LoongArch: Save and restore CSR.CNTC for hibernation

commit ceb9155d058a11242aa0572875c44e9713b1a2be upstream.

Save and restore CSR.CNTC for hibernation which is similar to suspend.

For host this is unnecessary because sched clock is ensured continuous,
but for kvm guest sched clock isn't enough because rdtime.d should also
be continuous.

Host::rdtime.d = Host::CSR.CNTC + counter
Guest::rdtime.d = Host::CSR.CNTC + Host::CSR.GCNTC + Guest::CSR.CNTC + counter

so,

Guest::rdtime.d = Host::rdtime.d + Host::CSR.GCNTC + Guest::CSR.CNTC

To ensure Guest::rdtime.d continuous, Host::rdtime.d should be at first
continuous, while Host::CSR.GCNTC / Guest::CSR.CNTC is maintained by KVM.

Cc: [email protected]
Signed-off-by: Xianglai Li <[email protected]>
Signed-off-by: Huacai Chen <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
(cherry picked from commit 2135336574354e1de870015e2b39b5b793f131cb)
Signed-off-by: Jack Vogel <[email protected]>

Author: chenhuacai

arch/loongarch/kernel/time.c

@@ -111,7 +111,7 @@ static unsigned long __init get_loops_per_jiffy(void)
 	return lpj;
 }
 
-static long init_offset __nosavedata;
+static long init_offset;
 
 void save_counter(void)
 {

arch/loongarch/power/hibernate.c

@@ -2,6 +2,7 @@
 #include <asm/fpu.h>
 #include <asm/loongson.h>
 #include <asm/sections.h>
+#include <asm/time.h>
 #include <asm/tlbflush.h>
 #include <linux/suspend.h>
 
@@ -14,6 +15,7 @@ struct pt_regs saved_regs;
 
 void save_processor_state(void)
 {
+	save_counter();
 	saved_crmd = csr_read32(LOONGARCH_CSR_CRMD);
 	saved_prmd = csr_read32(LOONGARCH_CSR_PRMD);
 	saved_euen = csr_read32(LOONGARCH_CSR_EUEN);
@@ -26,6 +28,7 @@ void save_processor_state(void)
 
 void restore_processor_state(void)
 {
+	sync_counter();
 	csr_write32(saved_crmd, LOONGARCH_CSR_CRMD);
 	csr_write32(saved_prmd, LOONGARCH_CSR_PRMD);
 	csr_write32(saved_euen, LOONGARCH_CSR_EUEN);