[PATCH] configs: am62x_evm_*: Fix USB DFU configuration

[Siddharth Vadapalli]

On Tue, Dec 03, 2024 at 10:40:29PM +0200, Roger Quadros wrote:

Hello Roger,

> CONFIG_USB_XHCI_DWC3 is not required for AM62x as the XHCI
> driver is registered through the dwc3-generic driver.
> 
> CONFIG_USB_XHCI_DWC3 causes problems by hijacking the
> USB controller even if it is not set for Host mode in
> device tree.
> 
> 'dm tree' output after 'usb start' is fixed from
> 
>  simple_bus    5  [ + ]   dwc3-am62             |   |-- dwc3-usb at f900000
>  usb_gadget    0  [   ]   dwc3-generic-periphe  |   |   |-- usb at 31000000
>  usb           0  [ + ]   xhci-dwc3             |   |   `-- usb at 31000000
>  usb_hub       0  [ + ]   usb_hub               |   |       `-- usb_hub
>  simple_bus    6  [ + ]   dwc3-am62             |   |-- dwc3-usb at f910000
>  usb           1  [ + ]   dwc3-generic-host     |   |   |-- usb at 31100000
>  usb_hub       1  [ + ]   usb_hub               |   |   |   `-- usb_hub
>  usb           1  [ + ]   xhci-dwc3             |   |   `-- usb at 31100000
>  usb_hub       2  [ + ]   usb_hub               |   |       `-- usb_hub
> 
> [notice that 'xhci-dwc3' and 'usb_hub' drivers are probed
>  for both USB instances although the first instance
>  is supposed to be 'peripheral' only]
> 
> to
> 
>  simple_bus    5  [   ]   dwc3-am62             |   |-- dwc3-usb at f900000
>  usb_gadget    0  [   ]   dwc3-generic-periphe  |   |   `-- usb at 31000000
>  simple_bus    6  [ + ]   dwc3-am62             |   |-- dwc3-usb at f910000
>  usb           1  [ + ]   dwc3-generic-host     |   |   `-- usb at 31100000
>  usb_hub       0  [ + ]   usb_hub               |   |       `-- usb_hub

While this fixes the issue, I am wondering if the issue lies elsewhere.
In U-Boot, the compatible "snps,dwc3" is associated with:
drivers/usb/host/xhci-dwc3.c
while in Linux, the compatible "snps,dwc3" is associated with:
drivers/usb/dwc3/core.c

So there seem to be two alternatives that I could think of:
1. Modify U-Boot to match Linux in the sense that we associate
"snps,dwc3" with drivers/usb/dwc3/core.c in U-Boot.
2. With the understanding that "dr_mode" doesn't have to be host/otg for
the compatible "snps,dwc3" which is tied to drivers/usb/host/xhci-dwc3.c,
do the following to exit probe when "dr_mode" is "peripheral":
-------------------------------------------------------------------------
diff --git a/drivers/usb/host/xhci-dwc3.c b/drivers/usb/host/xhci-dwc3.c
index e3e0ceff43e..edfd7b97a73 100644
--- a/drivers/usb/host/xhci-dwc3.c
+++ b/drivers/usb/host/xhci-dwc3.c
@@ -208,6 +208,8 @@ static int xhci_dwc3_probe(struct udevice *dev)
        writel(reg, &dwc3_reg->g_usb2phycfg[0]);

        dr_mode = usb_get_dr_mode(dev_ofnode(dev));
+       if (dr_mode == USB_DR_MODE_PERIPHERAL)
+               return -ENODEV;
        if (dr_mode == USB_DR_MODE_OTG &&
            dev_read_bool(dev, "usb-role-switch")) {
                dr_mode = usb_get_role_switch_default_mode(dev_ofnode(dev));
-------------------------------------------------------------------------
which will still show "xhci-dwc3" in the output of "dm tree" after "usb
start", but the driver won't be probed (absence of "+" in the "Probed"
column of "dm tree" output).

I just wanted to point this out as a possible fix for other scenarios.
Disabling "CONFIG_USB_XHCI_DWC3" seems to be the best choice in the
current scenario (i.e. it shouldn't have been set in "USB DFU" fragment
to begin with).

> 
> Fixes: dfc2dff5a844 ("configs: am62x_evm_*: Enable USB and DFU support")
> Signed-off-by: Roger Quadros <rogerq at kernel.org>

Reviewed-by: Siddharth Vadapalli <s-vadapalli at ti.com>

> ---
>  configs/am62x_a53_usbdfu.config | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/configs/am62x_a53_usbdfu.config b/configs/am62x_a53_usbdfu.config
> index 3a19cf23287..0d3c6df1e73 100644
> --- a/configs/am62x_a53_usbdfu.config
> +++ b/configs/am62x_a53_usbdfu.config
> @@ -16,7 +16,6 @@ CONFIG_USB=y
>  CONFIG_DM_USB_GADGET=y
>  CONFIG_SPL_DM_USB_GADGET=y
>  CONFIG_USB_XHCI_HCD=y
> -CONFIG_USB_XHCI_DWC3=y
>  CONFIG_USB_DWC3=y
>  CONFIG_USB_DWC3_GENERIC=y
>  CONFIG_SPL_USB_DWC3_GENERIC=y
> 
> ---
> base-commit: 3073246d1be682071d8b3d07d06c2484907aed60
> change-id: 20241203-am62-usb-xhci-be62bc9584c9
> 
> Best regards,
> -- 
> Roger Quadros <rogerq at kernel.org>
>