linux-kernel - Re: [PATCH v2 4/8] PCI: Change the parent to correctly represent pcie hierarchy

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Message-ID: <20240823072340.qcd6afkgwssr4muw@thinkpad>
Date: Fri, 23 Aug 2024 12:53:40 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Krishna chaitanya chundru <quic_krichai@...cinc.com>
Cc: 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>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	cros-qcom-dts-watchers@...omium.org,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Jingoo Han <jingoohan1@...il.com>, andersson@...nel.org,
	quic_vbadigan@...cinc.com, linux-arm-msm@...r.kernel.org,
	linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v2 4/8] PCI: Change the parent to correctly represent
 pcie hierarchy

On Sat, Aug 03, 2024 at 08:52:50AM +0530, Krishna chaitanya chundru wrote:
> Currently the pwrctl 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
> power control driver then the config space access by the
> pci-pci bridge driver can cause issues like Timeouts.
> 
> For this reason change the parent to controller from pci-pci bridge.
> 

Also, what if the PCIe controller driver tries to access the device? Like for
sending PME_Turn_Off etc... during suspend? I think you should also make sure
that the suspend callback of the pwrctl driver has to happen _after_ the
controller driver.

Still the parent-child hierarchy is not going to change, but only the devlink
part.

- Mani

> Fixes: 4565d2652a37 ("PCI/pwrctl: Add PCI power control core code")
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> ---
>  drivers/pci/bus.c         | 3 ++-
>  drivers/pci/pwrctl/core.c | 9 ++++++++-
>  2 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
> index 55c853686051..15b42f0f588f 100644
> --- a/drivers/pci/bus.c
> +++ b/drivers/pci/bus.c
> @@ -328,6 +328,7 @@ void __weak pcibios_bus_add_device(struct pci_dev *pdev) { }
>   */
>  void pci_bus_add_device(struct pci_dev *dev)
>  {
> +	struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
>  	struct device_node *dn = dev->dev.of_node;
>  	int retval;
>  
> @@ -352,7 +353,7 @@ void pci_bus_add_device(struct pci_dev *dev)
>  
>  	if (dev_of_node(&dev->dev) && pci_is_bridge(dev)) {
>  		retval = of_platform_populate(dev_of_node(&dev->dev), 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..4f2ffa0b0a5f 100644
> --- a/drivers/pci/pwrctl/core.c
> +++ b/drivers/pci/pwrctl/core.c
> @@ -11,6 +11,8 @@
>  #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 +66,23 @@ 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;
>  	int ret;
>  
>  	if (!pwrctl->dev)
>  		return -ENODEV;
>  
> +	bus = pci_find_bus(of_get_pci_domain_nr(pwrctl->dev->parent->of_node), 0);
> +	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;
> 
> -- 
> 2.34.1
> 

-- 
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