Sorry, I missed this before submitting our v7. I'll respond properly in a bit...
On Mon, 31 Jul 2017 04:00:26 PDT (-0700), daniel.lezc...@linaro.org wrote: > On 11/07/2017 03:39, Palmer Dabbelt wrote: >> The RISC-V ISA defines a per-hart real-time clock and timer, which is >> present on all systems. The clock is accessed via the 'rdtime' >> pseudo-instruction (which reads a CSR), and the timer is set via an SBI >> call. >> >> This driver attempts to split out the RISC-V ISA specific mechanisms of >> accessing the hardware from the clocksource driver by taking a pair of >> function pointers to issue the actual RISC-V specific instructions. >> >> Signed-off-by: Palmer Dabbelt <pal...@dabbelt.com> >> --- > > [ ... ] > >> +#ifndef _LINUX_TIMER_RISCV_H >> +#define _LINUX_TIMER_RISCV_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. >> + */ > > Hi Palmer, > > The driver code must be self contained (eg. setup and irq handling). > > There are examples in the drivers/clocksource to stick on, for example > the jcore-pit.c or the mips-gic-timer.c drivers. > > I don't see the point to setup callbacks at init time. > > Thanks. > > -- Daniel > > >> +void timer_riscv_init(int cpu_id, >> + unsigned long riscv_timebase, >> + unsigned long long (*rdtime)(struct clocksource *), >> + int (*next_event)(unsigned long, struct >> clock_event_device *)); >> + >> +/* >> + * Looks up the clocksource or clock_even_device that cooresponds the given >> + * hart. >> + */ >> +struct clocksource *timer_riscv_source(int cpuid); >> +struct clock_event_device *timer_riscv_device(int cpu_id); >> + >> +#endif >>
