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: <zzm2nyrm4nw5di7afe5nxte3hxbx3dvorjg74rsjhl3jlaywp4@x7icn3epnh67>
Date: Wed, 4 Jun 2025 22:52:12 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Marek Vasut <marek.vasut+renesas@...lbox.org>, 
	linux-arm-kernel@...ts.infradead.org, Anand Moon <linux.amoon@...il.com>, 
	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

On Wed, Jun 04, 2025 at 10:40:25AM +0200, Geert Uytterhoeven wrote:
> 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?

You are right.

> 
> >         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]).
> 

Good catch!

- Mani

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