linux-kernel - Re: [PATCH 1/2] PCI/pwrctrl: Add optional slot clock to pwrctrl driver for PCI slots

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Message-ID: <rvfkojyooqg7unr4i2izx4hmb24ppsx7tn65pbtfmlbrga76iu@dvsg74hlspzu>
Date: Wed, 28 May 2025 09:17:36 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Marek Vasut <marek.vasut+renesas@...lbox.org>
Cc: linux-arm-kernel@...ts.infradead.org, 
	Bartosz Golaszewski <brgl@...ev.pl>, 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 1/2] PCI/pwrctrl: Add optional slot clock to pwrctrl
 driver for PCI slots

On Sun, May 25, 2025 at 06:04:03PM +0200, Marek Vasut 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<|
> '------------'
> 
> Signed-off-by: Marek Vasut <marek.vasut+renesas@...lbox.org>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

- Mani

> ---
> Cc: Bartosz Golaszewski <brgl@...ev.pl>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: Conor Dooley <conor+dt@...nel.org>
> Cc: Geert Uytterhoeven <geert+renesas@...der.be>
> Cc: Krzysztof Kozlowski <krzk+dt@...nel.org>
> Cc: Magnus Damm <magnus.damm@...il.com>
> Cc: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> Cc: Rob Herring <robh@...nel.org>
> Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
> Cc: devicetree@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Cc: linux-pci@...r.kernel.org
> Cc: linux-renesas-soc@...r.kernel.org
> ---
>  drivers/pci/pwrctrl/slot.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/pci/pwrctrl/slot.c b/drivers/pci/pwrctrl/slot.c
> index 18becc144913e..222c14056cfae 100644
> --- a/drivers/pci/pwrctrl/slot.c
> +++ b/drivers/pci/pwrctrl/slot.c
> @@ -4,6 +4,7 @@
>   * Author: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
>   */
>  
> +#include <linux/clk.h>
>  #include <linux/device.h>
>  #include <linux/mod_devicetable.h>
>  #include <linux/module.h>
> @@ -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 = PTR_ERR(clk);
> +		dev_err_probe(dev, ret, "Failed to enable slot clock\n");
> +		goto err_regulator_disable;
> +	}
> +
>  	ret = devm_add_action_or_reset(dev, devm_pci_pwrctrl_slot_power_off,
>  				       slot);
>  	if (ret)
> -- 
> 2.47.2
> 

-- 
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