linux-kernel - Re: [PATCH V6] PCI: loongson: Skip scanning disabled child devices

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Date:   Thu, 9 Feb 2023 14:12:09 +0800
From:   Huacai Chen <chenhuacai@...nel.org>
To:     Binbin Zhou <zhoubinbin@...ngson.cn>
Cc:     Liu Peibao <liupeibao@...ngson.cn>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Huacai Chen <chenhuacai@...ngson.cn>,
        Jianmin Lv <lvjianmin@...ngson.cn>,
        Yinbo Zhu <zhuyinbo@...ngson.cn>,
        wanghongliang <wanghongliang@...ngson.cn>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V6] PCI: loongson: Skip scanning disabled child devices

On Wed, Feb 8, 2023 at 11:00 AM Binbin Zhou <zhoubinbin@...ngson.cn> wrote:
>
>
> 在 2022/11/17 10:09, Liu Peibao 写道:
> > Add a mechanism to disable on chip PCI devices by DT. Typically, when there
> > are pins shareable between the platform device and the on chip PCI device,
> > if the PCI device is not preferred, add `status = "disabled"` property to
> > this PCI device DT node.
> >
> > For example, on LS2K1000, GMAC1 (on chip PCI device) and GPIO (platform
> > device, not PCI device) 14 share the same pin. If GMAC1 is not preferred,
> > add `status = "disabled"` property in GMAC1 DT node.
> >
> > Signed-off-by: Liu Peibao <liupeibao@...ngson.cn>
> Tested-by: Binbin Zhou <zhoubinbin@...ngson.cn>
Acked-by: Huacai Chen <chenhuacai@...ngson.cn>


> > ---
> > V5 -> V6: 1. rewrite the commit log to make things clear.
> >         2. replace "unavailable" as "disabled" in patch subject.
> > V4 -> V5: clear the issue we are facing in commit log.
> > V3 -> V4: 1. get rid of the masklist and search the status property
> >         directly.
> >            2. check the status property only when accessing the vendor ID.
> > V2 -> V3: 1. use list_for_each_entry() for more clearly.
> >            2. fix wrong use of sizeof().
> > V1 -> V2: use existing property "status" instead of adding new property.
> >
> >   drivers/pci/controller/pci-loongson.c | 11 +++++++++++
> >   1 file changed, 11 insertions(+)
> >
> > diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
> > index 05c50408f13b..efca0b3b5a29 100644
> > --- a/drivers/pci/controller/pci-loongson.c
> > +++ b/drivers/pci/controller/pci-loongson.c
> > @@ -194,6 +194,17 @@ static void __iomem *pci_loongson_map_bus(struct pci_bus *bus,
> >                       return NULL;
> >       }
> >
> > +#ifdef CONFIG_OF
> > +     /* Don't access disabled devices. */
> > +     if (pci_is_root_bus(bus) && where == PCI_VENDOR_ID) {
> > +             struct device_node *dn;
> > +
> > +             dn = of_pci_find_child_device(bus->dev.of_node, devfn);
> > +             if (dn && !of_device_is_available(dn))
> > +                     return NULL;
> > +     }
> > +#endif
> > +
> >       /* CFG0 can only access standard space */
> >       if (where < PCI_CFG_SPACE_SIZE && priv->cfg0_base)
> >               return cfg0_map(priv, bus, devfn, where);
>