MIPS: Allow platform specific scratch registers

XLR/XLP COP0 scratch is register 22, sel 0-7. Add a function
c0_kscratch() which returns the scratch register for the platform,
and use the return value while generating TLB handlers.

Setup kscratch_mask to 0xf for XLR/XLP since the config4 register
does not exist. This allows the kernel to allocate scratch registers
0-3 if needed.

Signed-off-by: Jayachandran C <jchandra@broadcom.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5445/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/cpu-probe.c

@@ -959,6 +959,7 @@ static inline void cpu_probe_netlogic(struct cpuinfo_mips *c, int cpu)
 		set_isa(c, MIPS_CPU_ISA_M64R1);
 		c->tlbsize = ((read_c0_config1() >> 25) & 0x3f) + 1;
 	}
+	c->kscratch_mask = 0xf;
 }
 
 #ifdef CONFIG_64BIT

arch/mips/mm/tlbex.c

@@ -305,6 +305,17 @@ static int check_for_high_segbits __cpuinitdata;
 
 static unsigned int kscratch_used_mask __cpuinitdata;
 
+static inline int __maybe_unused c0_kscratch(void)
+{
+	switch (current_cpu_type()) {
+	case CPU_XLP:
+	case CPU_XLR:
+		return 22;
+	default:
+		return 31;
+	}
+}
+
 static int __cpuinit allocate_kscratch(void)
 {
 	int r;
@@ -336,7 +347,7 @@ static struct work_registers __cpuinit build_get_work_registers(u32 **p)
 
 	if (scratch_reg > 0) {
 		/* Save in CPU local C0_KScratch? */
-		UASM_i_MTC0(p, 1, 31, scratch_reg);
+		UASM_i_MTC0(p, 1, c0_kscratch(), scratch_reg);
 		r.r1 = K0;
 		r.r2 = K1;
 		r.r3 = 1;
@@ -385,7 +396,7 @@ static struct work_registers __cpuinit build_get_work_registers(u32 **p)
 static void __cpuinit build_restore_work_registers(u32 **p)
 {
 	if (scratch_reg > 0) {
-		UASM_i_MFC0(p, 1, 31, scratch_reg);
+		UASM_i_MFC0(p, 1, c0_kscratch(), scratch_reg);
 		return;
 	}
 	/* K0 already points to save area, restore $1 and $2  */
@@ -674,7 +685,7 @@ static __cpuinit void build_restore_pagemask(u32 **p,
 			uasm_il_b(p, r, lid);
 		}
 		if (scratch_reg > 0)
-			UASM_i_MFC0(p, 1, 31, scratch_reg);
+			UASM_i_MFC0(p, 1, c0_kscratch(), scratch_reg);
 		else
 			UASM_i_LW(p, 1, scratchpad_offset(0), 0);
 	} else {
@@ -817,7 +828,7 @@ build_get_pmde64(u32 **p, struct uasm_label **l, struct uasm_reloc **r,
 #ifdef CONFIG_MIPS_PGD_C0_CONTEXT
 	if (pgd_reg != -1) {
 		/* pgd is in pgd_reg */
-		UASM_i_MFC0(p, ptr, 31, pgd_reg);
+		UASM_i_MFC0(p, ptr, c0_kscratch(), pgd_reg);
 	} else {
 		/*
 		 * &pgd << 11 stored in CONTEXT [23..63].
@@ -930,7 +941,7 @@ build_get_pgd_vmalloc64(u32 **p, struct uasm_label **l, struct uasm_reloc **r,
 
 		if (mode == refill_scratch) {
 			if (scratch_reg > 0)
-				UASM_i_MFC0(p, 1, 31, scratch_reg);
+				UASM_i_MFC0(p, 1, c0_kscratch(), scratch_reg);
 			else
 				UASM_i_LW(p, 1, scratchpad_offset(0), 0);
 		} else {
@@ -1096,7 +1107,7 @@ struct mips_huge_tlb_info {
 static struct mips_huge_tlb_info __cpuinit
 build_fast_tlb_refill_handler (u32 **p, struct uasm_label **l,
 			       struct uasm_reloc **r, unsigned int tmp,
-			       unsigned int ptr, int c0_scratch)
+			       unsigned int ptr, int c0_scratch_reg)
 {
 	struct mips_huge_tlb_info rv;
 	unsigned int even, odd;
@@ -1110,12 +1121,12 @@ build_fast_tlb_refill_handler (u32 **p, struct uasm_label **l,
 		UASM_i_MFC0(p, tmp, C0_BADVADDR);
 
 		if (pgd_reg != -1)
-			UASM_i_MFC0(p, ptr, 31, pgd_reg);
+			UASM_i_MFC0(p, ptr, c0_kscratch(), pgd_reg);
 		else
 			UASM_i_MFC0(p, ptr, C0_CONTEXT);
 
-		if (c0_scratch >= 0)
-			UASM_i_MTC0(p, scratch, 31, c0_scratch);
+		if (c0_scratch_reg >= 0)
+			UASM_i_MTC0(p, scratch, c0_kscratch(), c0_scratch_reg);
 		else
 			UASM_i_SW(p, scratch, scratchpad_offset(0), 0);
 
@@ -1130,14 +1141,14 @@ build_fast_tlb_refill_handler (u32 **p, struct uasm_label **l,
 		}
 	} else {
 		if (pgd_reg != -1)
-			UASM_i_MFC0(p, ptr, 31, pgd_reg);
+			UASM_i_MFC0(p, ptr, c0_kscratch(), pgd_reg);
 		else
 			UASM_i_MFC0(p, ptr, C0_CONTEXT);
 
 		UASM_i_MFC0(p, tmp, C0_BADVADDR);
 
-		if (c0_scratch >= 0)
-			UASM_i_MTC0(p, scratch, 31, c0_scratch);
+		if (c0_scratch_reg >= 0)
+			UASM_i_MTC0(p, scratch, c0_kscratch(), c0_scratch_reg);
 		else
 			UASM_i_SW(p, scratch, scratchpad_offset(0), 0);
 
@@ -1242,8 +1253,8 @@ build_fast_tlb_refill_handler (u32 **p, struct uasm_label **l,
 	}
 	UASM_i_MTC0(p, odd, C0_ENTRYLO1); /* load it */
 
-	if (c0_scratch >= 0) {
-		UASM_i_MFC0(p, scratch, 31, c0_scratch);
+	if (c0_scratch_reg >= 0) {
+		UASM_i_MFC0(p, scratch, c0_kscratch(), c0_scratch_reg);
 		build_tlb_write_entry(p, l, r, tlb_random);
 		uasm_l_leave(l, *p);
 		rv.restore_scratch = 1;
@@ -1490,7 +1501,7 @@ static void __cpuinit build_r4000_setup_pgd(void)
 	} else {
 		/* PGD in c0_KScratch */
 		uasm_i_jr(&p, 31);
-		UASM_i_MTC0(&p, a0, 31, pgd_reg);
+		UASM_i_MTC0(&p, a0, c0_kscratch(), pgd_reg);
 	}
 	if (p - tlbmiss_handler_setup_pgd_array > ARRAY_SIZE(tlbmiss_handler_setup_pgd_array))
 		panic("tlbmiss_handler_setup_pgd_array space exceeded");