linux-kernel - Re: [PATCH v1 2/6] PCI: brcmstb: Fix error path upon call of regulator_bulk

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Message-ID: <20250206172935.GA990026@bhelgaas>
Date: Thu, 6 Feb 2025 11:29:35 -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 2/6] PCI: brcmstb: Fix error path upon call of
 regulator_bulk_get()

On Wed, Feb 05, 2025 at 02:12:02PM -0500, Jim Quinlan wrote:
> If regulator_bulk_get() returns an error, no regulators are
> created and we need to set their number to zero.  If we do
> not do this and the PCIe link-up fails, regulator_bulk_free()
> will be invoked and effect a panic.
> 
> Also print out the error value, as we cannot return an error
> upwards as Linux will WARN on an error from add_bus().

Wrap all these commit logs to fill 75 columns.  No point in leaving
unused space when most things are formatted to fill 80ish columns or
more.

> 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 | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> index f8fc3d620ee2..bf919467cbcd 100644
> --- a/drivers/pci/controller/pcie-brcmstb.c
> +++ b/drivers/pci/controller/pcie-brcmstb.c
> @@ -1417,7 +1417,8 @@ static int brcm_pcie_add_bus(struct pci_bus *bus)
>  
>  		ret = regulator_bulk_get(dev, sr->num_supplies, sr->supplies);
>  		if (ret) {
> -			dev_info(dev, "No regulators for downstream device\n");
> +			dev_info(dev, "Did not get regulators; err=%d\n", ret);
> +			sr->num_supplies = 0;
>  			goto no_regulators;

I think it might have been better if we could do the
regulator_bulk_get() separately, before pci_host_probe(), so that if 
this error happens, we can deal with it more easily.

Setting num_supplies = 0 is an unusual way of handling this error, and
if this pattern of managing PCIe regulators spreads to other drivers,
we might trip over this again.

Not asking for a redesign here, and maybe it wouldn't even be
possible, but it kind of fits with thinking about splitting Root Port
support from the Root Complex/host bridge support.

Bjorn