Re: [PATCH 05/10] dt-bindings: interconnect: Add sm8350, sc8280xp and generic OSM L3 compatibles

Bjorn Andersson
2022-11-03T15:47:02Z

On Thu, Nov 03, 2022 at 08:25:17AM -0400, Krzysztof Kozlowski wrote:
> On 02/11/2022 23:44, Bjorn Andersson wrote:
> > On Fri, Oct 28, 2022 at 06:12:29PM -0400, Krzysztof Kozlowski wrote:
> >> On 27/10/2022 23:41, Bjorn Andersson wrote:
> >>> Add EPSS L3 compatibles for sm8350 and sc8280xp, but while at it also
> >>> introduce generic compatible for both qcom,osm-l3 and qcom,epss-l3.
> >>>
> >>> Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
> >>> ---
> >>> .../bindings/interconnect/qcom,osm-l3.yaml | 22 +++++++++++++------
> >>> 1 file changed, 15 insertions(+), 7 deletions(-)
> >>>
> >>> diff --git a/Documentation/devicetree/bindings/interconnect/qcom,osm-l3.yaml b/Documentation/devicetree/bindings/interconnect/qcom,osm-l3.yaml
> >>> index bf538c0c5a81..ae0995341a78 100644
> >>> --- a/Documentation/devicetree/bindings/interconnect/qcom,osm-l3.yaml
> >>> +++ b/Documentation/devicetree/bindings/interconnect/qcom,osm-l3.yaml
> >>> @@ -16,13 +16,21 @@ description:
> >>>
> >>> properties:
> >>> compatible:
> >>> - enum:
> >>> - - qcom,sc7180-osm-l3
> >>> - - qcom,sc7280-epss-l3
> >>> - - qcom,sc8180x-osm-l3
> >>> - - qcom,sdm845-osm-l3
> >>> - - qcom,sm8150-osm-l3
> >>> - - qcom,sm8250-epss-l3
> >>> + oneOf:
> >>> + items:
> >>
> >> oneOf expects a list, so this should be " - items"
> >>
> >
> > Ahh, thanks. Must have missed running the dt_binding_check on this one.
> >
> >>> + - enum:
> >>> + - qcom,sc7180-osm-l3
> >>> + - qcom,sc8180x-osm-l3
> >>> + - qcom,sdm845-osm-l3
> >>> + - qcom,sm8150-osm-l3
> >>> + - const: qcom,osm-l3
> >>
> >> The concept is good, but are you sure all SoCs will be compatible with
> >> generic osm-l3?
> >
> > Per the current implementation yes, worst case if one or more of them isn't the
> > more specific compatible can be used to alter the behavior of that platform.
> >
> >> Why not using dedicated compatible of one soc, e.g. the
> >> oldest here? We already did like that for BWMON, DMA and few others.
> >>
> >
> > Because if we say compatible = "qcom,sc8180x-osm-l3", "qcom,sdm845-osm-l3" and
> > there is a quirk needed for "qcom,sdm845-osm-l3" we're forced to add a "special
> > case" every other *-osm-l3 in the driver.
> >
> > This way we can have a generic implementation for the qcom,osm-l3 and if we
> > realize that we need to quirk something for the oldest platform, we can do so
> > without affecting the others.
>
> True. This also means we do not really know which one is the generic
> implementation :)
>

There currently is an implementation without platform specific quirks, I
call that the generic implementation and suggest that we refer to that
using "qcom,osm-l3".

If we instead were to use sdm845 as the generic compatible, and there
turns out to be a need for a quirk for this platform, you:

1) no longer have a generic implementation, but 4 platform-specific
implementations

2) have 3 platforms claiming to be compatible with the quirked (now
specialized) implementation, which they clearly aren't anymore

Therefor I favor using generic names for generic compatibles.

Regards,
Bjorn