Re: [PATCH v1 2/6] PCI: brcmstb: Fix error path upon call of regulator_bulk_get()

[Bjorn Helgaas <helgaas@kernel.org>]

On Thu, Feb 06, 2025 at 01:22:54PM -0500, Jim Quinlan wrote:
> On Thu, Feb 6, 2025 at 12:29 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
> > 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().

> > > Fixes: 9e6be018b263 ("PCI: brcmstb: Enable child bus device regulators from DT")
> > > Signed-off-by: Jim Quinlan <james.quinlan@broadcom.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.
> 
> Keep in mind that brcm_pcie_add_bus() cannot return a non-zero error
> code, as it will get a WARN() from the caller if it does.
> 
> Would you  accept deallocating the "sr" array and setting it to NULL
> like the following error condition does?  In that way we would not be
> invoking any regulator_bulk_xxxx() functions with nr==0.  I'm really
> wary of moving things around...

Yeah, don't move anything around right now.  My wondering is just
about whether the alloc and bulk_get() could be done earlier, leaving
only the bulk_enable() to be done in brcm_pcie_add_bus().

The alloc and bulk_get() depend on DT things and it's nice to catch
those errors earlier.

Bjorn