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SubjectRe: [PATCH v8 4/6] clocksource: stm32: only use 32 bits timers
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On 14/11/2017 09:52, Benjamin Gaignard wrote:
> The clock driving counters is at 90MHz so the maximum period
> for 16 bis counters is around 750 ms which is a short period
> for a clocksource.

Isn't it 728us ?

> For 32 bits counters this period is close
> 47 secondes which is more acceptable.
>
> This patch remove 16 bits counters support and makes sure that
> they won't be probed anymore.
>
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> ---
> drivers/clocksource/timer-stm32.c | 26 ++++++++++++--------------
> 1 file changed, 12 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/clocksource/timer-stm32.c b/drivers/clocksource/timer-stm32.c
> index ae41a19..8173bcf 100644
> --- a/drivers/clocksource/timer-stm32.c
> +++ b/drivers/clocksource/timer-stm32.c
> @@ -83,9 +83,9 @@ static irqreturn_t stm32_clock_event_handler(int irq, void *dev_id)
> static int __init stm32_clockevent_init(struct device_node *node)
> {
> struct reset_control *rstc;
> - unsigned long max_delta;
> - int ret, bits, prescaler = 1;
> + unsigned long max_arr;
> struct timer_of *to;
> + int ret;
>
> to = kzalloc(sizeof(*to), GFP_KERNEL);
> if (!to)
> @@ -115,29 +115,27 @@ static int __init stm32_clockevent_init(struct device_node *node)
>
> /* Detect whether the timer is 16 or 32 bits */
> writel_relaxed(~0U, timer_of_base(to) + TIM_ARR);
> - max_delta = readl_relaxed(timer_of_base(to) + TIM_ARR);
> - if (max_delta == ~0U) {
> - prescaler = 1;
> - bits = 32;
> - } else {
> - prescaler = 1024;
> - bits = 16;
> + max_arr = readl_relaxed(timer_of_base(to) + TIM_ARR);
> + if (max_arr != ~0U) {
> + pr_err("32 bits timer is needed\n");
> + ret = -EINVAL;
> + goto deinit;
> }
> +
> writel_relaxed(0, timer_of_base(to) + TIM_ARR);
>
> - writel_relaxed(prescaler - 1, timer_of_base(to) + TIM_PSC);
> + writel_relaxed(0, timer_of_base(to) + TIM_PSC);
> writel_relaxed(TIM_EGR_UG, timer_of_base(to) + TIM_EGR);
> writel_relaxed(TIM_DIER_UIE, timer_of_base(to) + TIM_DIER);
> writel_relaxed(0, timer_of_base(to) + TIM_SR);
>
> clockevents_config_and_register(&to->clkevt,
> - timer_of_period(to), MIN_DELTA, max_delta);
> -
> - pr_info("%pOF: STM32 clockevent driver initialized (%d bits)\n",
> - node, bits);
> + timer_of_period(to), MIN_DELTA, ~0U);
>
> return 0;
>
> +deinit:
> + timer_of_exit(to);
> err:
> kfree(to);
> return ret;
>


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