[MIPS] R4000/R4400 errata workarounds
This is the gereric part of R4000/R4400 errata workarounds. They include
compiler and assembler support as well as some source code modifications
to address the problems with some combinations of multiply/divide+shift
instructions as well as the daddi and daddiu instructions.
Changes included are as follows:
1. New Kconfig options to select workarounds by platforms as necessary.
2. Arch top-level Makefile to pass necessary options to the compiler; also
incompatible configurations are detected (-mno-sym32 unsupported as
horribly intrusive for little gain).
3. Bug detection updated and shuffled -- the multiply/divide+shift problem
is lethal enough that if not worked around it makes the kernel crash in
time_init() because of a division by zero; the daddiu erratum might
also trigger early potentially, though I have not observed it. On the
other hand the daddi detection code requires the exception subsystem to
have been initialised (and is there mainly for information).
4. r4k_daddiu_bug() added so that the existence of the erratum can be
queried by code at the run time as necessary; useful for generated code
like TLB fault and copy/clear page handlers.
5. __udelay() updated as it uses multiplication in inline assembly.
Note that -mdaddi requires modified toolchain (which has been maintained
by myself and available from my site for ~4years now -- versions covered
are GCC 2.95.4 - 4.1.2 and binutils from 2.13 onwards). The -mfix-r4000
and -mfix-r4400 have been standard for a while though.
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/kernel/cpu-bugs64.c b/arch/mips/kernel/cpu-bugs64.c
index af78456..417bb3e 100644
--- a/arch/mips/kernel/cpu-bugs64.c
+++ b/arch/mips/kernel/cpu-bugs64.c
@@ -18,6 +18,15 @@
#include <asm/mipsregs.h>
#include <asm/system.h>
+static char bug64hit[] __initdata =
+ "reliable operation impossible!\n%s";
+static char nowar[] __initdata =
+ "Please report to <linux-mips@linux-mips.org>.";
+static char r4kwar[] __initdata =
+ "Enable CPU_R4000_WORKAROUNDS to rectify.";
+static char daddiwar[] __initdata =
+ "Enable CPU_DADDI_WORKAROUNDS to rectify.";
+
static inline void align_mod(const int align, const int mod)
{
asm volatile(
@@ -155,13 +164,7 @@
}
printk("no.\n");
- panic("Reliable operation impossible!\n"
-#ifndef CONFIG_CPU_R4000
- "Configure for R4000 to enable the workaround."
-#else
- "Please report to <linux-mips@linux-mips.org>."
-#endif
- );
+ panic(bug64hit, !R4000_WAR ? r4kwar : nowar);
}
static volatile int daddi_ov __initdata = 0;
@@ -233,15 +236,11 @@
}
printk("no.\n");
- panic("Reliable operation impossible!\n"
-#if !defined(CONFIG_CPU_R4000) && !defined(CONFIG_CPU_R4400)
- "Configure for R4000 or R4400 to enable the workaround."
-#else
- "Please report to <linux-mips@linux-mips.org>."
-#endif
- );
+ panic(bug64hit, !DADDI_WAR ? daddiwar : nowar);
}
+int daddiu_bug __initdata = -1;
+
static inline void check_daddiu(void)
{
long v, w, tmp;
@@ -281,7 +280,9 @@
: "=&r" (v), "=&r" (w), "=&r" (tmp)
: "I" (0xffffffffffffdb9aUL), "I" (0x1234));
- if (v == w) {
+ daddiu_bug = v != w;
+
+ if (!daddiu_bug) {
printk("no.\n");
return;
}
@@ -303,18 +304,16 @@
}
printk("no.\n");
- panic("Reliable operation impossible!\n"
-#if !defined(CONFIG_CPU_R4000) && !defined(CONFIG_CPU_R4400)
- "Configure for R4000 or R4400 to enable the workaround."
-#else
- "Please report to <linux-mips@linux-mips.org>."
-#endif
- );
+ panic(bug64hit, !DADDI_WAR ? daddiwar : nowar);
+}
+
+void __init check_bugs64_early(void)
+{
+ check_mult_sh();
+ check_daddiu();
}
void __init check_bugs64(void)
{
- check_mult_sh();
check_daddi();
- check_daddiu();
}