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Message-ID: <20190821151529.42rwd5lkzknv7ti2@linutronix.de>
Date: Wed, 21 Aug 2019 17:15:30 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc: Alexander Dahl <ada@...rsis.com>, linux-rt-users@...r.kernel.org,
Thomas Gleixner <tglx@...utronix.de>,
LKML <linux-kernel@...r.kernel.org>,
Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [ANNOUNCE] v5.2.9-rt3
On 2019-08-21 16:58:37 [+0200], Alexandre Belloni wrote:
> On 21/08/2019 16:42:30+0200, Sebastian Andrzej Siewior wrote:
> > On 2019-08-21 16:21:10 [+0200], Alexandre Belloni wrote:
> > > I'm not sure it is worth it as the issue is introduced by
> > > clocksource-tclib-allow-higher-clockrates.patch. Shouldn't we fix it
> > > directly?
> >
> > you want to get rid of CONFIG_ATMEL_TCB_CLKSRC_USE_SLOW_CLOCK and use
> > the highest possible frequency by default?
> >
>
> No, I meant the issue fixed by clocksource-tclib-add-proper-depend.patch
> is introduced by clocksource-tclib-allow-higher-clockrates.patch so I
> would think fixing clocksource-tclib-allow-higher-clockrates.patch is
> preferable than having a separate patch.
>
> But maybe you meant you wanted a patch to fix
> clocksource-tclib-allow-higher-clockrates.patch
got it. So clocksource-tclib-allow-higher-clockrates.patch becomes:
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -424,11 +424,18 @@ config ATMEL_ST
config ATMEL_TCB_CLKSRC
bool "Atmel TC Block timer driver" if COMPILE_TEST
- depends on HAS_IOMEM
+ depends on HAS_IOMEM && ATMEL_TCLIB
select TIMER_OF if OF
help
Support for Timer Counter Blocks on Atmel SoCs.
+config ATMEL_TCB_CLKSRC_USE_SLOW_CLOCK
+ bool "TC Block use 32 KiHz clock"
+ depends on ATMEL_TCB_CLKSRC
+ default y
+ help
+ Select this to use 32 KiHz base clock rate as TC block clock.
+
config CLKSRC_EXYNOS_MCT
bool "Exynos multi core timer driver" if COMPILE_TEST
depends on ARM || ARM64
--- a/drivers/clocksource/timer-atmel-tcb.c
+++ b/drivers/clocksource/timer-atmel-tcb.c
@@ -27,8 +27,7 @@
* this 32 bit free-running counter. the second channel is not used.
*
* - The third channel may be used to provide a 16-bit clockevent
- * source, used in either periodic or oneshot mode. This runs
- * at 32 KiHZ, and can handle delays of up to two seconds.
+ * source, used in either periodic or oneshot mode.
*
* REVISIT behavior during system suspend states... we should disable
* all clocks and save the power. Easily done for clockevent devices,
@@ -131,6 +130,7 @@ struct tc_clkevt_device {
struct clock_event_device clkevt;
struct clk *clk;
bool clk_enabled;
+ u32 freq;
void __iomem *regs;
};
@@ -139,13 +139,6 @@ static struct tc_clkevt_device *to_tc_cl
return container_of(clkevt, struct tc_clkevt_device, clkevt);
}
-/* For now, we always use the 32K clock ... this optimizes for NO_HZ,
- * because using one of the divided clocks would usually mean the
- * tick rate can never be less than several dozen Hz (vs 0.5 Hz).
- *
- * A divided clock could be good for high resolution timers, since
- * 30.5 usec resolution can seem "low".
- */
static u32 timer_clock;
static void tc_clk_disable(struct clock_event_device *d)
@@ -195,7 +188,7 @@ static int tc_set_oneshot(struct clock_e
tc_clk_enable(d);
- /* slow clock, count up to RC, then irq and stop */
+ /* count up to RC, then irq and stop */
writel(timer_clock | ATMEL_TC_CPCSTOP | ATMEL_TC_WAVE |
ATMEL_TC_WAVESEL_UP_AUTO, regs + ATMEL_TC_REG(2, CMR));
writel(ATMEL_TC_CPCS, regs + ATMEL_TC_REG(2, IER));
@@ -217,10 +210,10 @@ static int tc_set_periodic(struct clock_
*/
tc_clk_enable(d);
- /* slow clock, count up to RC, then irq and restart */
+ /* count up to RC, then irq and restart */
writel(timer_clock | ATMEL_TC_WAVE | ATMEL_TC_WAVESEL_UP_AUTO,
regs + ATMEL_TC_REG(2, CMR));
- writel((32768 + HZ / 2) / HZ, tcaddr + ATMEL_TC_REG(2, RC));
+ writel((tcd->freq + HZ / 2) / HZ, tcaddr + ATMEL_TC_REG(2, RC));
/* Enable clock and interrupts on RC compare */
writel(ATMEL_TC_CPCS, regs + ATMEL_TC_REG(2, IER));
@@ -246,7 +239,11 @@ static struct tc_clkevt_device clkevt =
.features = CLOCK_EVT_FEAT_PERIODIC |
CLOCK_EVT_FEAT_ONESHOT,
/* Should be lower than at91rm9200's system timer */
+#ifdef CONFIG_ATMEL_TCB_CLKSRC_USE_SLOW_CLOCK
.rating = 125,
+#else
+ .rating = 200,
+#endif
.set_next_event = tc_next_event,
.set_state_shutdown = tc_shutdown_clk_off,
.set_state_periodic = tc_set_periodic,
@@ -268,8 +265,9 @@ static irqreturn_t ch2_irq(int irq, void
return IRQ_NONE;
}
-static int __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
+static int __init setup_clkevents(struct atmel_tc *tc, int divisor_idx)
{
+ unsigned divisor = atmel_tc_divisors[divisor_idx];
int ret;
struct clk *t2_clk = tc->clk[2];
int irq = tc->irq[2];
@@ -290,7 +288,11 @@ static int __init setup_clkevents(struct
clkevt.regs = tc->regs;
clkevt.clk = t2_clk;
- timer_clock = clk32k_divisor_idx;
+ timer_clock = divisor_idx;
+ if (!divisor)
+ clkevt.freq = 32768;
+ else
+ clkevt.freq = clk_get_rate(t2_clk) / divisor;
clkevt.clkevt.cpumask = cpumask_of(0);
@@ -301,7 +303,7 @@ static int __init setup_clkevents(struct
return ret;
}
- clockevents_config_and_register(&clkevt.clkevt, 32768, 1, 0xffff);
+ clockevents_config_and_register(&clkevt.clkevt, clkevt.freq, 1, 0xffff);
return ret;
}
@@ -477,7 +479,11 @@ static int __init tcb_clksrc_init(struct
goto err_disable_t1;
/* channel 2: periodic and oneshot timer support */
+#ifdef CONFIG_ATMEL_TCB_CLKSRC_USE_SLOW_CLOCK
ret = setup_clkevents(&tc, clk32k_divisor_idx);
+#else
+ ret = setup_clkevents(&tc, best_divisor_idx);
+#endif
if (ret)
goto err_unregister_clksrc;
>
> Hopefully, one day we will have a solution for that upstream (i.e. being
> able to configure the clocksource and clockevent resolutions).
Hopefully.
Sebastian
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