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Message-ID: <20221110210731.GA672063@bhelgaas>
Date: Thu, 10 Nov 2022 15:07:31 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Liu Peibao <liupeibao@...ngson.cn>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Lorenzo Pieralisi <lpieralisi@...nel.org>,
Krzysztof WilczyĆski <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>, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4] PCI: loongson: Skip scanning unavailable child devices
On Tue, Nov 08, 2022 at 02:42:40PM +0800, Liu Peibao wrote:
> The PCI Controller of 2k1000 could not mask devices by setting vender ID or
> device ID in configuration space header as invalid values. When there are
> pins shareable between the platform device and PCI device, if the platform
> device is preferred, we should not scan this PCI device. In the above
> scene, add `status = "disabled"` property in DT node of this PCI device.
>
> Signed-off-by: Liu Peibao <liupeibao@...ngson.cn>
> ---
> 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
Looks nice and simple, thanks for trying this out.
> /* CFG0 can only access standard space */
> if (where < PCI_CFG_SPACE_SIZE && priv->cfg0_base)
> return cfg0_map(priv, bus, devfn, where);
> --
> 2.20.1
>
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