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Re: [PATCH 4/6] MIPS: mm: Use the TLBINVF instruction to flush the VTLB

To: Markos Chandras <markos.chandras@imgtec.com>
Subject: Re: [PATCH 4/6] MIPS: mm: Use the TLBINVF instruction to flush the VTLB
From: David Daney <ddaney.cavm@gmail.com>
Date: Mon, 11 Nov 2013 12:10:25 -0800
Cc: linux-mips@linux-mips.org, Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
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On 11/07/2013 09:08 AM, Markos Chandras wrote:
From: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>

The TLBINVF instruction can be used to flush the entire VTLB.
This eliminates the need for the TLBWI loop and improves performance.

Reviewed-by: Paul Burton <paul.burton@imgtec.com>
Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>


This should be split into two patches.  One for each file.

Also...

---
  arch/mips/include/asm/mipsregs.h | 13 +++++++++++++
  arch/mips/mm/tlb-r4k.c           | 18 ++++++++++++------
  2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h
index 412fe99..9cd0e13 100644
--- a/arch/mips/include/asm/mipsregs.h
+++ b/arch/mips/include/asm/mipsregs.h
@@ -685,6 +685,19 @@ static inline int mm_insn_16bit(u16 insn)
  }

  /*
+ * TLB Invalidate Flush
+ */
+static inline void tlbinvf(void)
+{
+       __asm__ __volatile__(
+               ".set push\n\t"
+               ".set noreorder\n\t"

... Why do you need noreorder here?

+               ".word 0x42000004\n\t" /* tlbinvf */
+               ".set pop");
+}
+
+
+/*
   * Functions to access the R10000 performance counters.        These are 
basically
   * mfc0 and mtc0 instructions from and to coprocessor register with a 5-bit
   * performance counter number encoded into bits 1 ... 5 of the instruction.
diff --git a/arch/mips/mm/tlb-r4k.c b/arch/mips/mm/tlb-r4k.c
index 363aa03..427dcac 100644
--- a/arch/mips/mm/tlb-r4k.c
+++ b/arch/mips/mm/tlb-r4k.c
@@ -83,13 +83,19 @@ void local_flush_tlb_all(void)
        entry = read_c0_wired();

        /* Blast 'em all away. */
-       while (entry < current_cpu_data.tlbsize) {
-               /* Make sure all entries differ. */
-               write_c0_entryhi(UNIQUE_ENTRYHI(entry));
-               write_c0_index(entry);
+       if (cpu_has_tlbinv && current_cpu_data.tlbsize) {
+               write_c0_index(0);
                mtc0_tlbw_hazard();
-               tlb_write_indexed();
-               entry++;
+               tlbinvf();  /* invalidate VTLB */
+       } else {
+               while (entry < current_cpu_data.tlbsize) {
+                       /* Make sure all entries differ. */
+                       write_c0_entryhi(UNIQUE_ENTRYHI(entry));
+                       write_c0_index(entry);
+                       mtc0_tlbw_hazard();
+                       tlb_write_indexed();
+                       entry++;
+               }
        }
        tlbw_use_hazard();
        write_c0_entryhi(old_ctx);



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