Re: [PATCH 1/1] edac x38: new MC driver module

Hitoshi Mitake
2008-11-29T13:25:13Z

On Sat, 29 Nov 2008 11:52:29 +0100
Sam Ravnborg <sam@ravnborg.org> wrote:

> >
> > But this is old way. ARCH_HAS_READQ and ARCH_HAS_WRITEQ are new ways
> > to determine existence of readq/writeq. Drivers which use readq/writeq should
> > depend on these values in their Kconfig file.
>
> If we look at arch/x86/Kconfig we see:
> ### Arch settings
> config X86
> def_bool y
> select HAVE_AOUT if X86_32
> select HAVE_UNSTABLE_SCHED_CLOCK
> select HAVE_IDE
> select HAVE_OPROFILE
> select HAVE_IOREMAP_PROT
> select HAVE_KPROBES
> select ARCH_WANT_OPTIONAL_GPIOLIB
> ...
>
> So the normal syntax here is "HAVE_XXX_XXX" - not ARCH_HAS_XXX_XXX
>
> If you update your patch please use this syntax,
> and locate the select under X86 - not under the 32/64 entries.

Thanks for your notification. I didn't notice that syntax rule.

>
> But I do not see why adding these in the first place.
>

Andrew Morton told that drivers which need readq/writeq should use ones of kernel,
and if architecture part of kernel does not provide readq/writeq, drivers should be disabled.

This is Andrew's mail:
http://marc.info/?l=linux-kernel&m=122625885124798&w=2
===> Quote:

#ifdef readq

Is a suitable way of determining whether the architecture implements
readq and writeq. It isn't pretty, but it will suffice.

A problem with it is that drivers will then do

#ifndef readq
<provide a local implementation here>
#endif

which rather sucks - we don't want lots of little private readq/writeq
implementations all over the tree.

Perhaps it would be better to have a CONFIG_ARCH_HAS_READQ and to then
disable these drivers on the architectures which don't provide
readq/writeq support.

<====

This is new patch.

description of this patch
Adding implementation of readq/writeq to x86_32,
and adding config value to x86 architecture to determine existence of readq/writeq

Signed-off-by: Hitoshi Mitake <h.mitake@gmail.com>
---
arch/x86/Kconfig | 2 ++
arch/x86/include/asm/io.h | 24 ++++++++++++++++++++++++
2 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ac22bb7..75408fe 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -34,6 +34,8 @@ config X86
select HAVE_ARCH_TRACEHOOK
select HAVE_GENERIC_DMA_COHERENT if X86_32
select HAVE_EFFICIENT_UNALIGNED_ACCESS
+ select HAVE_READQ
+ select HAVE_WRITEQ

config ARCH_DEFCONFIG
string
diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index ac2abc8..ddc67aa 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -4,6 +4,7 @@
#define ARCH_HAS_IOREMAP_WC

#include <linux/compiler.h>
+#include <asm-generic/int-ll64.h>

#define build_mmio_read(name, size, type, reg, barrier) \
static inline type name(const volatile void __iomem *addr) \
@@ -57,6 +58,29 @@ build_mmio_write(__writeq, "q", unsigned long, "r", )
/* Let people know we have them */
#define readq readq
#define writeq writeq
+
+#else /* CONFIG_X86_32 from here */
+
+static inline __u64 readq(const volatile void __iomem *addr)
+{
+ const volatile u32 __iomem *p = addr;
+ u32 l, h;
+
+ l = readl(p);
+ h = readl(p+1);
+
+ return l + ((u64)h << 32);
+}
+
+static inline void writeq(__u64 val, volatile void __iomem *addr)
+{
+ writel(val, addr);
+ writel(val >> 32, addr+4);
+}
+
+#define readq readq
+#define writeq writeq
+
#endif

extern int iommu_bio_merge;
--
1.5.6.5