linux-kernel - Re: [PATCH v4 1/3] lib: logic_pio: Use logical PIO low-level accessors for !CONFIG_INDIRECT

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Date:   Fri, 14 Jun 2019 06:50:56 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     John Garry <john.garry@...wei.com>
Cc:     lorenzo.pieralisi@....com, arnd@...db.de,
        linux-pci@...r.kernel.org, rjw@...ysocki.net,
        linux-arm-kernel@...ts.infradead.org, will.deacon@....com,
        wangkefeng.wang@...wei.com, linuxarm@...wei.com,
        andriy.shevchenko@...ux.intel.com, linux-kernel@...r.kernel.org,
        catalin.marinas@....com
Subject: Re: [PATCH v4 1/3] lib: logic_pio: Use logical PIO low-level
 accessors for !CONFIG_INDIRECT_PIO

On Fri, Jun 14, 2019 at 10:02:52AM +0100, John Garry wrote:
> On 13/06/2019 21:09, Bjorn Helgaas wrote:
> > On Thu, Jun 13, 2019 at 10:39:12AM +0100, John Garry wrote:
> > > On 13/06/2019 03:39, Bjorn Helgaas wrote:
> > > > I'm not sure it's even safe, because CONFIG_INDIRECT_PIO depends on
> > > > ARM64,  but PCI_IOBASE is defined on most arches via asm-generic/io.h,
> > > > so this potentially affects arches other than ARM64.
> > > 
> > > It would do. It would affect any arch which defines PCI_IOBASE and
> > > does not have arch-specific definition of inb et all.
> 
> > What's the reason for testing PCI_IOBASE instead of
> > CONFIG_INDIRECT_PIO?  If there's a reason it's needed, that's fine,
> > but it does make this much more complicated to review.
> 
> For ARM64, we have PCI_IOBASE defined but may not have
> CONFIG_INDIRECT_PIO defined. Currently CONFIG_INDIRECT_PIO is only
> selected by CONFIG_HISILICON_LPC.
> 
> As such, we should make this change also for when
> CONFIG_INDIRECT_PIO is not defined.

OK.  This is all very important for the commit log -- we need to
understand what arches are affected and the reason they need it.

Since the goal of this series is to fix an ARM64-specific issue, and
the typical port I/O model is for each arch to #define its own inb(),
maybe it would make sense to move the "#define inb logic_inb" from
linux/logic_pio.h to arm64/include/asm/io.h?

The "#ifndef inb" arrangement gets pretty complicated when it occurs
more than one place (asm-generic/io.h and logic_pio.h) and we have to
start worrying about the ordering of #includes.

Bjorn