linux-kernel - Re: [PATCH v2 1/3] PCI/pwrctrl: Add optional slot clock to pwrctrl driver for PCI slots

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Message-ID: <CAMuHMdUFHKHKfymqa6jwfNnxZTAuH3kbj5WL+-zN=TR6XGd0eA@mail.gmail.com>
Date: Wed, 4 Jun 2025 10:40:25 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
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>, Bartosz Golaszewski <brgl@...ev.pl>, 
	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 v2 1/3] PCI/pwrctrl: Add optional slot clock to pwrctrl
 driver for PCI slots

Hi Marek,

Thanks for your patch!

On Sat, 31 May 2025 at 00:55, 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 */

I assume this should be documented in
dtschema/schemas/pci/pci-bus-common.yaml, too?

>         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<|
> '------------'
>
> 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>

> --- a/drivers/pci/pwrctrl/slot.c
> +++ b/drivers/pci/pwrctrl/slot.c

> @@ -30,6 +31,7 @@ static int pci_pwrctrl_slot_probe(struct platform_device *pdev)
>  {
>         struct pci_pwrctrl_slot_data *slot;
>         struct device *dev = &pdev->dev;
> +       struct clk *clk;
>         int ret;
>
>         slot = devm_kzalloc(dev, sizeof(*slot), GFP_KERNEL);
> @@ -50,6 +52,13 @@ static int pci_pwrctrl_slot_probe(struct platform_device *pdev)
>                 goto err_regulator_free;
>         }
>
> +       clk = devm_clk_get_optional_enabled(dev, NULL);
> +       if (IS_ERR(clk)) {
> +               ret = dev_err_probe(dev, PTR_ERR(clk),
> +                                   "Failed to enable slot clock\n");
> +               goto err_regulator_disable;
> +       }

You are adding this block in the middle of the regulator handling.
Please move it below, under the devm_add_action_or_reset() call
(which is handled wrong, I have sent a patch[1]).

> +
>         ret = devm_add_action_or_reset(dev, devm_pci_pwrctrl_slot_power_off,
>                                        slot);
>         if (ret)

[1] https://lore.kernel.org/f60c445e965ba309f08c33de78bd62f358e68cd0.1749025687.git.geert+renesas@glider.be

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