linux-kernel - Re: [PATCH v3 2/2] interconnect: qcom: Add OSM L3 interconnect provider support

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Message-ID: <CAE=gft6Dr_=zQ1h93qdxzi-GsZv3caddyOGaGQpSi+8BmBSO+Q@mail.gmail.com>
Date:   Tue, 7 Jan 2020 11:14:58 -0800
From:   Evan Green <evgreen@...omium.org>
To:     Sibi Sankar <sibis@...eaurora.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Georgi Djakov <georgi.djakov@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <agross@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        David Dai <daidavid1@...eaurora.org>,
        Saravana Kannan <saravanak@...gle.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        linux-kernel-owner@...r.kernel.org
Subject: Re: [PATCH v3 2/2] interconnect: qcom: Add OSM L3 interconnect
 provider support

On Mon, Dec 16, 2019 at 10:30 AM Sibi Sankar <sibis@...eaurora.org> wrote:
>
> Hey Evan,
>
> On 12/7/19 12:46 AM, Evan Green wrote:
> > On Wed, Nov 27, 2019 at 12:42 AM Sibi Sankar <sibis@...eaurora.org> wrote:
> >>
> >> Hey Evan/Georgi,
> >>
> >> https://git.linaro.org/people/georgi.djakov/linux.git/commit/?h=icc-dev&id=9197da7d06e88666d1588e3c21a743e60381264d
> >>
> >> With the "Redefine interconnect provider
> >> DT nodes for SDM845" series, wouldn't it
> >> make more sense to define the OSM_L3 icc
> >> nodes in the sdm845.c icc driver and have
> >> the common helpers in osm_l3 driver? Though
> >> we don't plan on linking the OSM L3 nodes
> >> to the other nodes on SDM845/SC7180, we
> >> might have GPU needing to be linked to the
> >> OSM L3 nodes on future SoCs. Let me know
> >> how you want this done.
> >>
> >> Anyway I'll re-spin the series once the
> >> SDM845 icc re-work gets re-posted.
> >
> > I don't have a clear picture of the proposal. You'd put the couple of
> > extra defines in sdm845.c for the new nodes. But then you'd need to do
> > something in icc_set() of sdm845. Is that when you'd call out to the
> > osm_l3 driver?
>
> with sdm845 icc rework "https://patchwork.kernel.org/cover/11293399/"
> osm l3 icc provider needs to know the total number of rsc icc nodes,
> i.e I can define the total number of rsc nodes and continue using the
> same design as v3 since on sdm845/sc7180 gpu is not cache coherent.
>
> or have the osm l3 table population logic and osm icc_set as helpers
> and have it called from the sdm845/sc7180 icc driver so that we would
> be able to link osm_l3 with rsc nodes on future qcom SoCs.

I see, so if we use the same design as v3, then the number of nodes is
established at compile-time, and ends up being specific to sdm845. I'm
fine with either approach, maybe leaning towards the hardcoded
#defines you have now, and waiting to do the refactoring until you
actually have two SoCs that can use this.
-Evan