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E1000 - fixed reading/writing device registers

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- the pointers must be flagged as volatile because otherwise they
  might be "optimized" by a compiler. It is a common good
  practice to access the registers this way, the keyword is in C
  for a reason.

- for instance, in eeprom_eerd() when polling a register the
  compiler, under certain conditions, may decide upon the first
  read and if it does not break the loop it assumes that the
  value is not going to change and thus stays in an infinite
  loop.
This commit is contained in:
Tomas Hruby 2011-07-04 10:46:51 +02:00
parent 170457b73f
commit d75138be00
1 changed files with 2 additions and 2 deletions
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4
drivers/e1000/e1000.c
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@ -878,7 +878,7 @@ uint32_t reg;
assert(reg < 0x1ffff);
/* Read from memory mapped register. */
value = *(u32_t *)(e->regs + reg);
value = *(volatile u32_t *)(e->regs + reg);
/* Return the result. */
return value;
@ -896,7 +896,7 @@ uint32_t value;
assert(reg < 0x1ffff);
/* Write to memory mapped register. */
*(u32_t *)(e->regs + reg) = value;
*(volatile u32_t *)(e->regs + reg) = value;
}
/*===========================================================================*