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SubjectRe: [PATCH] lib: 64bit IO

On 1/29/19 6:01 PM, Greg Kroah-Hartman wrote:
> On Tue, Jan 29, 2019 at 05:41:02PM +0200, Vladimir Kondratiev wrote:
>> implement missing io{read|write}64
>> For 64-bit platforms, these 64-bit io functions are defined in
>> include/asm-generic/iomap.h,
>> but actual implementation missing. Provide it.
> What is in include/asm-generic/io.h?
> $ git grep iowrite64be | grep generic
> include/asm-generic/io.h:#ifndef iowrite64be
> include/asm-generic/io.h:#define iowrite64be iowrite64be
> include/asm-generic/io.h:static inline void iowrite64be(u64 value, volatile void __iomem *addr)
> include/asm-generic/iomap.h:extern void iowrite64be(u64, void __iomem *);
> so are you sure this is needed?
> What code is failing to build for you?

The code you mentioned is under

i.e. it works for platforms that does not define CONFIG_GENERIC_IOMAP
This currently defined for quite a lot of platforms, all these should
not use these inlines and use lib/iomap.c - it selected by the same
symbol, from lib/Makefile:

obj-$(CONFIG_GENERIC_IOMAP) += iomap.o

linux$ git grep GENERIC_IOMAP | grep Kconfig
arch/hexagon/Kconfig: select GENERIC_IOMAP
arch/ia64/Kconfig: select GENERIC_IOMAP
arch/m68k/Kconfig: select GENERIC_IOMAP
arch/mips/Kconfig: select GENERIC_IOMAP
arch/openrisc/Kconfig: select GENERIC_IOMAP
arch/powerpc/platforms/Kconfig: select GENERIC_IOMAP
arch/unicore32/Kconfig: select GENERIC_IOMAP
arch/x86/Kconfig: select GENERIC_IOMAP
lib/Kconfig:config GENERIC_IOMAP

Actually, I am using 64-bit MIPS platform for now, and some pieces of
code was not compiling without this patch; but this looks like code all
platforms above need in order to use 64-bit transactions in
"io{redd|write}xx" style

Also, I figured out most platforms does not bother providing PIO in
64-bit quantities, so see below version 2 with MMIO-only implementation.

> thanks,
> greg k-h

From 7f0d31a7cdcc535e0248cb4c4cf8f1d16dc0133d Mon Sep 17 00:00:00 2001
From: Vladimir Kondratiev <>
Date: Thu, 24 Jan 2019 16:59:20 +0200
Subject: [PATCH v2] lib: 64bit IO

implement missing io{read|write}64

For 64-bit platforms, these 64-bit io functions are defined in
but actual implementation missing. Provide it.
Most platforms does not provide 64-bit PIO functions, thus
implement 64-bit transactions as MMIO only

Signed-off-by: Vladimir Kondratiev <>
lib/iomap.c | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)

diff --git a/lib/iomap.c b/lib/iomap.c
index 541d926da95e..86501bccdf72 100644
--- a/lib/iomap.c
+++ b/lib/iomap.c
@@ -67,6 +67,9 @@ static void bad_io_access(unsigned long port, const
char *access)
#ifndef mmio_read16be
#define mmio_read16be(addr) be16_to_cpu(__raw_readw(addr))
#define mmio_read32be(addr) be32_to_cpu(__raw_readl(addr))
+#ifdef CONFIG_64BIT
+#define mmio_read64be(addr) be64_to_cpu(__raw_readq(addr))

unsigned int ioread8(void __iomem *addr)
@@ -100,6 +103,22 @@ EXPORT_SYMBOL(ioread16be);

+#ifdef CONFIG_64BIT
+u64 ioread64(void __iomem *addr)
+ return readq(addr);
+u64 ioread64be(void __iomem *addr)
+ return mmio_read64be(addr);
+#endif /* CONFIG_64BIT */
#ifndef pio_write16be
#define pio_write16be(val,port) outw(swab16(val),port)
#define pio_write32be(val,port) outl(swab32(val),port)
@@ -108,6 +127,9 @@ EXPORT_SYMBOL(ioread32be);
#ifndef mmio_write16be
#define mmio_write16be(val,port) __raw_writew(be16_to_cpu(val),port)
#define mmio_write32be(val,port) __raw_writel(be32_to_cpu(val),port)
+#ifdef CONFIG_64BIT
+#define mmio_write64be(val, port) __raw_writeq(be64_to_cpu(val), port)

void iowrite8(u8 val, void __iomem *addr)
@@ -136,6 +158,22 @@ EXPORT_SYMBOL(iowrite16be);

+#ifdef CONFIG_64BIT
+void iowrite64(u64 val, void __iomem *addr)
+ writeq(val, addr);
+void iowrite64be(u64 val, void __iomem *addr)
+ mmio_write64be(val, addr);
+#endif /* CONFIG_64BIT */
* These are the "repeat MMIO read/write" functions.
* Note the "__raw" accesses, since we don't want to
 \ /
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