linux-kernel - Re: [PATCH v3 1/3] PCI/pwrctrl: Add optional slot clock to pwrctrl driver for PCI slots

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Message-ID: <CAMuHMdU=+Hxz09DJeVOhZ1N5yS=UJgMsr5R40KBeu=ftoq4zrw@mail.gmail.com>
Date: Mon, 16 Jun 2025 14:02:34 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Marek Vasut <marek.vasut+renesas@...lbox.org>, Bartosz Golaszewski <brgl@...ev.pl>, 
	linux-arm-kernel@...ts.infradead.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, Anand Moon <linux.amoon@...il.com>, 
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Conor Dooley <conor+dt@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Magnus Damm <magnus.damm@...il.com>, Rob Herring <robh@...nel.org>, 
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v3 1/3] PCI/pwrctrl: Add optional slot clock to pwrctrl
 driver for PCI slots

Hi Bjorn,

On Sat, 14 Jun 2025 at 00:01, Bjorn Helgaas <helgaas@...nel.org> wrote:
> On Thu, Jun 12, 2025 at 03:16:45PM +0200, Geert Uytterhoeven wrote:
> > On Sat, 7 Jun 2025 at 21:46, Marek Vasut
> > <marek.vasut+renesas@...lbox.org> wrote:
> > > Add the ability to enable optional slot clock into the pwrctrl driver.
> > > This is used to enable slot clock in split-clock topologies, where the
> > > PCIe host/controller supply and PCIe slot supply are not provided by
> > > the same clock. The PCIe host/controller clock should be described in
> > > the controller node as the controller clock, while the slot clock should
> > > be described in controller bridge/slot subnode.
> > >
> > > Example DT snippet:
> > > &pcicontroller {
> > >     clocks = <&clk_dif 0>;             /* PCIe controller clock */
> > >
> > >     pci@0,0 {
> > >         #address-cells = <3>;
> > >         #size-cells = <2>;
> > >         reg = <0x0 0x0 0x0 0x0 0x0>;
> > >         compatible = "pciclass,0604";
> > >         device_type = "pci";
> > >         clocks = <&clk_dif 1>;         /* PCIe slot clock */
> > >         vpcie3v3-supply = <&reg_3p3v>;
> > >         ranges;
> > >     };
> > > };
> > >
> > > Example clock topology:
> > >  ____________                    ____________
> > > |  PCIe host |                  | PCIe slot  |
> > > |            |                  |            |
> > > |    PCIe RX<|==================|>PCIe TX    |
> > > |    PCIe TX<|==================|>PCIe RX    |
> > > |            |                  |            |
> > > |   PCIe CLK<|======..  ..======|>PCIe CLK   |
> > > '------------'      ||  ||      '------------'
> > >                     ||  ||
> > >  ____________       ||  ||
> > > |  9FGV0441  |      ||  ||
> > > |            |      ||  ||
> > > |   CLK DIF0<|======''  ||
> > > |   CLK DIF1<|==========''
> > > |   CLK DIF2<|
> > > |   CLK DIF3<|
> > > '------------'
> > >
> > > Acked-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> > > Reviewed-by: Anand Moon <linux.amoon@...il.com>
> > > Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > > Signed-off-by: Marek Vasut <marek.vasut+renesas@...lbox.org>
> >
> > Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
> >
> > Bartosz: Any chance you can apply this patch to an immutable branch,
> > so I can merge that before taking the other two patches?
> > The alternative is to postpone the DTS patches for one cycle.
>
> I applied this patch only to pci/pwrctrl for v6.17 and made a note
> that the commit should be immutable:
>
>   66db1d3cbdb0 ("PCI/pwrctrl: Add optional slot clock for PCI slots")
>
> We will likely add other pwrctrl patches to this branch during this
> cycle; I assume that will be OK as long as 66db1d3cbdb0 remains
> untouched, right?

Great, I will merge that branch, and will apply the DTS patches on top.
Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds