Re: [linux-fbdev] Re: readl() and friends and eieio on PPC

On 14 Aug 1999, Jes Sorensen wrote:

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"David" == David A Gatwood [off-list ref] writes:

David> On Fri, 13 Aug 1999, Paul Mackerras wrote:

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Surely it should only take a couple of cycles to move a register to
another and clear it?  I agree it's a pain though.  Actually, with
gcc the asm statement that uses the eieio could just specify the
register (which one is it?) as an input and give it the value 0.

David> For some reason, just loading the value isn't enough.  The code
David> that Gilbert put in as a workaround shortly before DR3 looks
David> like this:

David> #define eieio() __asm__ volatile("li 0,0: cmpwi 0,0; bne+ 0f;
David> eieio; 0:" : : : "0")

Defininf a C function with the name of a PPC specific assembler
function is pretty stupid. To the best of my knowledge wmb() is the

Well, David was talking about replacing the eieio() macro (which Linux/PPC had
since ages) by something that works around bugs in the hardware.

generic name for the thing you are looking for.

Time to start grepping in include/asm-alpha/system.h. Huh, Alpha AXP has no
`rmb' mnemonic ;-)

Greetings,

						Geert

--
Geert Uytterhoeven                     Geert.Uytterhoeven@cs.kuleuven.ac.be
Wavelets, Linux/{m68k~Amiga,PPC~CHRP}  http://www.cs.kuleuven.ac.be/~geert/
Department of Computer Science -- Katholieke Universiteit Leuven -- Belgium



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