[PATCH] clocksource: riscv: Patch riscv_clock_next_event() jump before first use

[Matt Evans]

Hi Conor,

> On 1 Feb 2023, at 19:21, Conor Dooley <conor at kernel.org> wrote:
> 
> Hey Matt,
> 
> On Wed, Feb 01, 2023 at 06:41:52PM +0000, Matt Evans wrote:
>> A static key is used to select between SBI and Sstc timer usage in
>> riscv_clock_next_event(), but currently the direction is resolved
>> after cpuhp_setup_state() is called (which sets the next event).  The
>> first event will therefore fall through the sbi_set_timer() path; this
>> breaks Sstc-only systems.  So, apply the jump patching before first
>> use.
>> 
>> Signed-off-by: Matt Evans <mev at rivosinc.com>
> 
> Your logic in this patch looks grand, just got two process bits for ya.
> Firstly, you're missing a fixes tag, which I would imagine is:
> Fixes: 9f7a8ff6391f ("RISC-V: Prefer sstc extension if available")
> 
> Also, of late, the clocksource maintainers, who you have not CCed,
> have been the ones that pick up patches that only touch this driver.
> Might be worth a resubmission CCing them...

Both good points, many thanks.  True, it fixes(:) 9f7a8ff6391f, and TIL on the shepherd chain.  I’ll re-send.


Cheers,


Matt

> 
> Cheers,
> Conor.
> 
>> ---
>> drivers/clocksource/timer-riscv.c | 10 +++++-----
>> 1 file changed, 5 insertions(+), 5 deletions(-)
>> 
>> diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
>> index 969a552da8d2..a36d173fd6cd 100644
>> --- a/drivers/clocksource/timer-riscv.c
>> +++ b/drivers/clocksource/timer-riscv.c
>> @@ -177,6 +177,11 @@ static int __init riscv_timer_init_dt(struct device_node *n)
>> 		return error;
>> 	}
>> 
>> +	if (riscv_isa_extension_available(NULL, SSTC)) {
>> +		pr_info("Timer interrupt in S-mode is available via sstc extension\n");
>> +		static_branch_enable(&riscv_sstc_available);
>> +	}
>> +
>> 	error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
>> 			 "clockevents/riscv/timer:starting",
>> 			 riscv_timer_starting_cpu, riscv_timer_dying_cpu);
>> @@ -184,11 +189,6 @@ static int __init riscv_timer_init_dt(struct device_node *n)
>> 		pr_err("cpu hp setup state failed for RISCV timer [%d]\n",
>> 		       error);
>> 
>> -	if (riscv_isa_extension_available(NULL, SSTC)) {
>> -		pr_info("Timer interrupt in S-mode is available via sstc extension\n");
>> -		static_branch_enable(&riscv_sstc_available);
>> -	}
>> -
>> 	return error;
>> }
>> 
>> -- 
>> 2.30.2
>> 
>> 
>> 
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