MIPS: Add support for FTLBs

The Fixed Page Size TLB (FTLB) is a set-associative dual entry TLB. Its
purpose is to reduce the number of TLB misses by increasing the effective
TLB size and keep the implementation complexity to minimum levels.
A supported core can have both VTLB and FTLB.

Reviewed-by: James Hogan <james.hogan@imgtec.com>
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>
Signed-off-by: John Crispin <blogic@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/6139/

3 files changed, 103 insertions, 7 deletions

diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index f86414e..65b61bb 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -163,6 +163,25 @@ static void set_isa(struct cpuinfo_mips *c, unsigned int isa)
 static char unknown_isa[] = KERN_ERR \
 	"Unsupported ISA type, c0.config0: %d.";
 
+static void set_ftlb_enable(struct cpuinfo_mips *c, int enable)
+{
+	unsigned int config6;
+	/*
+	 * Config6 is implementation dependent and it's currently only
+	 * used by proAptiv
+	 */
+	if (c->cputype == CPU_PROAPTIV) {
+		config6 = read_c0_config6();
+		if (enable)
+			/* Enable FTLB */
+			write_c0_config6(config6 | MIPS_CONF6_FTLBEN);
+		else
+			/* Disable FTLB */
+			write_c0_config6(config6 &  ~MIPS_CONF6_FTLBEN);
+		back_to_back_c0_hazard();
+	}
+}
+
 static inline unsigned int decode_config0(struct cpuinfo_mips *c)
 {
 	unsigned int config0;
@@ -170,8 +189,13 @@ static inline unsigned int decode_config0(struct cpuinfo_mips *c)
 
 	config0 = read_c0_config();
 
-	if (((config0 & MIPS_CONF_MT) >> 7) == 1)
+	/*
+	 * Look for Standard TLB or Dual VTLB and FTLB
+	 */
+	if ((((config0 & MIPS_CONF_MT) >> 7) == 1) ||
+	    (((config0 & MIPS_CONF_MT) >> 7) == 4))
 		c->options |= MIPS_CPU_TLB;
+
 	isa = (config0 & MIPS_CONF_AT) >> 13;
 	switch (isa) {
 	case 0:
@@ -226,8 +250,11 @@ static inline unsigned int decode_config1(struct cpuinfo_mips *c)
 		c->options |= MIPS_CPU_FPU;
 		c->options |= MIPS_CPU_32FPR;
 	}
-	if (cpu_has_tlb)
+	if (cpu_has_tlb) {
 		c->tlbsize = ((config1 & MIPS_CONF1_TLBS) >> 25) + 1;
+		c->tlbsizevtlb = c->tlbsize;
+		c->tlbsizeftlbsets = 0;
+	}
 
 	return config1 & MIPS_CONF_M;
 }
@@ -281,16 +308,50 @@ static inline unsigned int decode_config3(struct cpuinfo_mips *c)
 static inline unsigned int decode_config4(struct cpuinfo_mips *c)
 {
 	unsigned int config4;
+	unsigned int newcf4;
+	unsigned int mmuextdef;
+	unsigned int ftlb_page = MIPS_CONF4_FTLBPAGESIZE;
 
 	config4 = read_c0_config4();
 
-	if ((config4 & MIPS_CONF4_MMUEXTDEF) == MIPS_CONF4_MMUEXTDEF_MMUSIZEEXT
-	    && cpu_has_tlb)
-		c->tlbsize += (config4 & MIPS_CONF4_MMUSIZEEXT) * 0x40;
-
 	if (cpu_has_tlb) {
 		if (((config4 & MIPS_CONF4_IE) >> 29) == 2)
 			c->options |= MIPS_CPU_TLBINV;
+		mmuextdef = config4 & MIPS_CONF4_MMUEXTDEF;
+		switch (mmuextdef) {
+		case MIPS_CONF4_MMUEXTDEF_MMUSIZEEXT:
+			c->tlbsize += (config4 & MIPS_CONF4_MMUSIZEEXT) * 0x40;
+			c->tlbsizevtlb = c->tlbsize;
+			break;
+		case MIPS_CONF4_MMUEXTDEF_VTLBSIZEEXT:
+			c->tlbsizevtlb +=
+				((config4 & MIPS_CONF4_VTLBSIZEEXT) >>
+				  MIPS_CONF4_VTLBSIZEEXT_SHIFT) * 0x40;
+			c->tlbsize = c->tlbsizevtlb;
+			ftlb_page = MIPS_CONF4_VFTLBPAGESIZE;
+			/* fall through */
+		case MIPS_CONF4_MMUEXTDEF_FTLBSIZEEXT:
+			newcf4 = (config4 & ~ftlb_page) |
+				(page_size_ftlb(mmuextdef) <<
+				 MIPS_CONF4_FTLBPAGESIZE_SHIFT);
+			write_c0_config4(newcf4);
+			back_to_back_c0_hazard();
+			config4 = read_c0_config4();
+			if (config4 != newcf4) {
+				pr_err("PAGE_SIZE 0x%lx is not supported by FTLB (config4=0x%x)\n",
+				       PAGE_SIZE, config4);
+				/* Switch FTLB off */
+				set_ftlb_enable(c, 0);
+				break;
+			}
+			c->tlbsizeftlbsets = 1 <<
+				((config4 & MIPS_CONF4_FTLBSETS) >>
+				 MIPS_CONF4_FTLBSETS_SHIFT);
+			c->tlbsizeftlbways = ((config4 & MIPS_CONF4_FTLBWAYS) >>
+					      MIPS_CONF4_FTLBWAYS_SHIFT) + 2;
+			c->tlbsize += c->tlbsizeftlbways * c->tlbsizeftlbsets;
+			break;
+		}
 	}
 
 	c->kscratch_mask = (config4 >> 16) & 0xff;
@@ -319,6 +380,9 @@ static void decode_configs(struct cpuinfo_mips *c)
 
 	c->scache.flags = MIPS_CACHE_NOT_PRESENT;
 
+	/* Enable FTLB if present */
+	set_ftlb_enable(c, 1);
+
 	ok = decode_config0(c);			/* Read Config registers.  */
 	BUG_ON(!ok);				/* Arch spec violation!	 */
 	if (ok)
@@ -682,7 +746,6 @@ static inline void cpu_probe_legacy(struct cpuinfo_mips *c, unsigned int cpu)
 
 static inline void cpu_probe_mips(struct cpuinfo_mips *c, unsigned int cpu)
 {
-	decode_configs(c);
 	switch (c->processor_id & PRID_IMP_MASK) {
 	case PRID_IMP_4KC:
 		c->cputype = CPU_4KC;
@@ -756,6 +819,8 @@ static inline void cpu_probe_mips(struct cpuinfo_mips *c, unsigned int cpu)
 		break;
 	}
 
+	decode_configs(c);
+
 	spram_config();
 }
 
diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S
index 47d7583..d84f6a5 100644
--- a/arch/mips/kernel/genex.S
+++ b/arch/mips/kernel/genex.S
@@ -476,6 +476,7 @@ NESTED(nmi_handler, PT_SIZE, sp)
 	BUILD_HANDLER ov ov sti silent			/* #12 */
 	BUILD_HANDLER tr tr sti silent			/* #13 */
 	BUILD_HANDLER fpe fpe fpe silent		/* #15 */
+	BUILD_HANDLER ftlb ftlb none silent		/* #16 */
 	BUILD_HANDLER mdmx mdmx sti silent		/* #22 */
 #ifdef	CONFIG_HARDWARE_WATCHPOINTS
 	/*
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index e98f3ab..39370e1 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -78,6 +78,7 @@ extern asmlinkage void handle_cpu(void);
 extern asmlinkage void handle_ov(void);
 extern asmlinkage void handle_tr(void);
 extern asmlinkage void handle_fpe(void);
+extern asmlinkage void handle_ftlb(void);
 extern asmlinkage void handle_mdmx(void);
 extern asmlinkage void handle_watch(void);
 extern asmlinkage void handle_mt(void);
@@ -1460,6 +1461,34 @@ asmlinkage void cache_parity_error(void)
 	panic("Can't handle the cache error!");
 }
 
+asmlinkage void do_ftlb(void)
+{
+	const int field = 2 * sizeof(unsigned long);
+	unsigned int reg_val;
+
+	/* For the moment, report the problem and hang. */
+	if (cpu_has_mips_r2 &&
+	    ((current_cpu_data.processor_id && 0xff0000) == PRID_COMP_MIPS)) {
+		pr_err("FTLB error exception, cp0_ecc=0x%08x:\n",
+		       read_c0_ecc());
+		pr_err("cp0_errorepc == %0*lx\n", field, read_c0_errorepc());
+		reg_val = read_c0_cacheerr();
+		pr_err("c0_cacheerr == %08x\n", reg_val);
+
+		if ((reg_val & 0xc0000000) == 0xc0000000) {
+			pr_err("Decoded c0_cacheerr: FTLB parity error\n");
+		} else {
+			pr_err("Decoded c0_cacheerr: %s cache fault in %s reference.\n",
+			       reg_val & (1<<30) ? "secondary" : "primary",
+			       reg_val & (1<<31) ? "data" : "insn");
+		}
+	} else {
+		pr_err("FTLB error exception\n");
+	}
+	/* Just print the cacheerr bits for now */
+	cache_parity_error();
+}
+
 /*
  * SDBBP EJTAG debug exception handler.
  * We skip the instruction and return to the next instruction.
@@ -2009,6 +2038,7 @@ void __init trap_init(void)
 	if (cpu_has_fpu && !cpu_has_nofpuex)
 		set_except_vector(15, handle_fpe);
 
+	set_except_vector(16, handle_ftlb);
 	set_except_vector(22, handle_mdmx);
 
 	if (cpu_has_mcheck)