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    SubjectRe: [PATCH v8 02/21] acpi: fix acpi_os_ioremap for arm64
    On Wed, Feb 04, 2015 at 04:08:27PM +0000, Mark Salter wrote:
    > On Wed, 2015-02-04 at 11:25 +0000, Catalin Marinas wrote:
    > > On Tue, Feb 03, 2015 at 05:29:36PM +0000, Mark Salter wrote:
    > > > On Mon, 2015-02-02 at 23:14 +0100, Rafael J. Wysocki wrote:
    > > > > On Monday, February 02, 2015 08:45:30 PM Hanjun Guo wrote:
    > > > > > From: Mark Salter <msalter@redhat.com>
    > > > > >
    > > > > > The acpi_os_ioremap() function may be used to map normal RAM or IO
    > > > > > regions. The current implementation simply uses ioremap_cache(). This
    > > > > > will work for some architectures, but arm64 ioremap_cache() cannot be
    > > > > > used to map IO regions which don't support caching. So for arm64, use
    > > > > > ioremap() for non-RAM regions.
    > > > > >
    > > > > > CC: Rafael J Wysocki <rjw@rjwysocki.net>
    > > > > > Signed-off-by: Mark Salter <msalter@redhat.com>
    > > > > > Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
    > > > > > ---
    > > > > > include/acpi/acpi_io.h | 6 ++++++
    > > > > > 1 file changed, 6 insertions(+)
    > > > > >
    > > > > > diff --git a/include/acpi/acpi_io.h b/include/acpi/acpi_io.h
    > > > > > index 444671e..9d573db 100644
    > > > > > --- a/include/acpi/acpi_io.h
    > > > > > +++ b/include/acpi/acpi_io.h
    > > > > > @@ -1,11 +1,17 @@
    > > > > > #ifndef _ACPI_IO_H_
    > > > > > #define _ACPI_IO_H_
    > > > > >
    > > > > > +#include <linux/mm.h>
    > > > > > #include <linux/io.h>
    > > > > >
    > > > > > static inline void __iomem *acpi_os_ioremap(acpi_physical_address phys,
    > > > > > acpi_size size)
    > > > > > {
    > > > > > +#ifdef CONFIG_ARM64
    > > > > > + if (!page_is_ram(phys >> PAGE_SHIFT))
    > > > > > + return ioremap(phys, size);
    > > > > > +#endif
    > > > >
    > > > > I don't want to see #ifdef CONFIG_ARM64 in this file.
    > > >
    > > > How about something like:
    > > >
    > > > From: Mark Salter <msalter@redhat.com>
    > > > Date: Tue, 3 Feb 2015 10:51:16 -0500
    > > > Subject: [PATCH] acpi: fix acpi_os_ioremap for arm64
    > > >
    > > > The acpi_os_ioremap() function may be used to map normal RAM or IO
    > > > regions. The current implementation simply uses ioremap_cache(). This
    > > > will work for some architectures, but arm64 ioremap_cache() cannot be
    > > > used to map IO regions which don't support caching. So for arm64, use
    > > > ioremap() for non-RAM regions.
    > > >
    > > > CC: Rafael J Wysocki <rjw@rjwysocki.net>
    > > > Signed-off-by: Mark Salter <msalter@redhat.com>
    > > > ---
    > > > arch/arm64/include/asm/acpi.h | 14 ++++++++++++++
    > > > include/acpi/acpi_io.h | 3 +++
    > > > 2 files changed, 17 insertions(+)
    > > >
    > > > diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
    > > > index ea4d2b3..db82bc3 100644
    > > > --- a/arch/arm64/include/asm/acpi.h
    > > > +++ b/arch/arm64/include/asm/acpi.h
    > > > @@ -14,6 +14,7 @@
    > > >
    > > > #include <linux/irqchip/arm-gic-acpi.h>
    > > >
    > > > +#include <linux/mm.h>
    > > > #include <asm/smp_plat.h>
    > > >
    > > > /* Basic configuration for ACPI */
    > > > @@ -100,4 +101,17 @@ static inline bool acpi_psci_use_hvc(void) { return false; }
    > > > static inline void acpi_init_cpus(void) { }
    > > > #endif /* CONFIG_ACPI */
    > > >
    > > > +/*
    > > > + * ACPI table mapping
    > > > + */
    > > > +static inline void __iomem *acpi_os_ioremap(acpi_physical_address phys,
    > > > + acpi_size size)
    > > > +{
    > > > + if (!page_is_ram(phys >> PAGE_SHIFT))
    > > > + return ioremap(phys, size);
    > > > +
    > > > + return ioremap_cache(phys, size);
    > > > +}
    > > > +#define acpi_os_ioremap acpi_os_ioremap
    > >
    > > That's one way of doing this, I'm not too bothered with the approach
    > > (define the function name, an ARCH_HAS macro or a Kconfig option, it's
    > > up to Rafael).
    > >
    > > But a question I already asked is what we need ioremap_cache() for? We
    > > don't use NVS on arm64 yet, so is there anything else requiring
    > > cacheable mapping?
    >
    > acpi_os_remap() is used to map ACPI tables. These tables may be in ram
    > which are already included in the kernel's linear RAM mapping. So we
    > need ioremap_cache to avoid two mappings to the same physical page
    > having different caching attributes.

    What's the call path to acpi_os_ioremap() on such tables already in the
    linear mapping? I can see an acpi_map() function which already takes
    care of the RAM mapping case but there are other cases where
    acpi_os_ioremap() is called directly. For example,
    acpi_os_read_memory(), can it be called on both RAM and I/O?

    --
    Catalin

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