGET) && IS_REACHABLE(CONFIG_USB_CDNS3)
> +#if IS_ENABLED(CONFIG_USB_CDNS3_GADGET)
>  
>  int cdns3_gadget_init(struct cdns *cdns);
>  #else
> -- 
> 2.39.5
> 

-- 

Best regards,
Peter

Re: [PATCH] usb: cdns3: attempt to fix Kconfig dependencies

[Arnd Bergmann]

On Fri, Apr 3, 2026, at 09:50, Peter Chen (CIX) wrote:
> On 26-04-02 16:09:55, Arnd Bergmann wrote:
>> ---
>> TBH, I would be more comfortable with reverting 6076388ca1ed altogether
>> and asking for a new version with the proper fixups included along
>> with more testing for the next merge window.
>
> It depends on Greg, I am okay for both ways. If Greg reverts the patch,
> I will do below improvements and adapts for most of your changes for v3
> patch.
>
> cdns-usb-common.ko is a libary, and no USB/GADGET dependency, could builds in.
>   ├── core.o  
>   └── drd.o
>
> cdns3-host.ko     -> depends on USB/XHCI（it is m when USB = m
> cdns3.ko (gadget) -> depends on USB_GADGET
> cdnsp.ko (gadget) -> depends on USB_GADGET
> cdns3-plat.ko     -> assign host_init/gadget_init function pointer

This all sounds good. Ideally cdns3-plat.ko would also lose the
dependency on cdns3.ko/cdnsp.ko

>> @@ -10,12 +11,24 @@ config USB_CDNS_SUPPORT
>>  
>>  config USB_CDNS_HOST
>>  	bool
>> +	depends on USB=y || USB=USB_CDNS_SUPPORT
>> +
>> +config CONFIG_USB_CDNS_PLATFORM
>
> %s/CONFIG_USB_CDNS_PLATFORM/USB_CDNS_PLATFORM

Oh, this means my patch did not actually work at all, and my testing
was pointless. I've fixed that now in my randconfig tree to see
if anything else comes up.

     Arnd

Re: [PATCH] usb: cdns3: attempt to fix Kconfig dependencies

[Greg Kroah-Hartman]

On Fri, Apr 03, 2026 at 03:50:45PM +0800, Peter Chen (CIX) wrote:
> On 26-04-02 16:09:55, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@arndb.de>
> > 
> > The way that dependencies between host and gadget mode, as well as cdns3
> > and cdnsp were handled was rather fragile before commit 6076388ca1ed
> > ("usb: cdns3: Add USBSSP platform driver support").
> > 
> > After those changes, I get randconfig build failures:
> > 
> > arm-linux-gnueabi-ld: drivers/usb/cdns3/cdnsp-gadget.o: in function `__cdnsp_gadget_init':
> > cdnsp-gadget.c:(.text+0x12da): undefined reference to `cdns_drd_gadget_on'
> > arm-linux-gnueabi-ld: drivers/usb/cdns3/cdnsp-gadget.o: in function `cdnsp_gadget_pullup':
> > cdnsp-gadget.c:(.text+0x3030): undefined reference to `cdns_clear_vbus'
> > arm-linux-gnueabi-ld: cdnsp-gadget.c:(.text+0x3138): undefined reference to `cdns_set_vbus'
> > arm-linux-gnueabi-ld: drivers/usb/cdns3/cdnsp-gadget.o: in function `cdnsp_gadget_exit':
> > cdnsp-gadget.c:(.text+0xe0): undefined reference to `cdns_drd_gadget_off'
> > 
> > and I see additional configurations that are broken. The main problem
> > here is that the 'common' module links against both host and gadget
> > support if they are enabled, but there are insufficient protections
> > agains it being built-in if only one of them is built-in and the other
> > is in a loadable module, causing link failures.
> > 
> > The use of IS_REACHABLE() in gadget-export.h works around a similar
> > problem if one of cdns3 and cdnsp is built-in but the other one is
> > =m. This one is worse because instead of a clear link failure, the
> > logic just makes it not work at all despite support being enabled.
> > 
> > To improve this mess, throw out both the Makefile hacks and the
> > IS_REACHABLE() hack and replace these with regular Kconfig dependencies
> > that ensure each driver is only enabled when its dependencies are there,
> > as we do in most other drivers. The main downside here is that there is no
> > good way to have built-in gadget support on cdn3 along with USB=m. Fixing
> > this part proper would require cleaning up the code to turn the 'common'
> > parts into a library module that only gets called by the other drivers
> > but does not interact with either host or gadget support itself.
> > 
> > Another problem that is not solved by this patch is the way that
> > platform specific glue logic in this driver relies on having
> > a soc specific device as the parent of a generic child, instead of
> > the specific driver just calling into a common helper module.
> > This may be impossible to fix without breaking the DT bindings.
> > 
> > Fixes: 6076388ca1ed ("usb: cdns3: Add USBSSP platform driver support")
> 
> Hi Arnd,
> 
> Thanks for fixing it, I am sorry for taking your effort debug it.
> 
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > ---
> > TBH, I would be more comfortable with reverting 6076388ca1ed altogether
> > and asking for a new version with the proper fixups included along
> > with more testing for the next merge window.
> 
> It depends on Greg, I am okay for both ways. If Greg reverts the patch,
> I will do below improvements and adapts for most of your changes for v3
> patch.

I'll be glad to revert if you want me to, just let me know.

thanks,

greg k-h

Re: [PATCH] usb: cdns3: attempt to fix Kconfig dependencies

[Peter Chen (CIX)]

On 26-04-03 10:39:18, Arnd Bergmann wrote:
> On Fri, Apr 3, 2026, at 09:50, Peter Chen (CIX) wrote:
> > On 26-04-02 16:09:55, Arnd Bergmann wrote:
> >> ---
> >> TBH, I would be more comfortable with reverting 6076388ca1ed altogether
> >> and asking for a new version with the proper fixups included along
> >> with more testing for the next merge window.
> >
> > It depends on Greg, I am okay for both ways. If Greg reverts the patch,
> > I will do below improvements and adapts for most of your changes for v3
> > patch.
> >
> > cdns-usb-common.ko is a libary, and no USB/GADGET dependency, could builds in.
> >   ├── core.o  
> >   └── drd.o
> >
> > cdns3-host.ko     -> depends on USB/XHCI（it is m when USB = m
> > cdns3.ko (gadget) -> depends on USB_GADGET
> > cdnsp.ko (gadget) -> depends on USB_GADGET
> > cdns3-plat.ko     -> assign host_init/gadget_init function pointer
> 
> This all sounds good. Ideally cdns3-plat.ko would also lose the
> dependency on cdns3.ko/cdnsp.ko

No, it can't. cdns3-plat.ko depends on cdns3.ko/cdsnp.ko or its
stub.

> 
> >> @@ -10,12 +11,24 @@ config USB_CDNS_SUPPORT
> >>  
> >>  config USB_CDNS_HOST
> >>  	bool
> >> +	depends on USB=y || USB=USB_CDNS_SUPPORT
> >> +
> >> +config CONFIG_USB_CDNS_PLATFORM
> >
> > %s/CONFIG_USB_CDNS_PLATFORM/USB_CDNS_PLATFORM
> 
> Oh, this means my patch did not actually work at all, and my testing
> was pointless. I've fixed that now in my randconfig tree to see
> if anything else comes up.
> 
>      Arnd

I am afraid it may need to change more for your patch, otherwise, it could have
error with below combinations:

USB=y USB_GADGET=y USB_CDNS_SUPPORT=y USB_CDNS_HOST=y USB_CDNS_PLATFORM=y USB_CDNS3=y
USB_CDNS3_GADGET=y USB_CDNS3_HOST=y USB_CDNSP=y USB_CDNSP_GADGET=m USB_CDNSP_HOST=y

USB_CDNS_PLATFORM reference to the cdnsp_gadget_init which is built as module.

drivers/usb/cdns3/cdns3-plat.c:52: undefined reference to `cdnsp_gadget_init'

So far, below changes works okay at my test:

diff --git a/drivers/usb/cdns3/Kconfig b/drivers/usb/cdns3/Kconfig
index 07ed694e10b8..57cd7e3b5b22 100644
--- a/drivers/usb/cdns3/Kconfig
+++ b/drivers/usb/cdns3/Kconfig
@@ -13,11 +13,13 @@ config USB_CDNS_HOST
 	bool
 	depends on USB=y || USB=USB_CDNS_SUPPORT
 
-config CONFIG_USB_CDNS_PLATFORM
+config USB_CDNS_PLATFORM
 	tristate "Cadence USB3 generic platform support"
 	depends on USB_CDNSP || USB_CDNS3
 	depends on USB_CDNSP || !USB_CDNSP
 	depends on USB_CDNS3 || !USB_CDNS3
+	depends on USB_CDNS3_GADGET || !USB_CDNS3_GADGET
+	depends on USB_CDNSP_GADGET || !USB_CDNSP_GADGET
 	help
 	  The platform driver support is needed on any SoC integrating
 	  a variant of the Cadence USB3 or USBSSP dual-role controllers,
@@ -118,7 +120,7 @@ config USB_CDNSP
 if USB_CDNSP
 
 config USB_CDNSP_GADGET
-	bool "Cadence USBSSP device controller"
+	tristate "Cadence USBSSP device controller"
 	depends on USB_GADGET=y || USB_GADGET=USB_CDNSP
 	help
 	  Say Y here to enable device controller functionality of the


-- 

Best regards,
Peter

Re: [PATCH] usb: cdns3: attempt to fix Kconfig dependencies

[Peter Chen (CIX)]

On 26-04-03 10:54:44, Greg Kroah-Hartman wrote:
> On Fri, Apr 03, 2026 at 03:50:45PM +0800, Peter Chen (CIX) wrote:
> > On 26-04-02 16:09:55, Arnd Bergmann wrote:
> > > From: Arnd Bergmann <arnd@arndb.de>
> > > 
> > > The way that dependencies between host and gadget mode, as well as cdns3
> > > and cdnsp were handled was rather fragile before commit 6076388ca1ed
> > > ("usb: cdns3: Add USBSSP platform driver support").
> > > 
> > > After those changes, I get randconfig build failures:
> > > 
> > > arm-linux-gnueabi-ld: drivers/usb/cdns3/cdnsp-gadget.o: in function `__cdnsp_gadget_init':
> > > cdnsp-gadget.c:(.text+0x12da): undefined reference to `cdns_drd_gadget_on'
> > > arm-linux-gnueabi-ld: drivers/usb/cdns3/cdnsp-gadget.o: in function `cdnsp_gadget_pullup':
> > > cdnsp-gadget.c:(.text+0x3030): undefined reference to `cdns_clear_vbus'
> > > arm-linux-gnueabi-ld: cdnsp-gadget.c:(.text+0x3138): undefined reference to `cdns_set_vbus'
> > > arm-linux-gnueabi-ld: drivers/usb/cdns3/cdnsp-gadget.o: in function `cdnsp_gadget_exit':
> > > cdnsp-gadget.c:(.text+0xe0): undefined reference to `cdns_drd_gadget_off'
> > > 
> > > and I see additional configurations that are broken. The main problem
> > > here is that the 'common' module links against both host and gadget
> > > support if they are enabled, but there are insufficient protections
> > > agains it being built-in if only one of them is built-in and the other
> > > is in a loadable module, causing link failures.
> > > 
> > > The use of IS_REACHABLE() in gadget-export.h works around a similar
> > > problem if one of cdns3 and cdnsp is built-in but the other one is
> > > =m. This one is worse because instead of a clear link failure, the
> > > logic just makes it not work at all despite support being enabled.
> > > 
> > > To improve this mess, throw out both the Makefile hacks and the
> > > IS_REACHABLE() hack and replace these with regular Kconfig dependencies
> > > that ensure each driver is only enabled when its dependencies are there,
> > > as we do in most other drivers. The main downside here is that there is no
> > > good way to have built-in gadget support on cdn3 along with USB=m. Fixing
> > > this part proper would require cleaning up the code to turn the 'common'
> > > parts into a library module that only gets called by the other drivers
> > > but does not interact with either host or gadget support itself.
> > > 
> > > Another problem that is not solved by this patch is the way that
> > > platform specific glue logic in this driver relies on having
> > > a soc specific device as the parent of a generic child, instead of
> > > the specific driver just calling into a common helper module.
> > > This may be impossible to fix without breaking the DT bindings.
> > > 
> > > Fixes: 6076388ca1ed ("usb: cdns3: Add USBSSP platform driver support")
> > 
> > Hi Arnd,
> > 
> > Thanks for fixing it, I am sorry for taking your effort debug it.
> > 
> > > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > > ---
> > > TBH, I would be more comfortable with reverting 6076388ca1ed altogether
> > > and asking for a new version with the proper fixups included along
> > > with more testing for the next merge window.
> > 
> > It depends on Greg, I am okay for both ways. If Greg reverts the patch,
> > I will do below improvements and adapts for most of your changes for v3
> > patch.
> 
> I'll be glad to revert if you want me to, just let me know.
> 

Thanks, Greg. Please revert below two patches in your usb-next branch:

6076388ca1ed usb: cdns3: Add USBSSP platform driver support
fb14e7f7cbb4 dt-bindings: usb: cdns,usb3: document USBSSP controller support

-- 

Best regards,
Peter

Re: [PATCH] usb: cdns3: attempt to fix Kconfig dependencies

[Greg Kroah-Hartman]

On Fri, Apr 03, 2026 at 05:40:33PM +0800, Peter Chen (CIX) wrote:
> On 26-04-03 10:54:44, Greg Kroah-Hartman wrote:
> > On Fri, Apr 03, 2026 at 03:50:45PM +0800, Peter Chen (CIX) wrote:
> > > On 26-04-02 16:09:55, Arnd Bergmann wrote:
> > > > From: Arnd Bergmann <arnd@arndb.de>
> > > > 
> > > > The way that dependencies between host and gadget mode, as well as cdns3
> > > > and cdnsp were handled was rather fragile before commit 6076388ca1ed
> > > > ("usb: cdns3: Add USBSSP platform driver support").
> > > > 
> > > > After those changes, I get randconfig build failures:
> > > > 
> > > > arm-linux-gnueabi-ld: drivers/usb/cdns3/cdnsp-gadget.o: in function `__cdnsp_gadget_init':
> > > > cdnsp-gadget.c:(.text+0x12da): undefined reference to `cdns_drd_gadget_on'
> > > > arm-linux-gnueabi-ld: drivers/usb/cdns3/cdnsp-gadget.o: in function `cdnsp_gadget_pullup':
> > > > cdnsp-gadget.c:(.text+0x3030): undefined reference to `cdns_clear_vbus'
> > > > arm-linux-gnueabi-ld: cdnsp-gadget.c:(.text+0x3138): undefined reference to `cdns_set_vbus'
> > > > arm-linux-gnueabi-ld: drivers/usb/cdns3/cdnsp-gadget.o: in function `cdnsp_gadget_exit':
> > > > cdnsp-gadget.c:(.text+0xe0): undefined reference to `cdns_drd_gadget_off'
> > > > 
> > > > and I see additional configurations that are broken. The main problem
> > > > here is that the 'common' module links against both host and gadget
> > > > support if they are enabled, but there are insufficient protections
> > > > agains it being built-in if only one of them is built-in and the other
> > > > is in a loadable module, causing link failures.
> > > > 
> > > > The use of IS_REACHABLE() in gadget-export.h works around a similar
> > > > problem if one of cdns3 and cdnsp is built-in but the other one is
> > > > =m. This one is worse because instead of a clear link failure, the
> > > > logic just makes it not work at all despite support being enabled.
> > > > 
> > > > To improve this mess, throw out both the Makefile hacks and the
> > > > IS_REACHABLE() hack and replace these with regular Kconfig dependencies
> > > > that ensure each driver is only enabled when its dependencies are there,
> > > > as we do in most other drivers. The main downside here is that there is no
> > > > good way to have built-in gadget support on cdn3 along with USB=m. Fixing
> > > > this part proper would require cleaning up the code to turn the 'common'
> > > > parts into a library module that only gets called by the other drivers
> > > > but does not interact with either host or gadget support itself.
> > > > 
> > > > Another problem that is not solved by this patch is the way that
> > > > platform specific glue logic in this driver relies on having
> > > > a soc specific device as the parent of a generic child, instead of
> > > > the specific driver just calling into a common helper module.
> > > > This may be impossible to fix without breaking the DT bindings.
> > > > 
> > > > Fixes: 6076388ca1ed ("usb: cdns3: Add USBSSP platform driver support")
> > > 
> > > Hi Arnd,
> > > 
> > > Thanks for fixing it, I am sorry for taking your effort debug it.
> > > 
> > > > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > > > ---
> > > > TBH, I would be more comfortable with reverting 6076388ca1ed altogether
> > > > and asking for a new version with the proper fixups included along
> > > > with more testing for the next merge window.
> > > 
> > > It depends on Greg, I am okay for both ways. If Greg reverts the patch,
> > > I will do below improvements and adapts for most of your changes for v3
> > > patch.
> > 
> > I'll be glad to revert if you want me to, just let me know.
> > 
> 
> Thanks, Greg. Please revert below two patches in your usb-next branch:
> 
> 6076388ca1ed usb: cdns3: Add USBSSP platform driver support
> fb14e7f7cbb4 dt-bindings: usb: cdns,usb3: document USBSSP controller support

Ick, doesn't revert cleanly, I'm going to also have to drop commit
7b7f2dd91382 ("usb: cdnsp: Add support for device-only configuration")
Will go do that now....

greg k-h

Re: [PATCH] usb: cdns3: attempt to fix Kconfig dependencies

[Arnd Bergmann]

On Fri, Apr 3, 2026, at 11:26, Peter Chen (CIX) wrote:
> On 26-04-03 10:39:18, Arnd Bergmann wrote:
>> On Fri, Apr 3, 2026, at 09:50, Peter Chen (CIX) wrote:
>
> I am afraid it may need to change more for your patch, otherwise, it could have
> error with below combinations:
>
> USB=y USB_GADGET=y USB_CDNS_SUPPORT=y USB_CDNS_HOST=y 
> USB_CDNS_PLATFORM=y USB_CDNS3=y
> USB_CDNS3_GADGET=y USB_CDNS3_HOST=y USB_CDNSP=y USB_CDNSP_GADGET=m 
> USB_CDNSP_HOST=y
>
> USB_CDNS_PLATFORM reference to the cdnsp_gadget_init which is built as module.
>
> drivers/usb/cdns3/cdns3-plat.c:52: undefined reference to `cdnsp_gadget_init'

Good catch! I ran into the same one after a few hundred more randonfig
builds and can confirm that your suggested fixup addresses all of the
problems found so far.

> @@ -13,11 +13,13 @@ config USB_CDNS_HOST
>  	bool
>  	depends on USB=y || USB=USB_CDNS_SUPPORT
> 
> -config CONFIG_USB_CDNS_PLATFORM
> +config USB_CDNS_PLATFORM
>  	tristate "Cadence USB3 generic platform support"
>  	depends on USB_CDNSP || USB_CDNS3
>  	depends on USB_CDNSP || !USB_CDNSP
>  	depends on USB_CDNS3 || !USB_CDNS3
> +	depends on USB_CDNS3_GADGET || !USB_CDNS3_GADGET
> +	depends on USB_CDNSP_GADGET || !USB_CDNSP_GADGET
>  	help
>  	  The platform driver support is needed on any SoC integrating
>  	  a variant of the Cadence USB3 or USBSSP dual-role controllers,

The dependencies here are rather unwieldy, but it does look like
this is the minimum set we need with the current code.

The only other alternative I see would be to split up the
platform driver support into separate modules for cdns3 and
cdnsp as well, which would make the dependencies trivial but
require reworking of the actual in a way that I haven't
been able to figure out yet. If you are already integrating
other changes for the next attempt, maybe you can try to
come up with a solution for this as well.

     Arnd

Re: [PATCH] usb: cdns3: attempt to fix Kconfig dependencies

[Peter Chen (CIX)]

On 26-04-03 20:50:52, Arnd Bergmann wrote:
> 
> > @@ -13,11 +13,13 @@ config USB_CDNS_HOST
> >  	bool
> >  	depends on USB=y || USB=USB_CDNS_SUPPORT
> > 
> > -config CONFIG_USB_CDNS_PLATFORM
> > +config USB_CDNS_PLATFORM
> >  	tristate "Cadence USB3 generic platform support"
> >  	depends on USB_CDNSP || USB_CDNS3
> >  	depends on USB_CDNSP || !USB_CDNSP
> >  	depends on USB_CDNS3 || !USB_CDNS3
> > +	depends on USB_CDNS3_GADGET || !USB_CDNS3_GADGET
> > +	depends on USB_CDNSP_GADGET || !USB_CDNSP_GADGET
> >  	help
> >  	  The platform driver support is needed on any SoC integrating
> >  	  a variant of the Cadence USB3 or USBSSP dual-role controllers,
> 
> The dependencies here are rather unwieldy, but it does look like
> this is the minimum set we need with the current code.
> 
> The only other alternative I see would be to split up the
> platform driver support into separate modules for cdns3 and
> cdnsp as well, which would make the dependencies trivial but
> require reworking of the actual in a way that I haven't
> been able to figure out yet. If you are already integrating
> other changes for the next attempt, maybe you can try to
> come up with a solution for this as well.

Thanks for your suggestion, creating different platform driver
between cdns3 and cdnsp is the way we used at downstream, but
when I try to upstream cdsnp platform driver support, I find
the two platforms driver are 95% identical in content, so I
would like to keep one platform driver and one binding doc.

By the way, are there any randconfigs I could run to avoid
the similar break, of course, I will pass my local USB
randconfigs tests?

-- 

Best regards,
Peter