Re: [PATCH v4 07/16] phy: rockchip: usbdp: Support single-lane DP

[Sebastian Reichel <sebastian.reichel@collabora.com>]

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Hi,

On Wed, May 06, 2026 at 04:53:07PM +0200, Neil Armstrong wrote:
> > @@ -537,6 +538,13 @@ static void rk_udphy_usb_bvalid_enable(struct rk_udphy *udphy, u8 enable)
> >    * <0 1>                  dpln0         dpln1       usbrx         usbtx
> >    * <2 3>                  usbrx         usbtx       dpln0         dpln1
> >    * ---------------------------------------------------------------------------
> > + * if 1 lane for dp function, 2 lane for usb function, define rockchip,dp-lane-mux = <x>;
> > + * sample as follow:
> > + * ---------------------------------------------------------------------------
> > + *                        B11-B10       A2-A3       A11-A10       B2-B3
> > + * rockchip,dp-lane-mux   ln0(tx/rx)    ln1(tx)     ln2(tx/rx)    ln3(tx)
> > + * <0>                    dpln0         \           usbrx         usbtx
> > + * ---------------------------------------------------------------------------
> >    */
> >   static void rk_udphy_dplane_select(struct rk_udphy *udphy)
> > @@ -544,18 +552,18 @@ static void rk_udphy_dplane_select(struct rk_udphy *udphy)
> >   	const struct rk_udphy_cfg *cfg = udphy->cfgs;
> >   	u32 value = 0;
> > -	switch (udphy->mode) {
> > -	case UDPHY_MODE_DP:
> > -		value |= 2 << udphy->dp_lane_sel[2] * 2;
> > +	switch (udphy->dp_lanes) {
> > +	case 4:
> >   		value |= 3 << udphy->dp_lane_sel[3] * 2;
> > +		value |= 2 << udphy->dp_lane_sel[2] * 2;
> >   		fallthrough;
> > -	case UDPHY_MODE_DP_USB:
> > -		value |= 0 << udphy->dp_lane_sel[0] * 2;
> > +	case 2:
> >   		value |= 1 << udphy->dp_lane_sel[1] * 2;
> > -		break;
> > +		fallthrough;
> > -	case UDPHY_MODE_USB:
> > +	case 1:
> > +		value |= 0 << udphy->dp_lane_sel[0] * 2;
> 
> What's the point of keeping this no-op calculation ?

This function is cleaned up in a later patch to no longer have the
switch/case at all ("Cleanup DP lane selection function"). I kept
the no-op calculation here, since it IMHO makes it easier to understand
the cleanup patch and will be optimized away by the compiler anyways.

(I will send out a new patch series in a jiffy)

Greetings,

-- Sebastian

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