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>

2 files changed, 27 insertions, 15 deletions

diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index c6568bf4b1b0..265c97da6619 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/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
diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index afeef93f81a7..c052df8ae7d7 100644
--- a/arch/mips/mm/tlbex.c
+++ b/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");