linux-kernel - Re: [PATCH RFC 4/7] pci: Add new start_link() & stop

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Date: Wed, 26 Jun 2024 17:07:09 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Krishna chaitanya chundru <quic_krichai@...cinc.com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, 
	Lorenzo Pieralisi <lpieralisi@...nel.org>, Krzysztof Wilczyński <kw@...ux.com>, 
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Jingoo Han <jingoohan1@...il.com>, quic_vbadigan@...cinc.com, quic_skananth@...cinc.com, 
	quic_nitegupt@...cinc.com, linux-arm-msm@...r.kernel.org, 
	linux-pci@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 4/7] pci: Add new start_link() & stop_link function ops

On Wed, Jun 26, 2024 at 2:38 PM Krishna chaitanya chundru
<quic_krichai@...cinc.com> wrote:
>
> Certain devices like QPS615 which uses PCI pwrctl framework
> needs to stop link training before configuring the PCIe device.
>
> As controller driver already enables link training, we need to
> stop the link training by using stop_link and enable them back after
> device is configured by using start_link.
>
> The stop_link() & start_link() be used to keep the link in D3cold &
> D0 before turning off the power of the device.
>
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> ---
>  include/linux/pci.h | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index fb004fd4e889..3892ff7fd536 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -803,6 +803,8 @@ struct pci_ops {
>         void __iomem *(*map_bus)(struct pci_bus *bus, unsigned int devfn, int where);
>         int (*read)(struct pci_bus *bus, unsigned int devfn, int where, int size, u32 *val);
>         int (*write)(struct pci_bus *bus, unsigned int devfn, int where, int size, u32 val);
> +       int (*start_link)(struct pci_bus *bus);
> +       int (*stop_link)(struct pci_bus *bus);
>  };
>

IMO stop_link() should return void.

Bart