Messages in this thread | | | Date | Wed, 27 Mar 2024 00:33:35 +0800 | From | Jisheng Zhang <> | Subject | Re: [PATCH 5/5] clocksource/drivers/timer-clint: Add T-Head C9xx clint support |
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On Tue, Mar 26, 2024 at 09:31:14AM +0800, Jisheng Zhang wrote: > On Tue, Mar 26, 2024 at 09:25:09AM +0800, Jisheng Zhang wrote: > > On Mon, Mar 25, 2024 at 03:22:11PM -0700, Bo Gan wrote: > > > On 3/25/24 9:40 AM, Jisheng Zhang wrote: > > > > The mtimecmp in T-Head C9xx clint only supports 32bit read/write, > > > > implement such support. > > > > > > > > Signed-off-by: Jisheng Zhang <jszhang@kernel.org> > > > > --- > > > > drivers/clocksource/timer-clint.c | 24 ++++++++++++++++++++++++ > > > > 1 file changed, 24 insertions(+) > > > > > > > > diff --git a/drivers/clocksource/timer-clint.c b/drivers/clocksource/timer-clint.c > > > > index 4537c77e623c..71188732e8a3 100644 > > > > --- a/drivers/clocksource/timer-clint.c > > > > +++ b/drivers/clocksource/timer-clint.c > > > > @@ -34,6 +34,7 @@ static unsigned int clint_ipi_irq; > > > > static u64 __iomem *clint_timer_cmp; > > > > static unsigned long clint_timer_freq; > > > > static unsigned int clint_timer_irq; > > > > +static bool is_c900_clint; > > > > #ifdef CONFIG_SMP > > > > static void clint_send_ipi(unsigned int cpu) > > > > @@ -88,6 +89,19 @@ static int clint_clock_next_event(unsigned long delta, > > > > return 0; > > > > } > > > > +static int c900_clint_clock_next_event(unsigned long delta, > > > > + struct clock_event_device *ce) > > > > +{ > > > > + void __iomem *r = clint_timer_cmp + > > > > + cpuid_to_hartid_map(smp_processor_id()); > > > > + u64 val = clint_get_cycles64() + delta; > > > > + > > > > + csr_set(CSR_IE, IE_TIE); > > > Perhaps you should do a writel_relaxed(-1, r) here. just like openSBI, because the update > > > to mtimecmp is now split into 2 parts. > > > https://github.com/riscv-software-src/opensbi/blob/v1.4/lib/utils/timer/aclint_mtimer.c#L54
Hi,
The reason of "writel_relaxed(-1, r)" is to avoid spurious irq, this is well explained by riscv spec. After more thoughts, this is not needed here in linux kernel because set_next_event() is only called in ISR, so the irq has been disabled, we don't suffer from spurious irq problem.
Thanks > > > > Thanks, I also noticed the mtimecmp update on 32bit platforms doesn't > > strictly follow the riscv spec: > > > > # New comparand is in a1:a0. > > li t0, -1 > > la t1, mtimecmp > > sw t0, 0(t1) # No smaller than old value. > > sw a1, 4(t1) # No smaller than new value. > > sw a0, 0(t1) # New value. > > > > So A new bug fix patch will be added in v2. > > > > wait, I found a similar bug in timer-riscv.c, and since these are fixes, > I'd like to send fixes as a seperate series. I'm cooking the patches > > > > > > > > > > + writel_relaxed(val, r); > > > > + writel_relaxed(val >> 32, r + 4); > > > > + return 0; > > > > +} > > > > +> static DEFINE_PER_CPU(struct clock_event_device, clint_clock_event) = { > > > > .name = "clint_clockevent", > > > > .features = CLOCK_EVT_FEAT_ONESHOT, > > > > @@ -99,6 +113,9 @@ static int clint_timer_starting_cpu(unsigned int cpu) > > > > { > > > > struct clock_event_device *ce = per_cpu_ptr(&clint_clock_event, cpu); > > > > + if (is_c900_clint) > > > > + ce->set_next_event = c900_clint_clock_next_event; > > > > + > > > > ce->cpumask = cpumask_of(cpu); > > > > clockevents_config_and_register(ce, clint_timer_freq, 100, ULONG_MAX); > > > > @@ -233,5 +250,12 @@ static int __init clint_timer_init_dt(struct device_node *np) > > > > return rc; > > > > } > > > > +static int __init c900_clint_timer_init_dt(struct device_node *np) > > > > +{ > > > > + is_c900_clint = true; > > > > + return clint_timer_init_dt(np); > > > > +} > > > > + > > > > TIMER_OF_DECLARE(clint_timer, "riscv,clint0", clint_timer_init_dt); > > > > TIMER_OF_DECLARE(clint_timer1, "sifive,clint0", clint_timer_init_dt); > > > > +TIMER_OF_DECLARE(clint_timer2, "thead,c900-clint", clint_timer_init_dt); > > > > > > > Better use a more generic term to describe the fact that mtimecmp doesn't support > > > 64-bit mmio, just like what openSBI is currently doing, instead of making it c900 specific: > > > > This has been mentioned in commit msg, but adding a code comment seems fine. > > > > > > https://github.com/riscv-software-src/opensbi/blob/v1.4/lib/utils/timer/fdt_timer_mtimer.c#L152 > > > > > > Then your `is_c900_clint` becomes something like `timecmp_64bit_mmio`. > > > > > > Bo
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