linux-kernel - Re: [PATCH v5 1/6] PCI: OF: Don't remap iospace on unsupported platform

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Message-ID: <D5CC0902-F84F-43F1-88E5-C03018B25050@flygoat.com>
Date:   Sat, 25 Apr 2020 02:03:11 +0800
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     Rob Herring <robh+dt@...nel.org>
CC:     PCI <linux-pci@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Huacai Chen <chenhc@...ote.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Andrew Murray <amurray@...goodpenguin.co.uk>,
        Paul Burton <paulburton@...nel.org>,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "open list:MIPS" <linux-mips@...r.kernel.org>
Subject: Re: [PATCH v5 1/6] PCI: OF: Don't remap iospace on unsupported platform



于 2020年4月25日 GMT+08:00 上午1:47:23, Rob Herring <robh+dt@...nel.org> 写到:
>On Fri, Apr 24, 2020 at 8:09 AM Jiaxun Yang <jiaxun.yang@...goat.com> wrote:
>>
>> There are some platforms that don't support I/O space remapping
>> like MIPS. However, our PCI code will try to remap iospace
>> unconditionally and reject io resources on these platforms.
>>
>> So we should remove I/O space remapping check and use a range
>> check instead on these platforms.
>>
>> Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>
>> --
>> v4: Fix a typo in commit message.
>> v5: Commit message massage
>> ---
>>  drivers/pci/of.c | 9 +++++++++
>>  1 file changed, 9 insertions(+)
>>
>> diff --git a/drivers/pci/of.c b/drivers/pci/of.c
>> index 81ceeaa6f1d5..36e8761b66c6 100644
>> --- a/drivers/pci/of.c
>> +++ b/drivers/pci/of.c
>> @@ -547,12 +547,21 @@ int pci_parse_request_of_pci_ranges(struct device *dev,
>>
>>                 switch (resource_type(res)) {
>>                 case IORESOURCE_IO:
>> +#if defined(PCI_IOBASE) && defined(CONFIG_MMU)
>
>We already have the same condition in pci_remap_iospace(). All this
>does is suppress a WARN. If a WARN is not desired, then change it.
>Perhaps just a single line rather than backtrace would be okay.
>Whether to WARN or not shouldn't be a decision for firmware code.
>
>Though really, if I/O space can never be supported, then it's an error
>in your DT to describe it.

In MIPS world, we do have inb/oub family of I/O functions
to support I/O space. But we're not using remap_iospace as it's breaking
some of our assumptions.
We have our own inb/outb implementation.

In that case, I think make a range check instead of remapping would
be more practical.

Thanks.

>
>>                         err = devm_pci_remap_iospace(dev, res, iobase);
>>                         if (err) {
>>                                 dev_warn(dev, "error %d: failed to map resource %pR\n",
>>                                          err, res);
>>                                 resource_list_destroy_entry(win);
>>                         }
>> +#else
>> +                       /* Simply check if IO is inside the range */
>
>Why do you care if it's never used?
>
>> +                       if (res->end > IO_SPACE_LIMIT) {
>> +                               dev_warn(dev, "resource %pR out of the I/O range\n",
>> +                                       res);
>> +                               resource_list_destroy_entry(win);
>> +                       }
>> +#endif
>>                         break;
>>                 case IORESOURCE_MEM:
>>                         res_valid |= !(res->flags & IORESOURCE_PREFETCH);
>> --
>> 2.26.0.rc2
>>

-- 
Jiaxun Yang