[PATCH v2 4/7] arch: arm: mach-snapdragon: Make USB speed fixup configurable

[Casey Connolly]

Hi Balaji,

On 24/11/2025 16:55, Balaji Selvanathan wrote:
> Add CONFIG_QCOM_USB_FIXUP option to allow platforms to disable
> the USB speed limitation fixup when they have proper super-speed
> USB support in U-Boot.

In general, we prefer to handle cases like this at runtime rather than
compile time. Could you rework this to check for the "qcom,sc7280-dwc3"
compatible and just skip the check in that case? I would also propose
adding a log_warning() in the fixup case so that folks working on other
platforms know to add their compatible too.

Obviously that's still not an ideal solution, maybe it would be possible
to implement the Super Smart (tm) fix and actually check if a driver
/will/ bind to the ss-phy node before the fixup, it depends how slow
that would be.

Kind regards,

> 
> Currently, U-Boot limits USB to high-speed mode on all Qualcomm
> platforms by fixing up the device tree at runtime. This was
> necessary because most platforms lacked super-speed PHY drivers.
> 
> However, newer platforms now have proper QMP PHY drivers that support
> super-speed USB. For these platforms, the fixup is counterproductive
> as it prevents the hardware from operating at its full capability.
> 
> This change:
> - Adds CONFIG_QCOM_USB_FIXUP (default y) to maintain backward
>   compatibility with existing platforms
> - Wraps the fixup code with #ifdef to allow selective disabling
> - Allows platforms with super-speed support to disable the fixup
>   via their defconfig
> 
> Platforms without super-speed PHY drivers will continue to work
> as before with the fixup enabled by default.
> 
> Signed-off-by: Balaji Selvanathan <balaji.selvanathan at oss.qualcomm.com>
> ---
>  arch/arm/mach-snapdragon/Kconfig    | 10 ++++++++++
>  arch/arm/mach-snapdragon/of_fixup.c |  4 ++++
>  2 files changed, 14 insertions(+)
> 
> diff --git a/arch/arm/mach-snapdragon/Kconfig b/arch/arm/mach-snapdragon/Kconfig
> index 976c0e35fce..6c53aeef597 100644
> --- a/arch/arm/mach-snapdragon/Kconfig
> +++ b/arch/arm/mach-snapdragon/Kconfig
> @@ -29,6 +29,16 @@ config SYS_MALLOC_LEN
>  config LNX_KRNL_IMG_TEXT_OFFSET_BASE
>  	default 0x80000000
>  
> +config QCOM_USB_FIXUP
> +	bool "Enable USB speed fixup for Qualcomm platforms"
> +	default y
> +	help
> +	  Enable runtime fixup of USB device tree nodes to limit USB to
> +	  high-speed mode. This is needed on some Qualcomm platforms where
> +	  U-Boot doesn't support super-speed USB.
> +	  Disable this for platforms that have proper super-speed USB support
> +	  in U-Boot.
> +
>  config SYS_BOARD
>  	string "Snapdragon SoCs based board"
>  	help
> diff --git a/arch/arm/mach-snapdragon/of_fixup.c b/arch/arm/mach-snapdragon/of_fixup.c
> index eec2c0c757e..6a64168f67e 100644
> --- a/arch/arm/mach-snapdragon/of_fixup.c
> +++ b/arch/arm/mach-snapdragon/of_fixup.c
> @@ -27,6 +27,7 @@
>  #include <stdlib.h>
>  #include <time.h>
>  
> +#ifdef CONFIG_QCOM_USB_FIXUP
>  /* U-Boot only supports USB high-speed mode on Qualcomm platforms with DWC3
>   * USB controllers. Rather than requiring source level DT changes, we fix up
>   * DT here. This improves compatibility with upstream DT and simplifies the
> @@ -115,6 +116,7 @@ static void fixup_usb_nodes(struct device_node *root)
>  			log_warning("Failed to fixup node %s: %d\n", glue_np->name, ret);
>  	}
>  }
> +#endif
>  
>  /* Remove all references to the rpmhpd device */
>  static void fixup_power_domains(struct device_node *root)
> @@ -157,7 +159,9 @@ static int qcom_of_fixup_nodes(void * __maybe_unused ctx, struct event *event)
>  {
>  	struct device_node *root = event->data.of_live_built.root;
>  
> +#ifdef CONFIG_QCOM_USB_FIXUP
>  	time_call(fixup_usb_nodes, root);
> +#endif
>  	time_call(fixup_power_domains, root);
>  
>  	return 0;

-- 
// Casey (she/her)