Message-ID: <CAA8EJpr47F6x+GhV1z_uLWmGFKCdYCoohvi_A83SBynKGf=qkA@mail.gmail.com>
Date:   Tue, 7 Dec 2021 05:00:20 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        Rob Clark <robdclark@...il.com>
Subject: Re: [PATCH] of: property: do not create clocks device link for clock controllers

Hi Saravana,

On Tue, 30 Nov 2021 at 03:24, Dmitry Baryshkov
<dmitry.baryshkov@...aro.org> wrote:
>
> On Tue, 30 Nov 2021 at 02:53, Saravana Kannan <saravanak@...gle.com> wrote:
> >
> > On Mon, Nov 29, 2021 at 3:48 PM Saravana Kannan <saravanak@...gle.com> wrote:
> > >
> > > On Thu, Nov 25, 2021 at 10:36 AM Dmitry Baryshkov
> > > <dmitry.baryshkov@...aro.org> wrote:
> > > >
> > > > Do not create device link for clock controllers.
> > >
> > > Nak.
> > >
> > > > Some of the clocks
> > > > provided to the device via OF can be the clocks that are just parents to
> > > > the clocks provided by this clock controller. Clock subsystem already
> > > > has support for handling missing clock parents correctly (clock
> > > > orphans). Later when the parent clock is registered, clocks get
> > > > populated properly.
> > > >
> > > > An example of the system where this matters is the SDM8450 MTP board
> > > > (see arch/arm64/boot/dts/qcom/sdm845-mtp.dts). Here the dispcc uses
> > > > clocks provided by dsi0_phy and dsi1_phy device tree nodes. However the
> > > > dispcc itself provides clocks to both PHYs, to the PHY parent device,
> > > > etc. With just dsi0_phy in place devlink is able to break the
> > > > dependency,
> > >
> > > Right, because I wrote code to make sure we handle these clock
> > > controller cases properly. If that logic isn't smart enough, let's fix
> > > that.
>
> As I said, devlink was delaying dispcc probing ,waiting for the second
> DSI PHY clock provider.
> Thus came my proposal to let clock orphans handle the case (which it
> does perfectly).
>
> > >
> > > > but with two PHYs, dispcc doesn't get probed at all, thus
> > > > breaking display support.
> > >
> > > Then let's find out why and fix this instead of hiding some
> > > dependencies from fw_devlink. You could be breaking other cases/boards
> > > with this change you are making.
> >
> > Btw, forgot to mention. I'll look into this one and try to find the
> > reason why it wasn't handled automatically. And then come up with a
> > fix.
> >
> > If you want to find out why fw_devlink didn't notice the cycle
> > correctly for the case of 2 PHYs vs 1 PHY, I'd appreciate that too.
> >
> > Btw, same comment for remote-endpoint. I'll look into what's going on
> > in that case. Btw, I'm assuming all the code and DT you are testing
> > this on is already upstream. Can you please confirm that?
>
> All the code and basic DT is upstreamed. The DT part I
> referenced/posted was written for the custom extender for the
> qrb5165-rb5 board that I use here to test MSM DRM driver, but the
> result DT should be more or less the same as smd845-mtp.

So, is there a way we can assist you in debugging these issues? I
still can not get dual DSI setup to work without this patch (or
without disabling fw_devlink).

>
> >
> > -Saravana
> >
> > >
> > > -Saravana
> > >
> > > > Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
> > > > Cc: Stephen Boyd <swboyd@...omium.org>
> > > > Cc: Saravana Kannan <saravanak@...gle.com>
> > > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> > > > ---
> > > >  drivers/of/property.c | 16 +++++++++++++++-
> > > >  1 file changed, 15 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/of/property.c b/drivers/of/property.c
> > > > index a3483484a5a2..f7229e4030e3 100644
> > > > --- a/drivers/of/property.c
> > > > +++ b/drivers/of/property.c
> > > > @@ -1264,7 +1264,6 @@ struct supplier_bindings {
> > > >         bool node_not_dev;
> > > >  };
> > > >
> > > > -DEFINE_SIMPLE_PROP(clocks, "clocks", "#clock-cells")
> > > >  DEFINE_SIMPLE_PROP(interconnects, "interconnects", "#interconnect-cells")
> > > >  DEFINE_SIMPLE_PROP(iommus, "iommus", "#iommu-cells")
> > > >  DEFINE_SIMPLE_PROP(mboxes, "mboxes", "#mbox-cells")
> > > > @@ -1294,6 +1293,21 @@ DEFINE_SIMPLE_PROP(backlight, "backlight", NULL)
> > > >  DEFINE_SUFFIX_PROP(regulators, "-supply", NULL)
> > > >  DEFINE_SUFFIX_PROP(gpio, "-gpio", "#gpio-cells")
> > > >
> > > > +static struct device_node *parse_clocks(struct device_node *np,
> > > > +                                       const char *prop_name, int index)
> > > > +{
> > > > +       /*
> > > > +        * Do not create clock-related device links for clocks controllers,
> > > > +        * clock orphans will handle missing clock parents automatically.
> > > > +        */
> > > > +       if (!strcmp(prop_name, "clocks") &&
> > > > +           of_find_property(np, "#clock-cells", NULL))
> > > > +               return NULL;
> > > > +
> > > > +       return parse_prop_cells(np, prop_name, index, "clocks",
> > > > +                                      "#clock-cells");
> > > > +}
> > > > +
> > > >  static struct device_node *parse_gpios(struct device_node *np,
> > > >                                        const char *prop_name, int index)
> > > >  {
> > > > --
> > > > 2.33.0
> > > >
>
>
>
> --
> With best wishes
> Dmitry



-- 
With best wishes
Dmitry

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