From: John Garry <john.garry@huawei.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Sinan Kaya <okaya@kernel.org>, "xuwei (O)" <xuwei5@hisilicon.com>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Jiaxun Yang <jiaxun.yang@flygoat.com>,
linux-arch <linux-arch@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>
Subject: Re: About commit "io: change inX() to have their own IO barrier overrides"
Date: Tue, 3 Mar 2020 17:16:18 +0000 [thread overview]
Message-ID: <773c5d63-5626-ca3d-634b-73d3a7776ddb@huawei.com> (raw)
In-Reply-To: <CAK8P3a0f9hnKGd6GJ8qFZSu+J-n4fY23TCGxQkmgJaxbpre50Q@mail.gmail.com>
On 03/03/2020 16:40, Arnd Bergmann wrote:
> On Tue, Mar 3, 2020 at 2:18 PM John Garry <john.garry@huawei.com> wrote:
>>
>> + linux-arch
>>
>> For background, see
>> https://lore.kernel.org/lkml/2e80d7bc-32a0-cc40-00a9-8a383a1966c2@huawei.com/
>>
>>>>
>>>> So today only ARM64 uses it for this relevant code, above. But maybe
>>>> others in future will want to use it - any arch without native IO port
>>>> access is a candidate.
>>>
>>> I'm looking at Arnd here for help.
>>>
>>>>
>>>>>
>>>>> As long as the expectations are set, I see no reason why it shouldn't
>>>>> but, I'll let Arnd comment on it too.
>>>>
>>>> ok, so it looks reasonable consider replicating your change for ***, above.
>>
>> To be clear, I would make this change in lib/logic_pio.c since
>> __io_pbr() can be overridden per-arch:
>>
>> #define BUILD_LOGIC_IO(bw, type)
>> type logic_in##bw(unsigned long addr)
>> {
>> type ret = (type)~0;
>> if (addr < MMIO_UPPER_LIMIT) {
>> - ret = read##bw(PCI_IOBASE + addr);
>> + __io_pbr();
>> + ret = __raw_read##bw(PCI_IOBASE + addr);
>> + __io_pbr();
>
> __io_par();
>
>> } else if (addr >= MMIO_UPPER_LIMIT && addr < IO_SPACE_LIMIT) {
>> struct logic_pio_hwaddr *entry = find_io_range(addr);
>>
>> ...
>>
>> (forgetting leX_to_cpu for the moment)
>
> Yes, I suppose this is required to get consistent behavior on arm64,
> which overrides __io_par() but not __io_ar(), with the current code
> the barrier after read is weaker when LOGIC_PIO is enabled than it
> is otherwise.
Ok.
Apart from that, this code is somewhat hidden. I mean, most people would
consider generic IO port accessors come from asm-generic/io.h only,
which is not the case here. Maybe this can be better integrated into
asm-generic/io.h, the only hint today being the logic_pio.h include half
way through the file.
>
> For other architectures, I suppose we would need another indirection
> level, as those can also override the default inb() itself to do something
> other than readb(PCI_IOBASE + addr), and that is not handled
> here either. We can do that if we need LOGIC_PIO on a second
> architecture.
Jiaxun Yang did mention that MIPS may want to move away from its own IO
space management.
Thanks,
John
next prev parent reply other threads:[~2020-03-03 17:16 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-28 9:52 About commit "io: change inX() to have their own IO barrier overrides" John Garry
2020-02-28 23:57 ` Sinan Kaya
2020-03-02 12:35 ` John Garry
2020-03-02 16:44 ` Sinan Kaya
2020-03-03 13:18 ` John Garry
2020-03-03 16:40 ` Arnd Bergmann
2020-03-03 17:16 ` John Garry [this message]
2020-03-06 3:44 ` Sinan Kaya
2020-03-06 7:54 ` Arnd Bergmann
2020-03-06 10:39 ` John Garry
2020-03-06 15:16 ` Arnd Bergmann
2020-03-06 16:18 ` John Garry
2020-03-06 16:29 ` Arnd Bergmann
2020-03-06 16:43 ` John Garry
2020-03-11 16:12 ` John Garry
2020-03-06 21:15 ` Sinan Kaya
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