From: Ralf Baechle <ralf@linux-mips.org>
To: linux-mips@linux-mips.org,
"Steven J. Hill" <Steven.Hill@imgtec.com>,
Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Subject: 74K/1074K support
Date: Wed, 25 Sep 2013 07:27:15 +0200 [thread overview]
Message-ID: <20130925052715.GB473@linux-mips.org> (raw)
Commit 006a851b10a395955c153a145ad8241494d43688 adds 74K support in c-r4k.c:
+static inline void alias_74k_erratum(struct cpuinfo_mips *c)
+{
+ /*
+ * 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.
+ */
+ if ((c->processor_id & 0xff) <= PRID_REV_ENCODE_332(2, 4, 0))
+ c->dcache.flags |= MIPS_CACHE_VTAG;
+ if ((c->processor_id & 0xff) == PRID_REV_ENCODE_332(2, 4, 0))
+ write_c0_config6(read_c0_config6() | MIPS_CONF6_SYND);
+ if (((c->processor_id & 0xff00) == PRID_IMP_1074K) &&
+ ((c->processor_id & 0xff) <= PRID_REV_ENCODE_332(1, 1, 0))) {
+ c->dcache.flags |= MIPS_CACHE_VTAG;
+ write_c0_config6(read_c0_config6() | MIPS_CONF6_SYND);
+ }
+}
But MIPS D-caches are never virtually tagged, so there is nothing in
the kernel that ever tests the MIPS_CACHE_VTAG flag in a D-cache
descriptor.
Cargo cult programming at its finest? Or was MIPS_CACHE_ALIASES what
really was meant to be set?
Ralf
next reply other threads:[~2013-09-25 5:27 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-25 5:27 Ralf Baechle [this message]
2013-09-30 21:29 ` 74K/1074K support Leonid Yegoshin
2013-09-30 21:29 ` Leonid Yegoshin
2013-10-01 12:54 ` Ralf Baechle
2013-10-01 18:06 ` Leonid Yegoshin
2013-10-01 18:06 ` Leonid Yegoshin
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