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authorMaciej W. Rozycki <macro@codesourcery.com>2014-11-16 01:02:29 +0000
committerRalf Baechle <ralf@linux-mips.org>2015-04-02 13:54:18 +0200
commite2e7f29af84aa59dd8191b9f6fee80aafa4e06cd (patch)
treed24402478d2956b93d2d881673d527f0a483eb11 /arch/mips/mm/c-r4k.c
parent12a8471de9e8dc3c867e15bbf4a37152d2f690b8 (diff)
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MIPS: c-r4k.c: Fix the 74K D-cache alias erratum workaround
Fix the 74K D-cache alias erratum workaround so that it actually works. Our current code sets MIPS_CACHE_VTAG for the D-cache, but that flag only has any effect for the I-cache. Additionally MIPS_CACHE_PINDEX is set for the D-cache if CP0.Config7.AR is also set for an affected processor, leading to confusing information in the bootstrap log (the flag isn't used beyond that). So delete the setting of MIPS_CACHE_VTAG and rely on MIPS_CACHE_ALIASES, set in a common place, removing I-cache coherency issues seen in GDB testing with software breakpoints, gdbserver and ptrace(2), on affected systems. While at it add a little piece of explanation of what CP0.Config6.SYND is so that people do not have to chase documentation. Signed-off-by: Maciej W. Rozycki <macro@codesourcery.com> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/8507/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/mm/c-r4k.c')
-rw-r--r--arch/mips/mm/c-r4k.c23
1 files changed, 15 insertions, 8 deletions
diff --git a/arch/mips/mm/c-r4k.c b/arch/mips/mm/c-r4k.c
index 58e2eeddc391..0dbb65a51ce5 100644
--- a/arch/mips/mm/c-r4k.c
+++ b/arch/mips/mm/c-r4k.c
@@ -889,33 +889,39 @@ static inline void rm7k_erratum31(void)
}
}
-static inline void alias_74k_erratum(struct cpuinfo_mips *c)
+static inline int alias_74k_erratum(struct cpuinfo_mips *c)
{
unsigned int imp = c->processor_id & PRID_IMP_MASK;
unsigned int rev = c->processor_id & PRID_REV_MASK;
+ int present = 0;
/*
* Early versions of the 74K do not update the cache tags on a
* vtag miss/ptag hit which can occur in the case of KSEG0/KUSEG
- * aliases. In this case it is better to treat the cache as always
- * having aliases.
+ * aliases. In this case it is better to treat the cache as always
+ * having aliases. Also disable the synonym tag update feature
+ * where available. In this case no opportunistic tag update will
+ * happen where a load causes a virtual address miss but a physical
+ * address hit during a D-cache look-up.
*/
switch (imp) {
case PRID_IMP_74K:
if (rev <= PRID_REV_ENCODE_332(2, 4, 0))
- c->dcache.flags |= MIPS_CACHE_VTAG;
+ present = 1;
if (rev == PRID_REV_ENCODE_332(2, 4, 0))
write_c0_config6(read_c0_config6() | MIPS_CONF6_SYND);
break;
case PRID_IMP_1074K:
if (rev <= PRID_REV_ENCODE_332(1, 1, 0)) {
- c->dcache.flags |= MIPS_CACHE_VTAG;
+ present = 1;
write_c0_config6(read_c0_config6() | MIPS_CONF6_SYND);
}
break;
default:
BUG();
}
+
+ return present;
}
static void b5k_instruction_hazard(void)
@@ -939,6 +945,7 @@ static void probe_pcache(void)
struct cpuinfo_mips *c = &current_cpu_data;
unsigned int config = read_c0_config();
unsigned int prid = read_c0_prid();
+ int has_74k_erratum = 0;
unsigned long config1;
unsigned int lsize;
@@ -1247,7 +1254,7 @@ static void probe_pcache(void)
case CPU_74K:
case CPU_1074K:
- alias_74k_erratum(c);
+ has_74k_erratum = alias_74k_erratum(c);
/* Fall through. */
case CPU_M14KC:
case CPU_M14KEC:
@@ -1262,7 +1269,7 @@ static void probe_pcache(void)
if (!(read_c0_config7() & MIPS_CONF7_IAR) &&
(c->icache.waysize > PAGE_SIZE))
c->icache.flags |= MIPS_CACHE_ALIASES;
- if (read_c0_config7() & MIPS_CONF7_AR) {
+ if (!has_74k_erratum && (read_c0_config7() & MIPS_CONF7_AR)) {
/*
* Effectively physically indexed dcache,
* thus no virtual aliases.
@@ -1271,7 +1278,7 @@ static void probe_pcache(void)
break;
}
default:
- if (c->dcache.waysize > PAGE_SIZE)
+ if (has_74k_erratum || c->dcache.waysize > PAGE_SIZE)
c->dcache.flags |= MIPS_CACHE_ALIASES;
}