From: Arnd Bergmann <arnd@arndb.de>
To: John Garry <john.garry@huawei.com>
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 17:40:07 +0100 [thread overview]
Message-ID: <CAK8P3a0f9hnKGd6GJ8qFZSu+J-n4fY23TCGxQkmgJaxbpre50Q@mail.gmail.com> (raw)
In-Reply-To: <7c955142-1fcb-d99e-69e4-1e0d3d9eb8c3@huawei.com>
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.
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.
Arnd
next prev parent reply other threads:[~2020-03-03 16:40 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 [this message]
2020-03-03 17:16 ` John Garry
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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