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Message-ID: <CAMRc=MckQhB4diiWc+Rtk84PtwaKqr34At3heT0vyAgJ9VA7Hg@mail.gmail.com>
Date: Mon, 2 Jun 2025 12:17:01 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Marek Vasut <marek.vasut+renesas@...lbox.org>
Cc: linux-arm-kernel@...ts.infradead.org, Anand Moon <linux.amoon@...il.com>,
Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
Conor Dooley <conor+dt@...nel.org>, Geert Uytterhoeven <geert+renesas@...der.be>,
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 v2 1/3] PCI/pwrctrl: Add optional slot clock to pwrctrl
driver for PCI slots
On Sat, May 31, 2025 at 12:55 AM 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 = <®_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<|
> '------------'
>
> 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>
> ---
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
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