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Re: [PATCH] MIPS: micromips: Fix improper definition of ISA exception bi

To: "Steven J. Hill" <Steven.Hill@imgtec.com>
Subject: Re: [PATCH] MIPS: micromips: Fix improper definition of ISA exception bit.
From: David Daney <ddaney.cavm@gmail.com>
Date: Tue, 04 Jun 2013 11:42:48 -0700
Cc: linux-mips@linux-mips.org, ralf@linux-mips.org
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On 06/04/2013 11:22 AM, Steven J. Hill wrote:
The ISA exception bit selects whether exceptions are taken in classic
MIPS or microMIPS mode. This bit is Config3.ISAOnExc and is bit 16. It
It was improperly defined as bits 16 and 17. Fortunately, bit 17 is
read-only and did not effect microMIPS operation. However, detecting
a classic or microMIPS kernel when examining the /proc/cpuinfo file,
the result always showed a microMIPS kernel.

Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>
---
  arch/mips/include/asm/mipsregs.h |    2 +-
  arch/mips/kernel/cpu-probe.c     |   11 ++++++-----
  2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h
index 87e6207..fed1c3e 100644
--- a/arch/mips/include/asm/mipsregs.h
+++ b/arch/mips/include/asm/mipsregs.h
@@ -596,7 +596,7 @@
  #define MIPS_CONF3_RXI                (_ULCAST_(1) << 12)
  #define MIPS_CONF3_ULRI               (_ULCAST_(1) << 13)
  #define MIPS_CONF3_ISA                (_ULCAST_(3) << 14)
-#define MIPS_CONF3_ISA_OE      (_ULCAST_(3) << 16)
+#define MIPS_CONF3_ISA_OE      (_ULCAST_(1) << 16)
  #define MIPS_CONF3_VZ         (_ULCAST_(1) << 23)

  #define MIPS_CONF4_MMUSIZEEXT (_ULCAST_(255) << 0)
diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index c6568bf..822bfe4 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -256,6 +256,12 @@ static inline unsigned int decode_config3(struct 
cpuinfo_mips *c)
                c->ases |= MIPS_ASE_SMARTMIPS;
                c->options |= MIPS_CPU_RIXI;
        }
+       if (config3 & MIPS_CONF3_ISA) {
+               c->options |= MIPS_CPU_MICROMIPS;
+#ifdef CONFIG_CPU_MICROMIPS
+               write_c0_config3(config3 | MIPS_CONF3_ISA_OE);
+#endif
+       }

This function is supposed to be decoding the bits in config3, it shouldn't be changing the CPU operating mode.

Please move this to some other place (like prom_init() or kernel_entry_setup).


        if (config3 & MIPS_CONF3_RXI)
                c->options |= MIPS_CPU_RIXI;
        if (config3 & MIPS_CONF3_DSP)
@@ -270,11 +276,6 @@ static inline unsigned int decode_config3(struct 
cpuinfo_mips *c)
                c->ases |= MIPS_ASE_MIPSMT;
        if (config3 & MIPS_CONF3_ULRI)
                c->options |= MIPS_CPU_ULRI;
-       if (config3 & MIPS_CONF3_ISA)
-               c->options |= MIPS_CPU_MICROMIPS;
-#ifdef CONFIG_CPU_MICROMIPS
-       write_c0_config3(read_c0_config3() | MIPS_CONF3_ISA_OE);
-#endif
        if (config3 & MIPS_CONF3_VZ)
                c->ases |= MIPS_ASE_VZ;




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