Re: [PATCH v4 2/2] phy: qcom-mipi-csi2: Add a CSI2 MIPI DPHY driver

[Neil Armstrong]

On 3/18/26 14:17, Bryan O'Donoghue wrote:
> On 18/03/2026 10:15, Neil Armstrong wrote:
> > > +    /*
> > > +     * phy_configure_opts_mipi_dphy.lanes starts from zero to
> > > +     * the maximum number of enabled lanes.
> > > +     *
> > > +     * TODO: add support for bitmask of enabled lanes and polarities
> > > +     * of those lanes to the phy_configure_opts_mipi_dphy struct.
> > > +     * For now take the polarities as zero and the position as fixed
> > > +     * this is fine as no current upstream implementation maps otherwise.
> > > +     */
> >
> > This is wrong since you loose the lanes mapping defined in DT, which is still in CAMSS
> > but is a PHY property. The lanes layout is not a property of the CSI controller,
> > CSI controller only need to know the lanes count, and not the layout.
>
> Lane layout is a PHY concern but, the PHY API gives us phy_configure_opts_mipi_dphy which should be extended to provide layout and polarity. This would then be of benefit to more than just qcom/camss.

Why ? the only concern between a controller and a PHY is the lane count to calculate the bandwidth, the actual pin layout is certainly not a controller concern.

> Right now none of the CAMSS users for this driver depend on any other mapping and I propose a separate series to fix phy_configure_opts_mipi_dphy rather than introduce data-lanes to DPHY.

None of the upstream users of camss.

The problem is even larger, as you replied in [1], the csiphy is still exposed as a media element from the CAMSS driver, this means this driver is not complete,
it should be a media driver entirely with eventually an internal PHY aux driver, but this would be entirely implementation specific.

Either the PHY is standalone and the PHY consumer only calls phy_open/init/configure/power_on/power_off/exit, otherwise it's not a fully standaline PHY but a composite device like here.

I propose that you write a proper media driver for the qcom csiphy, which eventually spins a PHY driver as an aux device.

Neil

> ---
> bod