linux-kernel - Re: [PATCH v3 1/3] drm/msm/a6xx: Add support for an interconnect path

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Date:   Fri, 18 Jan 2019 14:16:32 -0500
From:   Rob Clark <robdclark@...il.com>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Jordan Crouse <jcrouse@...eaurora.org>,
        Georgi Djakov <georgi.djakov@...aro.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Stephen Boyd <swboyd@...omium.org>,
        Kees Cook <keescook@...omium.org>,
        Sharat Masetty <smasetty@...eaurora.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andy Gross <andy.gross@...aro.org>,
        David Airlie <airlied@...ux.ie>,
        Johan Hovold <johan@...nel.org>,
        Colin Ian King <colin.king@...onical.com>,
        Evan Green <evgreen@...omium.org>,
        Sean Paul <seanpaul@...omium.org>
Subject: Re: [PATCH v3 1/3] drm/msm/a6xx: Add support for an interconnect path

On Fri, Jan 18, 2019 at 1:06 PM Doug Anderson <dianders@...omium.org> wrote:
>
> Hi,
>
> On Thu, Dec 20, 2018 at 9:30 AM Jordan Crouse <jcrouse@...eaurora.org> wrote:
> >
> > Try to get the interconnect path for the GPU and vote for the maximum
> > bandwidth to support all frequencies. This is needed for performance.
> > Later we will want to scale the bandwidth based on the frequency to
> > also optimize for power but that will require some device tree
> > infrastructure that does not yet exist.
> >
> > v5: Remove hardcoded interconnect name and just use the default
>
> nit: ${SUBJECT} says v3, but this is v5.
>
> I'll put in my usual plug for considering "patman" to help post
> patches.  Even though it lives in the u-boot git repo it's still a gem
> for kernel work.
> <http://git.denx.de/?p=u-boot.git;a=blob;f=tools/patman/README>
>
>
> > @@ -85,6 +89,12 @@ static void __a6xx_gmu_set_freq(struct a6xx_gmu *gmu, int index)
> >                 dev_err(gmu->dev, "GMU set GPU frequency error: %d\n", ret);
> >
> >         gmu->freq = gmu->gpu_freqs[index];
> > +
> > +       /*
> > +        * Eventually we will want to scale the path vote with the frequency but
> > +        * for now leave it at max so that the performance is nominal.
> > +        */
> > +       icc_set(gpu->icc_path, 0, MBps_to_icc(7216));
>
> You'll need to change icc_set() here to icc_set_bw() to match v13, AKA:
>
> - https://patchwork.kernel.org/patch/10766335/
> - https://lkml.kernel.org/r/20190116161103.6937-2-georgi.djakov@linaro.org
>
>
> > @@ -695,6 +707,9 @@ int a6xx_gmu_resume(struct a6xx_gpu *a6xx_gpu)
> >         if (ret)
> >                 goto out;
> >
> > +       /* Set the bus quota to a reasonable value for boot */
> > +       icc_set(gpu->icc_path, 0, MBps_to_icc(3072));
>
> This will also need to change to icc_set_bw()
>
>
> > @@ -781,6 +798,9 @@ int a6xx_gmu_stop(struct a6xx_gpu *a6xx_gpu)
> >         /* Tell RPMh to power off the GPU */
> >         a6xx_rpmh_stop(gmu);
> >
> > +       /* Remove the bus vote */
> > +       icc_set(gpu->icc_path, 0, 0);
>
> This will also need to change to icc_set_bw()
>
>
> I have the same questions for this series that I had in response to
> the email ("[v5 2/3] drm/msm/dpu: Integrate interconnect API in MDSS")
> <https://lkml.kernel.org/r/CAD=FV=XUeMTGH+CDwGs3PfK4igdQrCbwucw7_2ViBc4i7grvxg@mail.gmail.com>
>
>
> Copy / pasting here (with minor name changes) so folks don't have to
> follow links / search email.
>
> ==
>
> I'm curious what the plan is for landing this series.   Rob / Gerogi:
> do you have any preference?  Options I'd imagine:
>
> A) Wait until interconnect lands (in 5.1?) and land this through
> msm-next in the version after (5.2?)
>
> B) Georgi provides an immutable branch for interconnect when his lands
> (assuming he's landing via pull request) and that gets pulled into the
> the relevant drm tree.
>
> C) Rob Acks this series and indicates that it should go in through
> Gerogi's tree (probably only works if Georgi plans to send a pull
> request).  If we're going this route then (IIUC) we'd want to land
> this in Gerogi's tree sooner rather than later so it can get some bake
> time?  NOTE: as per my prior reply, I believe Rob has already Acked
> this patch.
>

I'm ok to ack and have it land via Georgi's tree, if Georgi wants to
do that.  Or otherwise, I could maybe coordinate w/ airlied to send a
2nd late msm-next pr including the gpu and display interconnect
patches.

BR,
-R

>
> Does anyone have a preference?  It's be nice if whoever is planning to
> land this could indicate whether they'd prefer Jordan send a new
> version to handle the API change or if the relevant maintainer can
> just do the fixup when the patch lands.
>
>
> Thanks!
>
>
> -Doug