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Date:   Thu, 10 Nov 2022 23:00:45 +0000
From:   "Jiaxun Yang" <jiaxun.yang@flygoat.com>
To:     "Bjorn Helgaas" <helgaas@kernel.org>,
        "Liu Peibao" <liupeibao@loongson.cn>
Cc:     "Bjorn Helgaas" <bhelgaas@google.com>,
        "Rob Herring" <robh+dt@kernel.org>,
        "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
        "Lorenzo Pieralisi" <lpieralisi@kernel.org>,
        =?UTF-8?Q?Krzysztof_Wilczy=C5=84ski?= <kw@linux.com>,
        "Christophe JAILLET" <christophe.jaillet@wanadoo.fr>,
        "Huacai Chen" <chenhuacai@loongson.cn>,
        "Jianmin Lv" <lvjianmin@loongson.cn>,
        "Yinbo Zhu" <zhuyinbo@loongson.cn>,
        linux-pci <linux-pci@vger.kernel.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH V4] PCI: loongson: Skip scanning unavailable child devices
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=E5=9C=A82022=E5=B9=B411=E6=9C=8810=E6=97=A5=E5=8D=81=E4=B8=80=E6=9C=88 =
=E4=B8=8B=E5=8D=889:07=EF=BC=8CBjorn Helgaas=E5=86=99=E9=81=93=EF=BC=9A
> 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 pla=
tform
>> device is preferred, we should not scan this PCI device. In the above
>> scene, add `status =3D "disabled"` property in DT node of this PCI de=
vice.
>>=20
>> Signed-off-by: Liu Peibao <liupeibao@loongson.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 proper=
ty.
>>=20
>>  drivers/pci/controller/pci-loongson.c | 11 +++++++++++
>>  1 file changed, 11 insertions(+)
>>=20
>> diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/cont=
roller/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;
>>  	}
>> =20
>> +#ifdef CONFIG_OF
>> +	/* Don't access disabled devices. */
>> +	if (pci_is_root_bus(bus) && where =3D=3D PCI_VENDOR_ID) {
>> +		struct device_node *dn;
>> +
>> +		dn =3D 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.

Should we make this into common PCI code?
I guess Loongson won=E2=80=99t be the last platform having such problem.


>
>>  	/* CFG0 can only access standard space */
>>  	if (where < PCI_CFG_SPACE_SIZE && priv->cfg0_base)
>>  		return cfg0_map(priv, bus, devfn, where);
>> --=20
>> 2.20.1
>>

--=20
- Jiaxun