linux-kernel - Re: [PATCH V5] PCI: loongson: Skip scanning unavailable child devices

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Message-ID: <3eb09d86.900e.1847534872f.Coremail.chenhuacai@loongson.cn>
Date:   Mon, 14 Nov 2022 16:14:47 +0800 (GMT+08:00)
From:   陈华才 <chenhuacai@...ngson.cn>
To:     "Liu Peibao" <liupeibao@...ngson.cn>
Cc:     "Bjorn Helgaas" <bhelgaas@...gle.com>,
        "Lorenzo Pieralisi" <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        "Jiaxun Yang" <jiaxun.yang@...goat.com>,
        "Christophe JAILLET" <christophe.jaillet@...adoo.fr>,
        "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 V5] PCI: loongson: Skip scanning unavailable child
 devices

Hi, Peibao,


> -----原始邮件-----
> 发件人: "Liu Peibao" <liupeibao@...ngson.cn>
> 发送时间:2022-11-14 15:43:46 (星期一)
> 收件人: "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>
> 抄送: "Huacai Chen" <chenhuacai@...ngson.cn>, "Jianmin Lv" <lvjianmin@...ngson.cn>, "Yinbo Zhu" <zhuyinbo@...ngson.cn>, wanghongliang <wanghongliang@...ngson.cn>, "Liu Peibao" <liupeibao@...ngson.cn>, linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
> 主题: [PATCH V5] PCI: loongson: Skip scanning unavailable child devices
> 
> The PCI Controller of 2K1000 could not mask devices by setting vender ID or
I think this patch is needed by both LS2K500 and LS2K1000, so replace 2K1000 with "LS2K" or "Loongson-2K" or "LS2K500/LS2K1000" maybe better. If new version is needed, please change this, thanks.

Huacai

> device ID in configuration space header as invalid values. When there are
> pins shareable between the platform device and the on chip 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.
> 
> Before this patch, to solve the above problem, we treat the on chip PCI
> devices as platform devices with fixed address assigned by the BIOS. When
> there is device not preferred, add the `status = "disabled"` property in DT
> node. In kernel, the PCI host bridge only scans slot 9/A/B/C/D/E that are
> bridges. Overall, this looks not much elegant.
> 
> Signed-off-by: Liu Peibao <liupeibao@...ngson.cn>
> ---
> V4 -> V5: make the issue we are facing clear 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);
> -- 
> 2.20.1


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