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riscv: don't use the rdtime(h) pseudo-instructions 

If we just use the CSRs that these map to directly the code is simpler
and doesn't require extra inline assembly code.  Also fix up the top-level
comment in timer-riscv.c to not talk about the cycle count or mention
details of the clocksource interface, of which this file is just a
consumer.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
This commit is contained in:
Christoph Hellwig 2019-08-21 23:58:36 +09:00 committed by Paul Walmsley
parent f5bf645d10
commit 2f12dbf190
2 changed files with 25 additions and 36 deletions
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44
arch/riscv/include/asm/timex.h
View File

@ -6,43 +6,41 @@
#ifndef _ASM_RISCV_TIMEX_H #ifndef _ASM_RISCV_TIMEX_H
#define _ASM_RISCV_TIMEX_H #define _ASM_RISCV_TIMEX_H
#include <asm/param.h> #include <asm/csr.h>
typedef unsigned long cycles_t; typedef unsigned long cycles_t;
static inline cycles_t get_cycles_inline(void) static inline cycles_t get_cycles(void)
{ {
cycles_t n; return csr_read(CSR_TIME);
__asm__ __volatile__ (
"rdtime %0"
: "=r" (n));
return n;
} }
#define get_cycles get_cycles_inline #define get_cycles get_cycles
#ifdef CONFIG_64BIT #ifdef CONFIG_64BIT
static inline uint64_t get_cycles64(void) static inline u64 get_cycles64(void)
{ {
return get_cycles(); return get_cycles();
} }
#else #else /* CONFIG_64BIT */
static inline uint64_t get_cycles64(void) static inline u32 get_cycles_hi(void)
{ {
u32 lo, hi, tmp; return csr_read(CSR_TIMEH);
__asm__ __volatile__ ( }
"1:\n"
"rdtimeh %0\n" static inline u64 get_cycles64(void)
"rdtime %1\n" {
"rdtimeh %2\n" u32 hi, lo;
"bne %0, %2, 1b"
: "=&r" (hi), "=&r" (lo), "=&r" (tmp)); do {
hi = get_cycles_hi();
lo = get_cycles();
} while (hi != get_cycles_hi());
return ((u64)hi << 32) | lo; return ((u64)hi << 32) | lo;
} }
#endif #endif /* CONFIG_64BIT */
#define ARCH_HAS_READ_CURRENT_TIMER #define ARCH_HAS_READ_CURRENT_TIMER
static inline int read_current_timer(unsigned long *timer_val) static inline int read_current_timer(unsigned long *timer_val)
{ {
*timer_val = get_cycles(); *timer_val = get_cycles();

17
drivers/clocksource/timer-riscv.c
View File

@ -2,6 +2,10 @@
/* /*
* Copyright (C) 2012 Regents of the University of California * Copyright (C) 2012 Regents of the University of California
* Copyright (C) 2017 SiFive * Copyright (C) 2017 SiFive
*
* All RISC-V systems have a timer attached to every hart. These timers can be
* read from the "time" and "timeh" CSRs, and can use the SBI to setup
* events.
*/ */
#include <linux/clocksource.h> #include <linux/clocksource.h>
#include <linux/clockchips.h> #include <linux/clockchips.h>
@ -12,19 +16,6 @@
#include <asm/smp.h> #include <asm/smp.h>
#include <asm/sbi.h> #include <asm/sbi.h>
/*
* All RISC-V systems have a timer attached to every hart. These timers can be
* read by the 'rdcycle' pseudo instruction, and can use the SBI to setup
* events. In order to abstract the architecture-specific timer reading and
* setting functions away from the clock event insertion code, we provide
* function pointers to the clockevent subsystem that perform two basic
* operations: rdtime() reads the timer on the current CPU, and
* next_event(delta) sets the next timer event to 'delta' cycles in the future.
* As the timers are inherently a per-cpu resource, these callbacks perform
* operations on the current hart. There is guaranteed to be exactly one timer
* per hart on all RISC-V systems.
*/
static int riscv_clock_next_event(unsigned long delta, static int riscv_clock_next_event(unsigned long delta,
struct clock_event_device *ce) struct clock_event_device *ce)
{ {