Re: [PATCH] [2.6.18] U4 DART improvements

Hi Olof,

Looks good.  One request:

+static inline void dart_tlb_invalidate_one(unsigned long bus_rpn)
+{
+	unsigned int reg;
+	unsigned int l, limit;
+
+	reg = DART_CNTL_U4_ENABLE | DART_CNTL_U4_IONE |
+		(bus_rpn & DART_CNTL_U4_IONE_MASK);
+	DART_OUT(DART_CNTL, reg);
+	mb();

Could you please comment the memory barriers, to say exactly _why_ a
certain barrier is needed?  I can't see why wmb() wouldn't work here,
for example (note I'm not saying it would -- I just don't see why it
wouldn't).

Same goes for every single memory barrier in the whole kernel source
code, but I have to start somewhere, heh.


Segher