linux-kernel - Re: [PATCH v6 03/18] clk: qcom: gcc-ipq806x: add PXO

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Message-ID: <62570e48.1c69fb81.49fb8.143b@mx.google.com>
Date:   Wed, 13 Apr 2022 19:54:15 +0200
From:   Ansuel Smith <ansuelsmth@...il.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Stephen Boyd <sboyd@...nel.org>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 03/18] clk: qcom: gcc-ipq806x: add PXO_SRC in clk table

On Wed, Apr 13, 2022 at 08:32:21PM +0300, Dmitry Baryshkov wrote:
> On Wed, 13 Apr 2022 at 20:00, Ansuel Smith <ansuelsmth@...il.com> wrote:
> >
> > On Thu, Mar 24, 2022 at 06:22:29PM -0700, Stephen Boyd wrote:
> > > Quoting Ansuel Smith (2022-03-24 18:13:49)
> > > > On Thu, Mar 24, 2022 at 06:10:35PM -0700, Stephen Boyd wrote:
> > > > > Quoting Ansuel Smith (2022-03-21 16:15:33)
> > > > > > PXO_SRC is currently defined in the gcc include and referenced in the
> > > > > > ipq8064 DTSI. Correctly provide a clk after gcc probe to fix kernel
> > > > > > panic if a driver starts to actually use it.
> > > > > >
> > > > > > Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
> > > > > > ---
> > > > >
> > > > > What is this patch about? clk providers shouldn't be calling clk_get().
> > > > >
> > > >
> > > > If pxo is passed as a clock in dts and defined as a fixed clock, what
> > > > should be used?
> > >
> > > clk_parent_data
> >
> > Sorry but I'm not following you. No idea if you missed the cover letter
> > where i describe the problem with PXO_SRC.
> >
> > The problem here is that
> > - In DTS we have node that reference <&gcc PXO_SRC>
> > But
> > - gcc driver NEVER defined PXO_SRC
> > As
> > - PXO_SRC is actually pxo_board that should be defined as a fixed-clock
> >   in dts or is defined using qcom_cc_register_board_clk.
> >
> > So in theory we should just put in PXO_SRC the clk hw of the
> > fixed-clock. That is why I'm using clk_get(). I can use __clk_lookup()
> > as an alternative but I really can't find a way to get the clock defined
> > from DTS or qcom_cc_register_board_clk.
> >
> > (I have the same exact problem with the cpu qsb clock where is defined
> > using fixed-clock API but can also defined directly in DTS and I have to
> > use clk_get())
> >
> > I'm totally missing something so I would love some hint on how to solve
> > this.
> 
> When we were doing such conversion for other  platforms, we pointed
> clock consumers to the board clocks directly. There is no need to go
> through the gcc to fetch pxo.
> Instead you can use a <&pxo_board> in the dts directly. Typically the
> sequence is the following:
> - Minor cleanup of the clock-controller driver
> (ARRAY_SIZE(parent_data), removal of unused clock sources, unused enum
> entries, etc)
> - update drivers to use both .name and  .fw_name in replacement of
> parent_names. Use parent_hws where possible.
> - update dtsi to reference clocks using clocks/clock-names properties.
> Pass board/rpmh/rpm clocks directly to their consumers without
> bandaids in the gcc driver.
> - (optionally) after several major releases drop parent_data.name
> completely. I think we mostly skipped this, since it provides no gain.
> 
> This way you don't have to play around clk_get to return PXO_SRC from
> gcc clock-controller.
> 
> -- 
> With best wishes
> Dmitry

Thanks for the list of steps to do this kind of cleanup.
>From what I'm reading this series is ""stuck"" in the sense that I first
have to fix the wrong PXO_SRC reference and then I can continue the
conversion work. A bit sad considering most of the time DTS proposal got
ignored :(

-- 
	Ansuel