Re: [PATCH 02/14] dt-bindings: phy: qcom,qmp-usb3-dp: fix sc8280xp bindings

[Dmitry Baryshkov]

On 14/11/2022 17:18, Johan Hovold wrote:
> On Mon, Nov 14, 2022 at 03:07:41PM +0100, Krzysztof Kozlowski wrote:
> > On 14/11/2022 14:27, Johan Hovold wrote:
> > > On Fri, Nov 11, 2022 at 04:17:29PM +0100, Krzysztof Kozlowski wrote:
> > > > On 11/11/2022 10:24, Johan Hovold wrote:
> > > > > The current QMP USB3-DP PHY bindings are based on the original MSM8996
> > > > > binding which provided multiple PHYs per IP block and these in turn were
> > > > > described by child nodes.
>
> > > > > +  "#clock-cells":
> > > > > +    const: 1
> > > > > +
> > > > > +  clock-output-names:
> > > > > +    items:
> > > > > +      - const: usb3_pipe
> > > > > +      - const: dp_link
> > > > > +      - const: dp_vco_div
> > > >
> > > > Why defining here fixed names? The purpose of this field is to actually
> > > > allow customizing these - at least in most cases. If these have to be
> > > > fixed, then driver should just instantiate these clocks with such names,
> > > > right?
> > >
> > > I'm only using these names as documentation of the indexes. The driver
> >
> > What do you mean by documentation of indexes? You require these specific
> > entries and do not allow anything else.
>
> I'm using this property as documentation of the valid indexes that can
> be used when referring to clocks provided by this device.
>
> There are currently three and the mapping is described by the
> 'clock-output-names' property.
>   
> > > doesn't use these names, but that's a Linux-specific implementation
> > > detail.
> > >
> > > I noticed that several bindings leave the clock indexes unspecified, or
> > > have header files defining some or all of them. I first added a QMP
> > > header but that seemed like overkill, especially if we'd end up with
> > > one header per SoC (cf. the GCC headers) due to (known and potential)
> > > platform differences.
> >
> > Headers for the names? I do not recall such but that does not seem right.
>
> Headers for the indexes.
>
> > > On the other hand reproducing this list in each node is admittedly a bit
> > > redundant.
> > >
> > > Shall I add back a shared header for all PHYs handled by this driver
> > > (another implementation detail) even if this could eventually lead to
> > > describing clocks not supported by a particular SoC (so such constraints
> > > would still need to be described by the binding somehow):
> > >
> > > 	/* QMP clocks */
> > > 	#define QMP_USB3_PIPE_CLK	0
> > > 	#define QMP_DP_LINK_CLK		1
> > > 	#define QMP_DP_VCO_DIV_CLK	2

Maybe QMP_COMBO_USB3_PIPE_CLK, QMP_COMBO_DP_LINK_CLK, 
QMP_COMBO_DP_VCO_DIV_CLK?

I'll then extend this header with QMP_UFS_RX_SYMBOL_0_CLK 
QMP_UFS_RX_SYMBOL_1_CLK and QMP_UFS_TX_SYMBOL_0_CLK.

> > What are these about? To remind - we talk about names of clocks this
> > device creates. The output names. Whatever IDs you have are not related
> > to the names.
>
> As I mentioned above, this is not about the names that Linux gives to
> its representation of these clocks. Its just about defining the valid
> indexes in the binding.
>
> If you think that that using 'clock-output-names' for this is a bit too
> unconventional, I can add back the header with defines like the above
> instead.
>
> Note that the clock schema has:
>
>    clock-output-names:
>      description: |
>        Recommended to be a list of strings of clock output signal
>        names indexed by the first cell in the clock specifier.
>        However, the meaning of clock-output-names is domain
>        specific to the clock provider, ...
>
> Johan

--
With best wishes
Dmitry