linux-kernel - Re: (subset) [PATCH v12 00/19] Support spread spectrum clocking for i.MX8M PLLs

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Message-ID: <CABGWkvq=pXhrzyCV2ABvQ3uwx4qKYL_G9280p5ECb8nsJ859yw@mail.gmail.com>
Date: Fri, 23 May 2025 17:19:03 +0200
From: Dario Binacchi <dario.binacchi@...rulasolutions.com>
To: Abel Vesa <abel.vesa@...aro.org>
Cc: linux-kernel@...r.kernel.org, Peng Fan <peng.fan@....com>, 
	Stephen Boyd <sboyd@...nel.org>, Shawn Guo <shawnguo@...nel.org>, 
	linux-amarula@...rulasolutions.com, Abel Vesa <abelvesa@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Fabio Estevam <festevam@...il.com>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Michael Turquette <mturquette@...libre.com>, 
	Pengutronix Kernel Team <kernel@...gutronix.de>, Rob Herring <robh@...nel.org>, 
	Sascha Hauer <s.hauer@...gutronix.de>, devicetree@...r.kernel.org, imx@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org, 
	Michael Nazzareno Trimarchi <michael@...rulasolutions.com>
Subject: Re: (subset) [PATCH v12 00/19] Support spread spectrum clocking for
 i.MX8M PLLs

Hello Abel,

On Mon, May 5, 2025 at 9:52 AM Abel Vesa <abel.vesa@...aro.org> wrote:
>
>
> On Thu, 24 Apr 2025 08:21:30 +0200, Dario Binacchi wrote:
> > This version keeps the version v9 patches that can be merged and
> > removes the patches that will need to be modified in case Peng's
> > PR https://github.com/devicetree-org/dt-schema/pull/154 is accepted.
> > The idea is to speed up the merging of the patches in the series
> > that have already been reviewed and are not dependent on the
> > introduction of the assigned-clocks-sscs property, and postpone
> > the patches for spread spectrum to a future series once it becomes
> > clear what needs to be done.
> >
> > [...]
>
> Applied, thanks!

I was surprised to see that the series has been removed from linux-next.

It’s been 8 months since the first version dated September 28, 2024.
The most critical phase was version 3 -
https://lore.kernel.org/all/20241106090549.3684963-1-dario.binacchi@amarulasolutions.com/
-
where two key issues emerged:

 1 The CCM design is flawed because "in the current design, CCM is
   taken as the producer of CLK_IMX8M_VIDEO_PLL, not the consumer."

 2 A driver for anatop needs to be implemented because "using clocks
   to replace fsl,ssc-clocks is possible under CCM mode, but you need
   to develop the fsl,imx8mm-anatop clock driver."

These development guidelines, agreed upon with Krzysztof and Peng,
enabled a coherent implementation of both the DT bindings and the
code. The following versions, from v4 to v8, were necessary to
review and refine those implementations, bringing us to January 2025.

At that point, Peng opened a separate pull request -
https://github.com/devicetree-org/dt-schema/pull/154 -
for the definition of general-purpose DT bindings for spread spectrum
handling, which ended up invalidating mine.

While waiting for his pull request to be accepted, I submitted version 9,
trying to at least get the patches for the anatop driver merged,
eventually reaching version 12.

This final version was merged, but then a few days ago it was dropped.

As it stands now:

- We still don’t have proper spread spectrum handling
- Peng’s pull request has been stalled since February 20
- We don’t have a driver for anatop
- The CCM design remains flawed
- Not even the first 4 patches of the series were merged — these were
  simply a replication for i.MX8MM and i.MX8MP of patch
  bedcf9d1dcf88 ("clk: imx: rename video\_pll1 to video\_pll"), which
  was already merged some time ago.

Could you please let me know if you're still interested in this series?
If so, could you suggest how to resolve the issues that led you to drop it?

Thanks and regards,
Dario

>
> [01/19] dt-bindings: clock: imx8mm: add VIDEO_PLL clocks
>         commit: 20e5d201b5d8f830e702d7d183f6b1b246b78d8a
> [02/19] clk: imx8mm: rename video_pll1 to video_pll
>         commit: 26a33196b5b68cf199b6c4283a254aa92d2aaf4b
> [03/19] dt-bindings: clock: imx8mp: add VIDEO_PLL clocks
>         commit: 2d50415e2457c6f6621c2faa3b01b11150fb9c67
> [04/19] clk: imx8mp: rename video_pll1 to video_pll
>         commit: 21bb969f608cefd8d847cf6eb50a193d9f1fbb87
> [05/19] dt-bindings: clock: imx8m-anatop: add oscillators and PLLs
>         commit: 2ba124053687c933031a6dc5b2e16ceaca250934
> [10/19] clk: imx: add hw API imx_anatop_get_clk_hw
>         commit: 17e3c1a272d97e49b4f3fbfe1f1b889e120d2be8
> [11/19] clk: imx: add support for i.MX8MM anatop clock driver
>         commit: 3cbc38cf42ca42d2dc9a93c949e0381ff919df71
> [12/19] clk: imx: add support for i.MX8MN anatop clock driver
>         commit: 80badb1d7264e83b512475898e7459f464a009c9
> [13/19] clk: imx: add support for i.MX8MP anatop clock driver
>         commit: 4c82bbe8b5437c7f16b2891ce33210c0f1410597
> [14/19] clk: imx8mp: rename ccm_base to base
>         commit: 1a77907dbbecfbe5e6a1aec28afd49a1dc184b7a
> [16/19] dt-bindings: clock: imx8m-clock: add PLLs
>         commit: 6a55647af3334f1d935ece67de4a838a864b53fc
>
> Best regards,
> --
> Abel Vesa <abel.vesa@...aro.org>



-- 

Dario Binacchi

Senior Embedded Linux Developer

dario.binacchi@...rulasolutions.com

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