linux-kernel - Re: [PATCH 09/12] unicore32 machine related files: hardware registers

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Message-Id: <201102171759.45365.arnd@arndb.de>
Date:	Thu, 17 Feb 2011 17:59:45 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	"Guan Xuetao" <gxt@...c.pku.edu.cn>
Cc:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	"'Greg KH'" <greg@...ah.com>
Subject: Re: [PATCH 09/12] unicore32 machine related files: hardware registers

On Wednesday 16 February 2011, Guan Xuetao wrote:
> +#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)

> #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.

- 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.

- 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

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)

	Arnd

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