> -----Original Message----- > From: Arnd Bergmann [mailto:arnd@xxxxxxxx] > Sent: Friday, February 18, 2011 6:43 PM > To: Guan Xuetao > Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-arch@xxxxxxxxxxxxxxx; 'Greg KH' > Subject: Re: [PATCH 09/12] unicore32 machine related files: hardware registers > > On Friday 18 February 2011 10:52:12 Guan Xuetao wrote: > > > > 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. > > __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. > > Ok, I didn't realize this. However, this is a really bad idea > and I would strongly advise removing this throughout the code. > > The only way we do MMIO accesses in Linux is through the > readl()/writel() functions. On many architectures, these > contain more than just a pointer dereference, and if you > need that, you can change it in just one place. > > Things that can go wrong with volatile pointer dereferences include: > > * compiler turns 32 bit access into four 8-bit accesses > * I/O bus reorders access and it moves outside of a spinlock > * non-volatile accesses to system RAM get reordered around > MMIO access, which may break if the MMIO triggers a DMA. > > > 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 */ > > This change is ok. > > > 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__ > > The result of io_p2v really needs to be a (void __iomem *) pointer, not > an integer, so the accesses can work. > > > # define __REG(x) (*((volatile unsigned long *)io_p2v(x))) > > # define __PREG(x) (io_v2p((unsigned long)&(x))) > > And as explained, these should be removed and all users converted to > use readl()/writel(). I see. I apply the patch as following: arch/unicore32/include/mach/hardware.h | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-) diff --git a/arch/unicore32/include/mach/hardware.h b/arch/unicore32/include/mach/hardware.h index ebce7de..b71405a 100644 --- a/arch/unicore32/include/mach/hardware.h +++ b/arch/unicore32/include/mach/hardware.h @@ -22,8 +22,7 @@ #ifndef __ASSEMBLY__ -# define __REG(x) (*((volatile unsigned long *)io_p2v(x))) -# define __PREG(x) (io_v2p((unsigned long)&(x))) +# define __REG(x) (void __iomem *)io_p2v(x) #endif --- __REG reserved only for all registers prefix. And all using for __REG converted to readl/writel. > > Arnd Thanks Arnd Guan Xuetao -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
