| Message ID | 20200818032814.15968-3-zhukeqian1@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | clocksource: arm_arch_timer: Some fixes | expand |
On 2020-08-18 04:28, Keqian Zhu wrote: > ARM virtual counter supports event stream, it can only trigger an event > when the trigger bit (the value of CNTKCTL_EL1.EVNTI) of CNTVCT_EL0 > changes, > so the actual period of event stream is 2^(cntkctl_evnti + 1). For > example, > when the trigger bit is 0, then virtual counter trigger an event for > every > two cycles. > > Fixes: 037f637767a8 ("drivers: clocksource: add support for > ARM architected timer event stream") Fixes: tags should on a single line. > Suggested-by: Marc Zyngier <maz@kernel.org> > Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com> > --- > drivers/clocksource/arm_arch_timer.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/drivers/clocksource/arm_arch_timer.c > b/drivers/clocksource/arm_arch_timer.c > index 777d38c..e3b2ee0 100644 > --- a/drivers/clocksource/arm_arch_timer.c > +++ b/drivers/clocksource/arm_arch_timer.c > @@ -824,10 +824,14 @@ static void arch_timer_configure_evtstream(void) > { > int evt_stream_div, pos; > > - /* Find the closest power of two to the divisor */ > - evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ; > + /* > + * Find the closest power of two to the divisor. As the event > + * stream can at most be generated at half the frequency of the > + * counter, use half the frequency when computing the divider. > + */ > + evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ / 2; > pos = fls(evt_stream_div); > - if (pos > 1 && !(evt_stream_div & (1 << (pos - 2)))) > + if ((pos == 1) || (pos > 1 && !(evt_stream_div & (1 << (pos - 2))))) > pos--; You don't explain why you are special-casing pos == 1. > /* enable event stream */ > arch_timer_evtstrm_enable(min(pos, 15)); Also, please Cc the subsystem maintainers: CLOCKSOURCE, CLOCKEVENT DRIVERS M: Daniel Lezcano <daniel.lezcano@linaro.org> M: Thomas Gleixner <tglx@linutronix.de> L: linux-kernel@vger.kernel.org S: Supported T: git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/core F: Documentation/devicetree/bindings/timer/ F: drivers/clocksource/ Thanks, M.
Hi Marc, On 2020/12/3 22:57, Marc Zyngier wrote: > On 2020-08-18 04:28, Keqian Zhu wrote: >> ARM virtual counter supports event stream, it can only trigger an event >> when the trigger bit (the value of CNTKCTL_EL1.EVNTI) of CNTVCT_EL0 changes, >> so the actual period of event stream is 2^(cntkctl_evnti + 1). For example, >> when the trigger bit is 0, then virtual counter trigger an event for every >> two cycles. >> >> Fixes: 037f637767a8 ("drivers: clocksource: add support for >> ARM architected timer event stream") > > Fixes: tags should on a single line. Will do. > >> Suggested-by: Marc Zyngier <maz@kernel.org> >> Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com> >> --- >> drivers/clocksource/arm_arch_timer.c | 10 +++++++--- >> 1 file changed, 7 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/clocksource/arm_arch_timer.c >> b/drivers/clocksource/arm_arch_timer.c >> index 777d38c..e3b2ee0 100644 >> --- a/drivers/clocksource/arm_arch_timer.c >> +++ b/drivers/clocksource/arm_arch_timer.c >> @@ -824,10 +824,14 @@ static void arch_timer_configure_evtstream(void) >> { >> int evt_stream_div, pos; >> >> - /* Find the closest power of two to the divisor */ >> - evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ; >> + /* >> + * Find the closest power of two to the divisor. As the event >> + * stream can at most be generated at half the frequency of the >> + * counter, use half the frequency when computing the divider. >> + */ >> + evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ / 2; >> pos = fls(evt_stream_div); >> - if (pos > 1 && !(evt_stream_div & (1 << (pos - 2)))) >> + if ((pos == 1) || (pos > 1 && !(evt_stream_div & (1 << (pos - 2))))) >> pos--; > > You don't explain why you are special-casing pos == 1. The logic is not clear here, I will try to reform it. > >> /* enable event stream */ >> arch_timer_evtstrm_enable(min(pos, 15)); > > Also, please Cc the subsystem maintainers: > > CLOCKSOURCE, CLOCKEVENT DRIVERS > M: Daniel Lezcano <daniel.lezcano@linaro.org> > M: Thomas Gleixner <tglx@linutronix.de> > L: linux-kernel@vger.kernel.org > S: Supported > T: git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/core > F: Documentation/devicetree/bindings/timer/ > F: drivers/clocksource/ > Will do. > Thanks, > > M. Thanks, Keqian
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c index 777d38c..e3b2ee0 100644 --- a/drivers/clocksource/arm_arch_timer.c +++ b/drivers/clocksource/arm_arch_timer.c @@ -824,10 +824,14 @@ static void arch_timer_configure_evtstream(void) { int evt_stream_div, pos; - /* Find the closest power of two to the divisor */ - evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ; + /* + * Find the closest power of two to the divisor. As the event + * stream can at most be generated at half the frequency of the + * counter, use half the frequency when computing the divider. + */ + evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ / 2; pos = fls(evt_stream_div); - if (pos > 1 && !(evt_stream_div & (1 << (pos - 2)))) + if ((pos == 1) || (pos > 1 && !(evt_stream_div & (1 << (pos - 2))))) pos--; /* enable event stream */ arch_timer_evtstrm_enable(min(pos, 15));
ARM virtual counter supports event stream, it can only trigger an event when the trigger bit (the value of CNTKCTL_EL1.EVNTI) of CNTVCT_EL0 changes, so the actual period of event stream is 2^(cntkctl_evnti + 1). For example, when the trigger bit is 0, then virtual counter trigger an event for every two cycles. Fixes: 037f637767a8 ("drivers: clocksource: add support for ARM architected timer event stream") Suggested-by: Marc Zyngier <maz@kernel.org> Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com> --- drivers/clocksource/arm_arch_timer.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)