-----Original Message-----
From: Arnd Bergmann [mailto:arnd@arndb.de]
Sent: Friday, February 18, 2011 1:00 AM
To: Guan Xuetao
Cc: linux-kernel@vger.kernel.org; linux-arch@vger.kernel.org; 'Greg KH'
Subject: Re: [PATCH 09/12] unicore32 machine related files: hardware registers

On Wednesday 16 February 2011, Guan Xuetao wrote:

quoted

+#define io_p2v(x)      ((x) - PKUNITY_IOSPACE_BASE)
+#define io_v2p(x)      ((x) + PKUNITY_IOSPACE_BASE)
+
+#ifndef __ASSEMBLY__
+
+# define __REG(x)      (*((volatile unsigned long *)io_p2v(x)))
+# define __PREG(x)     (io_v2p((unsigned long)&(x)))
+
+#else
+
+# define __REG(x)      io_p2v(x)
+# define __PREG(x)     io_v2p(x)

quoted

#define PKUNITY_IOSPACE_BASE            0x80000000 /* 0x80000000 - 0xFFFFFFFF 2GB */

The typecasts look wrong here:

- "volatile unsigned long*" is not the right pointer type to do I/O on. It
  should instead be "void __iomem *". Please use the "sparse" tool with "make C=1"
  to get warnings about incorrect pointer type accesses.

__REG() macro could be used in both left and right sides of assignment sentence.
This idea is borrowed from arm/sa1100.
When used in left side, __REG is a register port, and when used in right side, 
__REG is just the value of the register.
It is a trick, but very useful. I'd like to remain the macros.

- PKUNITY_IOSPACE_BASE seems to be both a virtual and a physical address, which
  is a bad idea, because it prevents a lot of the checks from working correctly.

PKUNITY_IOSPACE_BASE is only used  for physical-virtual address transformation.
(void *) prefix will introduce type cast error.
In addition,  in unicore32, io space and memory space are all in the same 4G address space,
but only different in address range.

- The __REG/__PREG macros seem to have the same purpose as io_p2v/io_v2p, you
  should not require both.

- The term IOSPACE is confusing, because it normally refers to the PCI PIO
  space, while you mean the SoC's MMIO region

Ok, renamed to PKUNITY_MMIO_BASE.

I would recommend defining these as

#ifndef __ASSEMBLY__
#define PKUNITY_MMIO_VIRT ((void __iomem *)0x80000000)
#else
#define PKUNITY_MMIO_VIRT 0x80000000
#endif

#define io_p2v(x)	((x) - PKUNITY_MMIO_VIRT)
#define io_v2p(x)	((x) + PKUNITY_MMIO_VIRT)

/* please remove the two macros below as soon as all users are changed to use io_p2v */
#define __REG(x) io_p2v(x)
#define __PREG(x) io_v2p(x)

For the reason above, I can only apply the patch as following:

From: GuanXuetao <redacted>
Date: Fri, 18 Feb 2011 18:05:23 +0800
Subject: [PATCH] unicore32: rename PKUNITY_IOSPACE_BASE to PKUNITY_MMIO_BASE
   for the term IOSPACE normally refers to the PCI PIO space,
   and remove unused __REG/__PREG macros when __ASSEMBLY__ defined
   -- by advice with Arnd Bergmann

Signed-off-by: Guan Xuetao <redacted>
---
 arch/unicore32/include/mach/PKUnity.h  |    2 +-
 arch/unicore32/include/mach/hardware.h |    9 ++-------
 2 files changed, 3 insertions(+), 8 deletions(-)

diff --git a/arch/unicore32/include/mach/PKUnity.h b/arch/unicore32/include/mach/PKUnity.h
index 1e13208..39f27f4 100644
--- a/arch/unicore32/include/mach/PKUnity.h
+++ b/arch/unicore32/include/mach/PKUnity.h

@@ -21,7 +21,7 @@
  * Memory Definitions
  */
 #define PKUNITY_SDRAM_BASE		0x00000000 /* 0x00000000 - 0x7FFFFFFF 2GB */
-#define PKUNITY_IOSPACE_BASE            0x80000000 /* 0x80000000 - 0xFFFFFFFF 2GB */
+#define PKUNITY_MMIO_BASE		0x80000000 /* 0x80000000 - 0xFFFFFFFF 2GB */
 #define PKUNITY_PCI_BASE		0x80000000 /* 0x80000000 - 0xBFFFFFFF 1GB */
 #include "regs-pci.h"
 #define PKUNITY_BOOT_ROM2_BASE		0xF4000000 /* 0xF4000000 - 0xF7FFFFFF 64MB */

diff --git a/arch/unicore32/include/mach/hardware.h b/arch/unicore32/include/mach/hardware.h
index 3fb7236..ebce7de 100644
--- a/arch/unicore32/include/mach/hardware.h
+++ b/arch/unicore32/include/mach/hardware.h

@@ -17,19 +17,14 @@
 
 #include "PKUnity.h"
 
-#define io_p2v(x)	((x) - PKUNITY_IOSPACE_BASE)
-#define io_v2p(x)	((x) + PKUNITY_IOSPACE_BASE)
+#define io_p2v(x)	((x) - PKUNITY_MMIO_BASE)
+#define io_v2p(x)	((x) + PKUNITY_MMIO_BASE)
 
 #ifndef __ASSEMBLY__
 
 # define __REG(x)	(*((volatile unsigned long *)io_p2v(x)))
 # define __PREG(x)	(io_v2p((unsigned long)&(x)))
 
-#else
-
-# define __REG(x)	io_p2v(x)
-# define __PREG(x)	io_v2p(x)
-
 #endif
 
 #define PCIBIOS_MIN_IO			0x4000 /* should lower than 64KB */

-- 
1.6.2.2

> 
> 	Arnd

Thanks & Regards.

Guan Xuetao