Performance bug in c-r4k.c cache handling code

[Thiemo Seufer <ths@networkno.de>]

Hello All,

I found an performance bug in c-r4k.c:r4k_dma_cache_inv, where a
Hit_Writeback_Inv instead of Hit_Invalidate is done. Ralf mentioned
this is probably due to broken Hit_Invalidate cache ops on some
CPUs, does anybody have more information about this? The appended
patch works apparently fine on R4400, R4600v2.0, R5000.


Thiemo


Index: arch/mips/mm/c-r4k.c
===================================================================
RCS file: /home/cvs/linux/arch/mips/mm/c-r4k.c,v
retrieving revision 1.119
diff -u -p -r1.119 c-r4k.c
--- arch/mips/mm/c-r4k.c	9 Sep 2005 20:26:54 -0000	1.119
+++ arch/mips/mm/c-r4k.c	19 Sep 2005 15:33:35 -0000
@@ -685,7 +685,7 @@ static void r4k_dma_cache_inv(unsigned l
 		a = addr & ~(sc_lsize - 1);
 		end = (addr + size - 1) & ~(sc_lsize - 1);
 		while (1) {
-			flush_scache_line(a);	/* Hit_Writeback_Inv_SD */
+			invalidate_scache_line(a);	/* Hit_Invalidate_SD */
 			if (a == end)
 				break;
 			a += sc_lsize;
@@ -702,7 +702,7 @@ static void r4k_dma_cache_inv(unsigned l
 		a = addr & ~(dc_lsize - 1);
 		end = (addr + size - 1) & ~(dc_lsize - 1);
 		while (1) {
-			flush_dcache_line(a);	/* Hit_Writeback_Inv_D */
+			invalidate_dcache_line(a);	/* Hit_Invalidate_D */
 			if (a == end)
 				break;
 			a += dc_lsize;