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

[Dmitry Baryshkov]

On 14/11/2022 19:42, Johan Hovold wrote:
> On Mon, Nov 14, 2022 at 07:14:48PM +0300, Dmitry Baryshkov wrote:
> > On 14/11/2022 18:38, Johan Hovold wrote:
> > > On Mon, Nov 14, 2022 at 06:19:25PM +0300, Dmitry Baryshkov wrote:
> > > > 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:
> > >
> > > > > > > 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.
> > >
> > > > > > > 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?
> > >
> > > "COMBO" is just the name of the Linux driver and does not belong in the
> > > binding.
> >
> > We do not have any standard (iow, coming from the docs) name, so we can
> > invent it on our own.
>
> I still think the naming should reflect the hardware and not the Linux
> implementation if this is going into the binding.

Well, I always viewed docs as

> And the USB4_USB3_DP defines are going to be a superset of USB3_DP (as
> far we know know).
>
> > > > 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.
> > >
> > > Yeah, I had those in mind when creating the header and using a generic
> > > QMP prefix (even if I didn't end up using the header in v1).
> > >
> > > This could just be mapping of (arbitrary) QMP indexes to clocks and we
> > > use it for USB3, DP, UFS and later also USB4.
> > >
> > > This will however mean that the indexes are not necessarily zero-based
> > > and consecutive for a specific SoC and PHY. But that's perhaps a
> > > non-issue (cf. the PHY_TYPE defines).
> >
> > Ugh. Please, no. We have symbol clocks for UFS PHY, USB+DP clocks for
> > USB+DP PHY, but let's not go for the unified clocks index definition.
>
> Yeah, this is the kind of issues I wanted to avoid by not using a per
> SoC header for three clocks which will almost always use the same
> indexes.
>
> Because how can you be sure that your unified per-PHY type defines will
> never have to be amended? Or some index left out?
>
> The only way then is to have per-SoC defines which is a pain to
> maintain (just consider that driver mapping table when some odd SoC
> shows up).

My vote is definitely against a per-SoC defines.

> Johan

--
With best wishes
Dmitry