linux-kernel - Re: [PATCH 1/2] clk: sunxi-ng: v3s: Fix de clock definition

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Message-ID: <aGhNFe3wGLX8aUC6@collins>
Date: Fri, 4 Jul 2025 23:52:21 +0200
From: Paul Kocialkowski <paulk@...-base.io>
To: Icenowy Zheng <uwu@...nowy.me>
Cc: linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	Samuel Holland <samuel@...lland.org>,
	Icenowy Zheng <icenowy@...c.xyz>,
	Maxime Ripard <mripard@...nel.org>
Subject: Re: [PATCH 1/2] clk: sunxi-ng: v3s: Fix de clock definition

Hi,

Le Fri 04 Jul 25, 23:54, Icenowy Zheng a écrit :
> 在 2025-07-04星期五的 17:40 +0200，Paul Kocialkowski写道：
> > The de clock is marked with CLK_SET_RATE_PARENT, which is really not
> > necessary (as confirmed from experimentation) and significantly
> > restricts flexibility for other clocks using the same parent.
> 
> With it not setting parent, is arbitary pixel clocks still possible?

Absolutely and the clock tree is very much improved, I think the flag was the
reason that was preventing it from naturally keeping the tcon and de clocks
under the video pll in my case.

Now it can provide both the 33 Mhz for the pixel clock and runs the mixer at
nearly 150 MHz. The video pll now runs at 297 MHz which is a perfect fit for
csi-sclk camera main clock, so the algorithm is doing its job at its best!

So this means that I no longer have to change the mixer clock to 297 MHz to
keep it under the video pll. It pretty much solves all my problems at once.

Here is the relevant clk_summary extract:
    pll-video                        2       2        2        297000000   50000      0     50000      Y      deviceless                      no_connection_id         
       csi-sclk                      0       0        3        297000000   50000      0     50000      N         1cb8000.isp                     mod                      
                                                                                                                 1cb0000.camera                  mod                      
                                                                                                                 1cb1000.csi                     mod                      
       tcon                          2       2        1        33000000    50000      0     50000      Y         1c0c000.lcd-controller          tcon-ch0                 
          tcon-data-clock            1       1        1        33000000    50000      0     50000      Y            deviceless                      no_connection_id         
       de                            2       2        0        297000000   50000      0     50000      Y         1000000.clock                   mod                      
          wb-div                     0       0        0        297000000   50000      0     50000      Y            deviceless                      no_connection_id         
             wb                      0       0        0        297000000   50000      0     50000      N               deviceless                      no_connection_id         
          mixer0-div                 1       1        0        148500000   50000      0     50000      Y            deviceless                      no_connection_id         
             mixer0                  1       1        0        148500000   50000      0     50000      Y               1100000.mixer                   mod                      

Cheers,

Paul

> > 
> > In addition the source selection (parent) field is marked as using
> > 2 bits, when it the documentation reports that it uses 3.
> > 
> > Fix both issues in the de clock definition.
> > 
> > Fixes: d0f11d14b0bc ("clk: sunxi-ng: add support for V3s CCU")
> > Signed-off-by: Paul Kocialkowski <paulk@...-base.io>
> > ---
> >  drivers/clk/sunxi-ng/ccu-sun8i-v3s.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/drivers/clk/sunxi-ng/ccu-sun8i-v3s.c
> > b/drivers/clk/sunxi-ng/ccu-sun8i-v3s.c
> > index 52e4369664c5..df345a620d8d 100644
> > --- a/drivers/clk/sunxi-ng/ccu-sun8i-v3s.c
> > +++ b/drivers/clk/sunxi-ng/ccu-sun8i-v3s.c
> > @@ -347,8 +347,7 @@ static
> > SUNXI_CCU_GATE(dram_ohci_clk,        "dram-ohci",    "dram",
> >  
> >  static const char * const de_parents[] = { "pll-video", "pll-
> > periph0" };
> >  static SUNXI_CCU_M_WITH_MUX_GATE(de_clk, "de", de_parents,
> > -                                0x104, 0, 4, 24, 2, BIT(31),
> > -                                CLK_SET_RATE_PARENT);
> > +                                0x104, 0, 4, 24, 3, BIT(31), 0);
> >  
> >  static const char * const tcon_parents[] = { "pll-video", "pll-
> > periph0" };
> >  static SUNXI_CCU_M_WITH_MUX_GATE(tcon_clk, "tcon", tcon_parents,
> 

-- 
Paul Kocialkowski,

Independent contractor - sys-base - https://www.sys-base.io/
Free software developer - https://www.paulk.fr/

Expert in multimedia, graphics and embedded hardware support with Linux.

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