From: Wulf Hofbauer <wh@echo.chem.tu-berlin.de>
To: linuxppc-dev@lists.linuxppc.org
Subject: yet another bug in atyfb.c
Date: Tue, 3 Aug 99 12:21:54 MESZ [thread overview]
Message-ID: <E11BbjL-0004vi-00@mail.zrz.tu-berlin.de> (raw)
ABSTRACT: atyfb.c doesn't work when compiled with gcc-2.95 due to incorrect
inline assembly code.
EXPLANATION: atyfb.c - as of Kernel 2.2.10 - uses the following constructs
for accessing little-endian words in Mach32 controller space:
asm("lwbrx %0,%1,%2" : "=r"(val) : "r" (regindex), "r" (temp));
and
asm("stwbrx %0,%1,%2" : : "r" (val), "r" (regindex), "r" (temp) :
"memory");
This is meant to access a word at address regindex+temp. If regindex
happens to be held in register r0, the address calculation is off as
r0 is defined as a null operand. This problem shows up with gcc-2.95 which
seems to use better register allocation code and _does_ keep regindex in
r0 at times.
The way of how the respective functions aty_ld_le32 and aty_st_le32
seems also strange to me, and I suspect it is incorrect.
Here's a proposed fix that works for me. I also changed the sparc code
to honour volatility of IO space, but couldn't check if this affects
the kernel. It would be nice if someone familiar with sparc could have a
look at this.
Here's the fix:
--- atyfb.c.orig Wed Jul 21 00:04:40 1999
+++ atyfb.c Tue Aug 3 12:13:42 1999
@@ -466,18 +466,18 @@
};
-static inline u32 aty_ld_le32(volatile unsigned int regindex,
+static inline u32 aty_ld_le32(unsigned int regindex,
const struct fb_info_aty *info)
{
unsigned long temp;
u32 val;
#if defined(__powerpc__)
- temp = info->ati_regbase;
- asm("lwbrx %0,%1,%2" : "=r"(val) : "r" (regindex), "r" (temp));
+ temp = info->ati_regbase+regindex;
+ asm("lwbrx %0,0,%1" : "=r" (val) : "r" ((volatile u32*)temp), "m" (*(volatile u32*)temp));
#elif defined(__sparc_v9__)
temp = info->ati_regbase + regindex;
- asm("lduwa [%1] %2, %0" : "=r" (val) : "r" (temp), "i" (ASI_PL));
+ asm("lduwa [%1] %2, %0" : "=r" (val) : "r" ((volatile u32*)temp), "i" (ASI_PL));
#else
temp = info->ati_regbase+regindex;
val = le32_to_cpu(*((volatile u32 *)(temp)));
@@ -485,18 +485,17 @@
return val;
}
-static inline void aty_st_le32(volatile unsigned int regindex, u32 val,
+static inline void aty_st_le32(unsigned int regindex, u32 val,
const struct fb_info_aty *info)
{
unsigned long temp;
#if defined(__powerpc__)
- temp = info->ati_regbase;
- asm("stwbrx %0,%1,%2" : : "r" (val), "r" (regindex), "r" (temp) :
- "memory");
+ temp = info->ati_regbase+regindex;
+ asm("stwbrx %1,0,%2" : "=m" (*(volatile u32*)temp) : "r" (val) , "r" ((volatile u32*)temp));
#elif defined(__sparc_v9__)
temp = info->ati_regbase + regindex;
- asm("stwa %0, [%1] %2" : : "r" (val), "r" (temp), "i" (ASI_PL) : "memory");
+ asm("stwa %0, [%1] %2" : : "r" (val), "r" ((volatile u32*)temp), "i" (ASI_PL) : "memory");
#else
temp = info->ati_regbase+regindex;
*((volatile u32 *)(temp)) = cpu_to_le32(val);
- Wulf
--
________________________________________________________
! Dipl. Phys. Wulf Hofbauer (wh@echo.chem.tu-berlin.de) !
! Max-Volmer-Institut Technische Universitaet Berlin !
! Strasse des 17. Juni 135 10623 Berlin Germany !
!________________________________________________________!
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next reply other threads:[~2018-09-28 16:27 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-28 16:27 Wulf Hofbauer [this message]
1999-08-03 15:26 ` yet another bug in atyfb.c David Edelsohn
1999-08-03 16:57 ` Daniel Jacobowitz
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