Date:   Thu, 31 May 2018 11:01:09 +0100
From:   M P <buserror@...il.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     michel.pollet@...renesas.com, linux-renesas-soc@...r.kernel.org,
        Simon Horman <horms@...ge.net.au>,
        Phil Edworthy <phil.edworthy@...esas.com>,
        buserror+upstream@...il.com,
        Michael Turquette <mturquette@...libre.com>, sboyd@...nel.org,
        robh+dt@...nel.org, mark.rutland@....com, geert+renesas@...der.be,
        linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 1/5] dt-bindings: Add the r9a06g032-sysctrl.h file

Hi Geert,

On Thu, 31 May 2018 at 10:32, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> Hi Michel,
>
> On Thu, May 31, 2018 at 11:11 AM, M P <buserror@...il.com> wrote:
> > On Fri, 25 May 2018 at 11:31, Geert Uytterhoeven <geert@...ux-m68k.org>
> > wrote:
> >> On Thu, May 24, 2018 at 11:28 AM, Michel Pollet
> >> <michel.pollet@...renesas.com> wrote:
> >> > This adds the constants necessary to use the renesas,r9a06g032-sysctrl
> > node.
>
> >> > @@ -0,0 +1,187 @@
> >> > +/* SPDX-License-Identifier: GPL-2.0 */
> >> > +/*
> >> > + * R9A06G032 sysctrl IDs
> >> > + *
> >> > + * Copyright (C) 2018 Renesas Electronics Europe Limited
> >> > + *
> >> > + * Michel Pollet <michel.pollet@...renesas.com>, <buserror@...il.com>
> >> > + * Derived from zx-reboot.c
> >> > + */
> >> > +
> >> > +#ifndef __DT_BINDINGS_R9A06G032_SYSCTRL_H__
> >> > +#define __DT_BINDINGS_R9A06G032_SYSCTRL_H__
> >> > +
> >> > +#define R9A06G032_CLKOUT                       0
> >> > +#define R9A06G032_CLK_PLL_USB                  1
> >> > +#define R9A06G032_CLK_48                       1 /* AKA CLK_PLL_USB */
> >> > +#define R9A06G032_CLKOUT_D10                   2
> >> > +#define R9A06G032_CLKOUT_D16                   3
> >> > +#define R9A06G032_MSEBIS_CLK                   3 /* AKA CLKOUT_D16 */
> >> > +#define R9A06G032_MSEBIM_CLK                   3 /* AKA CLKOUT_D16 */
> >> > +#define R9A06G032_CLKOUT_D160                  4
> >> > +#define R9A06G032_CLKOUT_D1OR2                 5
> >> > +#define R9A06G032_CLK_DDRPHY_PLLCLK            5 /* AKA CLKOUT_D1OR2 */
> >
> >> [...]
> >
> >> I have 3 comments:
> >
> >>    1. I had expected this list to match (both name- and order-wise)
> > Appendix
> >>       C ("Clock Tree Structure") in the RZ/N1[DSL] User’s Manual: System
> >>       Introduction, Multiplexing, Electrical and Mechanical Information.
> >>       That would make it easier to review.
> >
> > Well, that document was made a *long* time after the internal documentation
> > we used to generate the clock lists. There are a few things we had to do:
> >
> > * Renumber peripherals. We decided a long time ago that u-boot and linux
> > would stick to zero based peripherals, and not one based numbers. It's next
> > to impossible to keep mixing number based across software base, so we use
> > UART0 while the hardware manual mentions UART1 -- It *is* documented
> > extensively with out SDK, and makes life using linux a lot easier. It's
> > across all our SDK, u-boot, webapps readmes, howtos etc.
> >
> > * Rename some peripherals. Plenty of peripherals names made little sense
> > and had zero consistency, in fact, many names were different depending on
> > the place they were used! -- "flashnand"+"nand_flash"+"FNAND" etc,
> > "QUADSPI"+"QSPI" etc etc so we also re-normalized the names to match linux
> > conventions.
> >
> > * Other internal reasons I can't document here
> >
> > Also, the value here are made up anyway -- so I've decided to sort them to
> > make sure any clock that has a parent is numbered *after* the parent...
>
> Well, all of that combines makes it very hard for us to review the list.

I understand -- the previous format was a lot more readable, here I had to
work to make the table as small as I could, and quite a few bits of readability
were lost in the process. It's already a huge file.

I'm not sure if that would help, but here is the link to the old table
format I used
https://github.com/renesas-rz/rzn1_linux/blob/rzn1-stable/drivers/clk/rzn1/rzn1-clkctrl-tables.h

I had to throw that away to make up the new composite table that now contains
what was in the device tree file before. However the names are the same.

Perhaps I could change how I encode the register/bit pairs to use 8+8 bits to
make the hex constants more readable?

>
> >>    2. These definitions seems to be a mix of:
> >>         1. Internal core clocks,
> >>         2. Other core clocks,
> >>         3. Module clocks.
> >
> >>       The internal clocks do not need to be referenced from DT, so I would
> >>       not make them part of the DT bindings.
> >
> > Why? I'm told that "Bindings aren't for linux" -- why can't I imagine
> > 'something' needing them? Why would I decide NOT to include them,
> > as they are there? I 'factored' a few of them to the same number when
>
> Just general safety w.r.t. unchangeable DT definitions: anything that is
> not listed here cannot be declared wrong later.

Well, I need these #define *somewhere* as I use them in my driver. So what
do you want me to do?
+ Remove the header, move the constants into the driver?
+ Use hard coded numbers in the DT and remove the header entirely?
+ Duplicate the header, keep the full one with the driver, and only list
the CA7+UART0 one in the dt-binding and duplicate the ones I need as
I go along?

>
> > applicable.
>
> You're 100% sure they're the same?

Yes, the script logic hasn't changed in 2 years, and we've been using that
hierarchy extensively since.
Basically the logic is that if a clock doesn't have a gate and isn't a divisor
of some sort, it's factored with it's parent clock... it used to be
done with a DT
alias of the same name.

>
> > This is all done automatically BTW -- a script takes the original clocking
> > spreadsheet, and converts it into a table, correcting 'human input' as it
> > goes along.
>
> So the internal spreadsheet doesn't match the public documentation neither?

Nope, as usual, people who wrote the documentation went their own way at
some point, and didn't backport any changes they made.

> Gr{oetje,eeting}s,
>
>                         Geert

Cheers,
Michel

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