MIPS: pm-cps: Add MIPSr6 CPU support

This patch adds support for CPUs implementing the MIPSr6 ISA to the CPS
power management code. Three changes are necessary:

1. In MIPSr6, coupled coherence is necessary when CPUS implement multiple
   Virtual Processors (VPs).

2. MIPSr6 virtual processors are more like real cores and cannot yield
   to other VPs on the same core, so drop the MT ASE yield instruction.

3. To halt a MIPSr6 VP, the CPC VP_STOP register is used rather than the
   MT ASE TCHalt CP0 register.

Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
Reviewed-by: Paul Burton <paul.burton@imgtec.com>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14225/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/pm-cps.h

@@ -13,10 +13,12 @@
 
 /*
  * The CM & CPC can only handle coherence & power control on a per-core basis,
- * thus in an MT system the VPEs within each core are coupled and can only
+ * thus in an MT system the VP(E)s within each core are coupled and can only
  * enter or exit states requiring CM or CPC assistance in unison.
  */
-#ifdef CONFIG_MIPS_MT
+#if defined(CONFIG_CPU_MIPSR6)
+# define coupled_coherence cpu_has_vp
+#elif defined(CONFIG_MIPS_MT)
 # define coupled_coherence cpu_has_mipsmt
 #else
 # define coupled_coherence 0

arch/mips/kernel/pm-cps.c

@@ -129,7 +129,7 @@ int cps_pm_enter_state(enum cps_pm_state state)
 		return -EINVAL;
 
 	/* Calculate which coupled CPUs (VPEs) are online */
-#ifdef CONFIG_MIPS_MT
+#if defined(CONFIG_MIPS_MT) || defined(CONFIG_CPU_MIPSR6)
 	if (cpu_online(cpu)) {
 		cpumask_and(coupled_mask, cpu_online_mask,
 			    &cpu_sibling_map[cpu]);
@@ -431,7 +431,8 @@ static void * __init cps_gen_entry_code(unsigned cpu, enum cps_pm_state state)
 			uasm_i_lw(&p, t0, 0, r_nc_count);
 			uasm_il_bltz(&p, &r, t0, lbl_secondary_cont);
 			uasm_i_ehb(&p);
-			uasm_i_yield(&p, zero, t1);
+			if (cpu_has_mipsmt)
+				uasm_i_yield(&p, zero, t1);
 			uasm_il_b(&p, &r, lbl_poll_cont);
 			uasm_i_nop(&p);
 		} else {
@@ -439,8 +440,21 @@ static void * __init cps_gen_entry_code(unsigned cpu, enum cps_pm_state state)
 			 * The core will lose power & this VPE will not continue
 			 * so it can simply halt here.
 			 */
-			uasm_i_addiu(&p, t0, zero, TCHALT_H);
-			uasm_i_mtc0(&p, t0, 2, 4);
+			if (cpu_has_mipsmt) {
+				/* Halt the VPE via C0 tchalt register */
+				uasm_i_addiu(&p, t0, zero, TCHALT_H);
+				uasm_i_mtc0(&p, t0, 2, 4);
+			} else if (cpu_has_vp) {
+				/* Halt the VP via the CPC VP_STOP register */
+				unsigned int vpe_id;
+
+				vpe_id = cpu_vpe_id(&cpu_data[cpu]);
+				uasm_i_addiu(&p, t0, zero, 1 << vpe_id);
+				UASM_i_LA(&p, t1, (long)addr_cpc_cl_vp_stop());
+				uasm_i_sw(&p, t0, 0, t1);
+			} else {
+				BUG();
+			}
 			uasm_build_label(&l, p, lbl_secondary_hang);
 			uasm_il_b(&p, &r, lbl_secondary_hang);
 			uasm_i_nop(&p);