linux-kernel - Re: [PATCH v1 3/6] PCI: brcmstb: Fix potential premature regluator disabling

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Message-ID: <20250206173259.GA991437@bhelgaas>
Date: Thu, 6 Feb 2025 11:32:59 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Jim Quinlan <james.quinlan@...adcom.com>
Cc: linux-pci@...r.kernel.org, Nicolas Saenz Julienne <nsaenz@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Cyril Brulebois <kibi@...ian.org>,
	Stanimir Varbanov <svarbanov@...e.de>,
	bcm-kernel-feedback-list@...adcom.com, jim2101024@...il.com,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Rob Herring <robh@...nel.org>,
	"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" <linux-rpi-kernel@...ts.infradead.org>,
	"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" <linux-arm-kernel@...ts.infradead.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 3/6] PCI: brcmstb: Fix potential premature regluator
 disabling

In subject,

s/regluator/regulator/

On Wed, Feb 05, 2025 at 02:12:03PM -0500, Jim Quinlan wrote:
> Our system for enabling and disabling regulators is designed to work
> only on the port driver below the root complex.  The conditions to
> discriminate for this case should be the same when we are adding or
> removing the bus.  Without this change the regulators may be disabled
> prematurely when a bus further down the tree is removed.

What did the user do to cause the bus to be removed?  I'm wondering if
we turn off the power while the link is still up.  If we do, how does
it get turned back on?  Does that require a manual rescan, and the
scan of the child bus gets the power turned back on?

> Fixes: 9e6be018b263 ("PCI: brcmstb: Enable child bus device regulators from DT")
> Signed-off-by: Jim Quinlan <james.quinlan@...adcom.com>
> ---
>  drivers/pci/controller/pcie-brcmstb.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> index bf919467cbcd..4f5d751cbdd7 100644
> --- a/drivers/pci/controller/pcie-brcmstb.c
> +++ b/drivers/pci/controller/pcie-brcmstb.c
> @@ -1441,7 +1441,7 @@ static void brcm_pcie_remove_bus(struct pci_bus *bus)
>  	struct subdev_regulators *sr = pcie->sr;
>  	struct device *dev = &bus->dev;
>  
> -	if (!sr)
> +	if (!sr || !bus->parent || !pci_is_root_bus(bus->parent))
>  		return;
>  
>  	if (regulator_bulk_disable(sr->num_supplies, sr->supplies))
> -- 
> 2.43.0
>