Messages in this thread Patch in this message |  | | From | Nicolai Stange <> | Subject | [RFC v8 04/28] clocksource: em_sti: compute rate before registration | Date | Sat, 19 Nov 2016 17:00:31 +0100 |
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With the upcoming NTP correction related rate adjustments to be implemented in the clockevents core, the latter needs to get informed about every rate change of a clockevent device made after its registration.
Currently, em_sti violates this requirement in that it registers its clockevent device with a dummy rate and sets its final rate through clockevents_config() called from its ->set_state_oneshot().
This patch moves the setting of the clockevent device's rate to its registration.
I checked all current em_sti users in arch/arm/mach-shmobile and right now, none of them changes any rate in any clock tree relevant to em_sti after their respective time_init(). Since all em_sti instances are created after time_init(), none of them should ever observe any clock rate changes.
- Determine the ->rate value in em_sti_probe() at device probing rather than at first usage. - Set the clockevent device's rate at its registration. - Although not strictly necessary for the upcoming clockevent core changes, set the clocksource's rate at its registration for consistency.
Signed-off-by: Nicolai Stange <nicstange@gmail.com> ---
Notes: For a detailed analysis of the current em_sti users, please see https://nicst.de/ced-clk-rate-change-analysis/em_sti-cgitted.html Compile-only tested on ARCH=arm.
drivers/clocksource/em_sti.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-)
diff --git a/drivers/clocksource/em_sti.c b/drivers/clocksource/em_sti.c index 46750c0..6168d18 100644 --- a/drivers/clocksource/em_sti.c +++ b/drivers/clocksource/em_sti.c @@ -205,13 +205,9 @@ static cycle_t em_sti_clocksource_read(struct clocksource *cs) static int em_sti_clocksource_enable(struct clocksource *cs) { - int ret; struct em_sti_priv *p = cs_to_em_sti(cs); - ret = em_sti_start(p, USER_CLOCKSOURCE); - if (!ret) - __clocksource_update_freq_hz(cs, p->rate); - return ret; + return em_sti_start(p, USER_CLOCKSOURCE); } static void em_sti_clocksource_disable(struct clocksource *cs) @@ -240,8 +236,7 @@ static int em_sti_register_clocksource(struct em_sti_priv *p) dev_info(&p->pdev->dev, "used as clock source\n"); - /* Register with dummy 1 Hz value, gets updated in ->enable() */ - clocksource_register_hz(cs, 1); + clocksource_register_hz(cs, p->rate); return 0; } @@ -263,7 +258,6 @@ static int em_sti_clock_event_set_oneshot(struct clock_event_device *ced) dev_info(&p->pdev->dev, "used for oneshot clock events\n"); em_sti_start(p, USER_CLOCKEVENT); - clockevents_config(&p->ced, p->rate); return 0; } @@ -294,8 +288,7 @@ static void em_sti_register_clockevent(struct em_sti_priv *p) dev_info(&p->pdev->dev, "used for clock events\n"); - /* Register with dummy 1 Hz value, gets updated in ->set_state_oneshot() */ - clockevents_config_and_register(ced, 1, 2, 0xffffffff); + clockevents_config_and_register(ced, p->rate, 2, 0xffffffff); } static int em_sti_probe(struct platform_device *pdev) @@ -344,11 +337,22 @@ static int em_sti_probe(struct platform_device *pdev) goto err_clk_put; } + ret = clk_enable(p->clk); + if (ret < 0) { + dev_err(&p->pdev->dev, "cannot enable clock\n"); + goto err_clk_unprepare; + } + p->rate = clk_get_rate(p->clk); + clk_disable(p->clk); + raw_spin_lock_init(&p->lock); em_sti_register_clockevent(p); em_sti_register_clocksource(p); return 0; +err_clk_unprepare: + clk_unprepare(p->clk); + err_clk_put: clk_put(p->clk); return ret; -- 2.10.2
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