Re: [PATCH v8 09/10] dt-bindings: interconnect: Add interconnect-tags bindings

[Sibi Sankar]

On 5/21/20 12:43 AM, Saravana Kannan wrote:
> On Wed, May 20, 2020 at 11:51 AM Sibi Sankar <sibis@xxxxxxxxxxxxxx> wrote:
> > On 2020-05-20 01:27, Saravana Kannan wrote:
> > > On Tue, May 19, 2020 at 11:58 AM Rob Herring <robh@xxxxxxxxxx> wrote:
> > > > On Tue, May 12, 2020 at 03:53:26PM +0300, Georgi Djakov wrote:
> > > > > From: Sibi Sankar <sibis@xxxxxxxxxxxxxx>
> > > > >
> > > > > Add interconnect-tags bindings to enable passing of optional
> > > > > tag information to the interconnect framework.
> > > > >
> > > > > Signed-off-by: Sibi Sankar <sibis@xxxxxxxxxxxxxx>
> > > > > Signed-off-by: Georgi Djakov <georgi.djakov@xxxxxxxxxx>
> > > > > ---
> > > > > v8:
> > > > > * New patch, picked from here:
> > > > >    https://lore.kernel.org/r/20200504202243.5476-10-sibis@xxxxxxxxxxxxxx
> > > > >
> > > > >   .../devicetree/bindings/interconnect/interconnect.txt        | 5 +++++
> > > > >   1 file changed, 5 insertions(+)
> > > > >
> > > > > diff --git a/Documentation/devicetree/bindings/interconnect/interconnect.txt b/Documentation/devicetree/bindings/interconnect/interconnect.txt
> > > > > index 6f5d23a605b7..c1a226a934e5 100644
> > > > > --- a/Documentation/devicetree/bindings/interconnect/interconnect.txt
> > > > > +++ b/Documentation/devicetree/bindings/interconnect/interconnect.txt
> > > > > @@ -55,6 +55,11 @@ interconnect-names : List of interconnect path name strings sorted in the same
> > > > >                         * dma-mem: Path from the device to the main memory of
> > > > >                                    the system
> > > > >
> > > > > +interconnect-tags : List of interconnect path tags sorted in the same order as the
> > > > > +                 interconnects property. Consumers can append a specific tag to
> > > > > +                 the path and pass this information to the interconnect framework
> > > > > +                 to do aggregation based on the attached tag.
> > > >
> > > > Why isn't this information in the 'interconnect' arg cells?
> > > >
> > > > We have 'interconnect-names' because strings don't mix with cells. An
> > > > expanding list of 'interconnect-.*' is not a good pattern IMO.
> >
> > Rob,
> > Currently the interconnect paths
> > assume a default tag and only few
> > icc paths require tags that differ
> > from the default ones. Encoding the
> > tags in the interconnect arg cells
> > would force all paths to specify
> > the tags. I guess that's okay.
>
> I think that's the right thing. Those cells are meant to be "args" to
> the provider.

diff --git a/arch/arm64/boot/dts/qcom/sc7180.dtsi 
b/arch/arm64/boot/dts/qcom/sc7180.dtsi

index ea4764f06a901..b34f024d4ab63 100644

--- a/arch/arm64/boot/dts/qcom/sc7180.dtsi

+++ b/arch/arm64/boot/dts/qcom/sc7180.dtsi

@@ -132,9 +132,8 @@ &LITTLE_CPU_SLEEP_1

                        capacity-dmips-mhz = <1024>;

                        dynamic-power-coefficient = <100>;

                        operating-points-v2 = <&cpu0_opp_table>;

-                       interconnects = <&gem_noc MASTER_APPSS_PROC 
&mc_virt SLAVE_EBI1>,

+                       interconnects = <&gem_noc MASTER_APPSS_PROC 3 
&mc_virt SLAVE_EBI1 3>,

                                        <&osm_l3 MASTER_OSM_L3_APPS 
&osm_l3 SLAVE_OSM_L3>;

                        next-level-cache = <&L2_0>;

                        #cooling-cells = <2>;

                        qcom,freq-domain = <&cpufreq_hw 0>;



....

                mc_virt: interconnect@1638000 {

                        compatible = "qcom,sc7180-mc-virt";

                        reg = <0 0x01638000 0 0x1000>;

-                       #interconnect-cells = <1>;

+                       #interconnect-cells = <2>;

                        qcom,bcm-voters = <&apps_bcm_voter>;

                };

....



@@ -2216,14 +2208,14 @@ system-cache-controller@9200000 {

                gem_noc: interconnect@9680000 {

                        compatible = "qcom,sc7180-gem-noc";

                        reg = <0 0x09680000 0 0x3e200>;

-                       #interconnect-cells = <1>;

+                       #interconnect-cells = <2>;

                        qcom,bcm-voters = <&apps_bcm_voter>;

                };

....



diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c

index 294e9c58565bb..6a7a785bd90b9 100644

--- a/drivers/interconnect/core.c

+++ b/drivers/interconnect/core.c

@@ -340,7 +340,7 @@ static struct icc_node 
*of_icc_get_from_provider(struct of_phandle_args *spec)

        struct icc_node *node = ERR_PTR(-EPROBE_DEFER);

        struct icc_provider *provider;



-       if (!spec || spec->args_count != 1)

+       if (!spec || spec->args_count < 1)

                return ERR_PTR(-EINVAL);



        mutex_lock(&icc_lock);

@@ -469,6 +469,9 @@ struct icc_path *of_icc_get_by_index(struct device 
*dev, int idx)

                return ERR_PTR(-ENOMEM);

        }



+       if (src_args.args_count == 2)

+               icc_set_tag(path, src_args.args[1]);

diff: https://paste.ubuntu.com/p/sRRYhxQjsV/

Saravana/Georgi,
A few concerns here, I feel tag info as the second arg to the provider
may not be true for all socs. Does introducing soc specific of_icc_get
functions make sense?

> > > Also, is there an example for interconnect-tags that I missed? Is it a
> > > list of strings, numbers, etc?
> >
> > Saravana,
> > https://patchwork.kernel.org/patch/11527589/
> > ^^ is an example of interconnect-tag useage.
>
> If we actually merge interconnect-tags, I think the doc should be
> updated. Instead of having to grep around.
>
> -Saravana

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