linux-kernel - Re: [PATCH RFC 3/7] pci: Change the parent of the platform devices for child OF nodes

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Date: Mon, 1 Jul 2024 12:54:15 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Krishna chaitanya chundru <quic_krichai@...cinc.com>
Cc: Bartosz Golaszewski <brgl@...ev.pl>,
	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 3/7] pci: Change the parent of the platform devices
 for child OF nodes

"Change the parent" basically says what the C code does.  Can we say
something more specific about what the *purpose* of changing it is?

On Wed, Jun 26, 2024 at 06:07:51PM +0530, Krishna chaitanya chundru wrote:
> Currently the power control driver is child of pci-pci bridge driver,
> this will cause issue when suspend resume is introduced in the pwr
> control driver. If the supply is removed to the endpoint in the

Use "pwrctl" so we can connect them.  Also below.

> power control driver then the config space access initaited by the
> pci-pci bridge driver can cause issues like Timeouts.

s/initaited/initiated/ (or just drop it and say "access by the ...")

> For this reason change the parent to controller from pci-pci bridge.

Add blank line here.

> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> ---
>  drivers/pci/bus.c         | 5 +++--
>  drivers/pci/pwrctl/core.c | 7 ++++++-
>  2 files changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
> index 3e3517567721..eedab4aabd81 100644
> --- a/drivers/pci/bus.c
> +++ b/drivers/pci/bus.c
> @@ -335,6 +335,7 @@ void __weak pcibios_bus_add_device(struct pci_dev *pdev) { }
>  void pci_bus_add_device(struct pci_dev *dev)
>  {
>  	struct device_node *dn = dev->dev.of_node;
> +	struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
>  	int retval;
>  
>  	/*
> @@ -356,9 +357,9 @@ void pci_bus_add_device(struct pci_dev *dev)
>  
>  	pci_dev_assign_added(dev, true);
>  
> -	if (pci_is_bridge(dev)) {
> +	if (pci_is_bridge(dev) && host) {
>  		retval = of_platform_populate(dev->dev.of_node, NULL, NULL,
> -					      &dev->dev);
> +					      host->dev.parent);
>  		if (retval)
>  			pci_err(dev, "failed to populate child OF nodes (%d)\n",
>  				retval);
> diff --git a/drivers/pci/pwrctl/core.c b/drivers/pci/pwrctl/core.c
> index feca26ad2f6a..4c0d0f3b15f8 100644
> --- a/drivers/pci/pwrctl/core.c
> +++ b/drivers/pci/pwrctl/core.c
> @@ -10,6 +10,7 @@
>  #include <linux/pci-pwrctl.h>
>  #include <linux/property.h>
>  #include <linux/slab.h>
> +#include "../pci.h"
>  
>  static int pci_pwrctl_notify(struct notifier_block *nb, unsigned long action,
>  			     void *data)
> @@ -64,18 +65,22 @@ static int pci_pwrctl_notify(struct notifier_block *nb, unsigned long action,
>   */
>  int pci_pwrctl_device_set_ready(struct pci_pwrctl *pwrctl)
>  {
> +	struct pci_bus *bus = pci_find_bus(of_get_pci_domain_nr(pwrctl->dev->parent->of_node), 0);
>  	int ret;
>  
>  	if (!pwrctl->dev)
>  		return -ENODEV;
>  
> +	if (!bus)
> +		return -ENODEV;
> +
>  	pwrctl->nb.notifier_call = pci_pwrctl_notify;
>  	ret = bus_register_notifier(&pci_bus_type, &pwrctl->nb);
>  	if (ret)
>  		return ret;
>  
>  	pci_lock_rescan_remove();
> -	pci_rescan_bus(to_pci_dev(pwrctl->dev->parent)->bus);
> +	pci_rescan_bus(bus);
>  	pci_unlock_rescan_remove();
>  
>  	return 0;
> 
> -- 
> 2.42.0
>