Hi Chris, On Thu, 2024-06-27 at 16:33 +1200, Chris Packham wrote: > The timer/counter block on the Realtek SoCs provides up to 5 timers. It > also includes a watchdog timer but this isn't being used currently (it > will be added as a separate wdt driver). Do you mean the watchdog timer supported by drivers/watchdog/realtek_otto_wdt.c? Or are you referring to another watchdog timer? > One timer will be used per CPU as a local clock event generator. An > additional timer will be used as an overal stable clocksource. > > Signed-off-by: Markus Stockhausen <markus.stockhausen@xxxxxx> > Signed-off-by: Sander Vanheule <sander@xxxxxxxxxxxxx> > Signed-off-by: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx> > --- For reference, I submitted a driver for the same hardware back in 2022, but didn't manage to follow up to finalize the submission: https://lore.kernel.org/all/cover.1642369117.git.sander@xxxxxxxxxxxxx/ > + > +/* Module initialization part. */ > +static DEFINE_PER_CPU(struct timer_of, rttm_to) = { > + .flags = TIMER_OF_BASE | TIMER_OF_CLOCK | > TIMER_OF_IRQ, > + .of_irq = { > + .flags = IRQF_PERCPU | IRQF_TIMER, In the original review of this code, I had some doubts about the use of IRQF_PERCPU. Maybe the people in Cc can shed some light on this. If I understand correctly, the SoC interrupts these timers use are not per-cpu interrupts. (For comparison, AFAICT the MIPS CPU interrupts are) > + .handler = rttm_timer_interrupt, > + }, > + .clkevt = { > + .rating = 400, > + .features = CLOCK_EVT_FEAT_PERIODIC | > CLOCK_EVT_FEAT_ONESHOT, If the use of IRQF_PERCPU is appropriate, I wonder if the driver should also use CLOCK_EVT_FEAT_PERCPU. Best, Sander
