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Re: [PATCH] MIPS: mm: c-r4k: Detect instruction cache aliases

To: Markos Chandras <>,
Subject: Re: [PATCH] MIPS: mm: c-r4k: Detect instruction cache aliases
From: Sergei Shtylyov <>
Date: Wed, 29 Jan 2014 21:10:12 +0300
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On 01/29/2014 04:41 PM, Markos Chandras wrote:

The *Aptiv cores can use the CONF7/IAR bit to detect if the core
has hardware support to remove instruction cache aliasing.

Signed-off-by: Markos Chandras <>
This patch is for the upstream-sfr/mips-for-linux-next tree

diff --git a/arch/mips/mm/c-r4k.c b/arch/mips/mm/c-r4k.c
index 13b549a..e790524 100644
--- a/arch/mips/mm/c-r4k.c
+++ b/arch/mips/mm/c-r4k.c
@@ -1110,7 +1110,10 @@ static void probe_pcache(void)
      case CPU_PROAPTIV:
          if (current_cpu_type() == CPU_74K)
-        if ((read_c0_config7() & (1 << 16))) {
+        if (!(read_c0_config7() & MIPS_CONF7_IAR))
+            if (c->icache.waysize > PAGE_SIZE)

    Why not fold these to a single *if*?

I suppose I could do that. Thanks

+                c->icache.flags |= MIPS_CACHE_ALIASES;
+        if (read_c0_config7() & MIPS_CONF7_AR) {

    You didn't document this change. Ideally, it should be in a separate

Nothing has changed. Instead of using the '16' magic value, I just documented
that bit along with the IAR one.

   You should have noted that in the changelog, at least.

WBR, Sergei

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