Re: [PATCH] usb: xhci-dwc3: Bail out if "dr_mode" is "peripheral"

[Roger Quadros <rogerq@kernel.org>]

Hi Siddharth,

On 06/12/2024 13:04, Siddharth Vadapalli wrote:
> Since the compatible "snps,dwc3" can be specified in the device-tree for
> the Designware USB Controller configured for not only Host and OTG modes
> of operation, but also for Peripheral mode of operation, bail out if
> "dr_mode" is "peripheral".
> 
> Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
> ---
> 
> Hello,
> 
> This patch is based on commit
> 448add55297 Merge branch 'master' of https://source.denx.de/u-boot/custodians/u-boot-pmic
> of the master branch of U-Boot.
> 
> Regards,
> Siddharth.
> 
>  drivers/usb/host/xhci-dwc3.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/usb/host/xhci-dwc3.c b/drivers/usb/host/xhci-dwc3.c
> index e3e0ceff43e..7b1311503fe 100644
> --- a/drivers/usb/host/xhci-dwc3.c
> +++ b/drivers/usb/host/xhci-dwc3.c
> @@ -208,6 +208,9 @@ 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));

Although this proposal was suggested in [1] and later clarified in
[2] I will summarize the discussion here.

This patch fix is not sufficient for all cases as the xhci-dwc3.c
driver will still be probed if dr_mode is OTG or HOST along with
other platform drivers if enabled in config.

The only current solution is not not enable CONFIG_USB_XHCI_DWC3
together with another platform driver config (e.g. CONFIG_USB_DWC3_GENERIC)
if snps,dwc3 should not be managed by xhci-dwc3.c.

[1] - https://lore.kernel.org/all/unf757pwgah5ylkcfdumtdo5zs2ny3nxct5u26t6up7aldqim2@mxhhtb53gw4x/
[2] - https://lore.kernel.org/all/a9c458f8-68e5-448b-9977-e7bf37b00d35@kernel.org/

-- 
cheers,
-roger