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Re: [PATCH] Fix known HW bug with MIPS core on NXP/Philips PNX8550

To: linux-mips@linux-mips.org
Subject: Re: [PATCH] Fix known HW bug with MIPS core on NXP/Philips PNX8550
From: Daniel Laird <daniel.j.laird@nxp.com>
Date: Thu, 19 Jul 2007 16:24:29 +0100
Original-recipient: rfc822;linux-mips@linux-mips.org
Sender: linux-mips-bounce@linux-mips.org
User-agent: Thunderbird 2.0.0.4 (Windows/20070604)
Update Patch

Fix known bug with MIPS core when using TLB on NXP/Philips PNX8550

Signed-off-by: Daniel Laird <daniel.j.laird@nxp.com>
---
tlb-r4k.c |    4 +++
tlbex.c | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 75 insertions(+)
---
Index: linux-2.6.22.1/arch/mips/mm/tlbex.c
===================================================================
--- linux-2.6.22.1/arch/mips/mm/tlbex.c    (revision 8)
+++ linux-2.6.22.1/arch/mips/mm/tlbex.c    (working copy)
@@ -435,6 +435,9 @@
    label_nopage_tlbm,
    label_smp_pgtable_change,
    label_r3000_write_probe_fail,
+#ifdef CONFIG_PNX8550
+    label_pnx8550_bac_reset
+#endif
};

struct label {
@@ -470,6 +473,9 @@
L_LA(_nopage_tlbm)
L_LA(_smp_pgtable_change)
L_LA(_r3000_write_probe_fail)
+#ifdef CONFIG_PNX8550
+L_LA(_pnx8550_bac_reset)
+#endif

/* convenience macros for instructions */
#ifdef CONFIG_64BIT
@@ -698,6 +704,14 @@
    r_mips_pc16(r, *p, l);
    i_bgez(p, reg, 0);
}
+#ifdef CONFIG_PNX8550
+static void il_beq(u32 **p, struct reloc **r, unsigned int reg1,
+           unsigned int reg2, enum label_id l)
+{
+    r_mips_pc16(r, *p, l);
+    i_beq(p, reg1, reg2, 0);
+}
+#endif

/* The only general purpose registers allowed in TLB handlers. */
#define K0        26
@@ -705,6 +719,7 @@

/* Some CP0 registers */
#define C0_INDEX    0, 0
+#define C0_RANDOM   1, 0
#define C0_ENTRYLO0    2, 0
#define C0_TCBIND    2, 2
#define C0_ENTRYLO1    3, 0
@@ -712,6 +727,7 @@
#define C0_BADVADDR    8, 0
#define C0_ENTRYHI    10, 0
#define C0_EPC        14, 0
+#define C0_CONFIG    16, 0
#define C0_XCONTEXT    20, 0

#ifdef CONFIG_64BIT
@@ -734,6 +750,57 @@
static __initdata struct label labels[128];
static __initdata struct reloc relocs[128];

+#ifdef CONFIG_PNX8550
+static void __init build_pnx8550_bug_fix( u32 **p, struct label **l, struct reloc **r)
+{
+#define MFC0(_reg, _cp, _sel)    \
+    ((cop0_op)  << OP_SH    \
+    | (mfc_op) << RS_SH    \
+    | (_reg)   << RT_SH    \
+    | (_cp)    << RD_SH    \
+    | (_sel))
+
+#define MTC0(_reg, _cp, _sel)    \
+    ((cop0_op)  << OP_SH    \
+    | (mtc_op) << RS_SH    \
+    | (_reg)   << RT_SH    \
+    | (_cp)    << RD_SH    \
+    | (_sel))
+
+    /* load epc and badvaddr to k0 and k1 */
+    i_MFC0(p, K0, C0_EPC);
+    i_MFC0(p, K1, C0_BADVADDR);
+
+    /* branch if code entry  */
+    il_beq(p, r, K0, K1, label_pnx8550_bac_reset);
+    i_addiu(p, K0, K0, 4);
+
+    /* branch if code entry in BDS */
+    il_beq(p, r, K0, K1, label_pnx8550_bac_reset);
+    i_nop(p);
+    /* Write data tlb entry 11..31 */
+    i_tlbwr(p);
+    i_eret(p);
+    /* BAC Reset */
+    l_pnx8550_bac_reset(l, *p);
+    **p = MFC0(K0, C0_CONFIG, 7);
+    (*p)++;
+    i_ori(p, K0, K0, (1<<14));
+
+    **p = MTC0(K0, C0_CONFIG, 7);
+    (*p)++;
+
+    /* read random reg, sub 11, div by 2 */
+    i_MFC0(p, K1, C0_RANDOM);
+    i_addiu(p, K1, K1, -11);
+    i_srl(p, K1, K1, 1);
+
+    /* use as index for tlbwi */
+    i_MTC0(p, K1, C0_INDEX);
+    i_tlbwi(p);
+}
+#endif
+
/*
 * The R3000 TLB handler is simple.
 */
@@ -1261,8 +1328,12 @@

    build_get_ptep(&p, K0, K1);
    build_update_entries(&p, K0, K1);
+#ifndef CONFIG_PNX8550
    build_tlb_write_entry(&p, &l, &r, tlb_random);
    l_leave(&l, p);
+#else
+    build_pnx8550_bug_fix(&p, &l, &r);
+#endif
    i_eret(&p); /* return from trap */

#ifdef CONFIG_64BIT
Index: linux-2.6.22.1/arch/mips/mm/tlb-r4k.c
===================================================================
--- linux-2.6.22.1/arch/mips/mm/tlb-r4k.c    (revision 8)
+++ linux-2.6.22.1/arch/mips/mm/tlb-r4k.c    (working copy)
@@ -456,7 +456,11 @@
     */
    probe_tlb(config);
    write_c0_pagemask(PM_DEFAULT_MASK);
+#ifdef CONFIG_SOC_PNX8550
+    write_c0_wired(11);
+#else
    write_c0_wired(0);
+#endif
    write_c0_framemask(0);
    temp_tlb_entry = current_cpu_data.tlbsize - 1;



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