linux-kernel - Re: [PATCH pci] PCI: don't skip probing entire device if first fn OF node has status = "disabled"

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Date:   Fri, 2 Jun 2023 13:16:28 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Jianmin Lv <lvjianmin@...ngson.cn>
Cc:     Liu Peibao <liupeibao@...ngson.cn>,
        Bjorn Helgaas <helgaas@...nel.org>, linux-pci@...r.kernel.org,
        netdev@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh@...nel.org>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Michael Walle <michael@...le.cc>, linux-kernel@...r.kernel.org,
        Binbin Zhou <zhoubinbin@...ngson.cn>,
        Huacai Chen <chenhuacai@...ngson.cn>
Subject: Re: [PATCH pci] PCI: don't skip probing entire device if first fn OF
 node has status = "disabled"

Hi Jianmin,

On Fri, Jun 02, 2023 at 03:36:18PM +0800, Jianmin Lv wrote:
> On 2023/6/2 下午3:21, Liu Peibao wrote:
> > Hi all,
> > 
> > It seems that modification for current PCI enumeration framework is
> > needed to solve the problem. If the effect of this modification is not
> > easy to evaluate, for the requirement of Loongson, it should be OK that
> > do the things in Loongson PCI controller driver like discussed
> > before[1].
> > 
> > Br,
> > Peibao
> > 
> > [1] https://lore.kernel.org/all/20221114074346.23008-1-liupeibao@loongson.cn/
> > 
> 
> Agree. For current pci core code, all functions of the device will be
> skipped if function 0 is not found, even without the patch 6fffbc7ae137
> (e.g. the func 0 is disabled in bios by setting pci header to 0xffffffff).
> So it seems that there are two ways for the issue:
> 
> 1. Adjust the pci scan core code to allow separate function to be
> enumerated, which will affect widely the pci core code.
> 2. Only Adjust loongson pci controller driver as Peibao said, and any
> function of the device should use platform device in DT if function 0 is
> disabled, which is acceptable for loongson.
> 
> Thanks,
> Jianmin

How about 3. handle of_device_is_available() in the probe function of
the "loongson, pci-gmac" driver? Would that not work?