Re: [PATCH v8 12/29] phy: rockchip: usbdp: Support single-lane DP

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Unclocked PHY register access caused by returning 0 on unsupported mode in `rk_udphy_power_on`.
--

commit 835e45901918a9b24aa9d7ccd7b8538db264146b
Author: Zhang Yubing <yubing.zhang@rock-chips.com>

phy: rockchip: usbdp: Support single-lane DP

Implement support for using just a single DisplayPort line.

> diff --git a/drivers/phy/rockchip/phy-rockchip-usbdp.c b/drivers/phy/rockchip/phy-rockchip-usbdp.c
> --- a/drivers/phy/rockchip/phy-rockchip-usbdp.c
> +++ b/drivers/phy/rockchip/phy-rockchip-usbdp.c
[ ... ]
> @@ -1083,18 +1072,17 @@ static int rk_udphy_dp_phy_exit(struct phy *phy)
>  static int rk_udphy_dp_phy_power_on(struct phy *phy)
>  {
[ ... ]
>  	ret = rk_udphy_power_on(udphy, UDPHY_MODE_DP);
>  	if (ret)
>  		goto unlock;
>  
> -	rk_udphy_dplane_enable(udphy, dp_lanes);
> +	rk_udphy_dplane_enable(udphy, udphy->dp_lanes);
>  
>  	rk_udphy_dplane_select(udphy);

[Severity: High]
This is a pre-existing issue, but I noticed a potential problem in how
we handle the return value of rk_udphy_power_on() here.

If the DP controller powers on the DP PHY when DP mode is not currently
enabled, such as before Type-C negotiation completes or when forced by
userspace bypassing HPD checks, rk_udphy_power_on() returns 0 for
unsupported modes.

Because the return value is 0, execution proceeds to rk_udphy_dplane_enable()
and rk_udphy_dplane_select(). Can this cause a kernel crash or SError
resulting from an MMIO access to unclocked UDPHY_PMA registers?

Should rk_udphy_power_on() return an error code like -EOPNOTSUPP instead of
0 when the mode is not supported, so the check here can properly abort?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260626-rockchip-usbdp-cleanup-v8-0-47f682987895@collabora.com?part=12

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