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Message-ID: <7c50613c-e48b-4e94-8fae-bf5d2227df0b@ti.com>
Date: Thu, 7 Aug 2025 12:37:34 -0500
From: Andrew Davis <afd@...com>
To: Gokul Praveen <g-praveen@...com>, <daniel.lezcano@...aro.org>,
<linux-kernel@...r.kernel.org>, <u-kumar1@...com>
Subject: Re: [PATCH] clocksource: timer-ti-dm : Capture functionality for OMAP
DM timer
On 8/7/25 7:32 AM, Gokul Praveen wrote:
> Add PWM capture function in DM timer driver.
>
> OMAP DM timer hardware supports capture feature.It can be used to
> timestamp events (falling/rising edges) detected on input signal.
>
> Signed-off-by: Gokul Praveen <g-praveen@...com>
> ---
> Precondition : Before calling driver API,it is assumed that the
> capture signal is active else both duty cycle
> and period returned by driver will not be valid.
> ---
> drivers/clocksource/timer-ti-dm.c | 127 ++++++++++++++++++++-
> include/linux/platform_data/dmtimer-omap.h | 4 +
> 2 files changed, 129 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clocksource/timer-ti-dm.c b/drivers/clocksource/timer-ti-dm.c
> index e9e32df6b566..a4bf72c850b5 100644
> --- a/drivers/clocksource/timer-ti-dm.c
> +++ b/drivers/clocksource/timer-ti-dm.c
> @@ -31,6 +31,7 @@
> #include <linux/platform_data/dmtimer-omap.h>
>
> #include <clocksource/timer-ti-dm.h>
> +#include <linux/delay.h>
>
> /*
> * timer errata flags
> @@ -836,6 +837,49 @@ static int omap_dm_timer_set_match(struct omap_dm_timer *cookie, int enable,
> return 0;
> }
>
> +static int omap_dm_timer_set_cap(struct omap_dm_timer *cookie,
> + int autoreload, bool config_period)
> +{
> + struct dmtimer *timer;
> + struct device *dev;
> + int rc;
> + u32 l;
> +
> + timer = to_dmtimer(cookie);
> + if (unlikely(!timer))
> + return -EINVAL;
> +
> + dev = &timer->pdev->dev;
Do this assignment up where the var is declared
> + rc = pm_runtime_resume_and_get(dev);
> +
Extra newline, fix this everywhere
> + if (rc)
> + return rc;
> + /*
> + * 1. Select autoreload mode. TIMER_TCLR[1] AR bit.
> + * 2. TIMER_TCLR[14]: Sets the functionality of the TIMER IO pin.
> + * 3. TIMER_TCLR[13] : Capture mode select bit.
> + * 3. TIMER_TCLR[9-8] : Select transition capture mode.
> + */
> +
> + l = dmtimer_read(timer, OMAP_TIMER_CTRL_REG);
> +
> + if (autoreload)
> + l |= OMAP_TIMER_CTRL_AR;
> +
> + l |= OMAP_TIMER_CTRL_CAPTMODE | OMAP_TIMER_CTRL_GPOCFG;
> +
> + if (config_period == true)
> + l |= OMAP_TIMER_CTRL_TCM_LOWTOHIGH; /*Time Period config*/
Add space around /* xxx */ in your comments, do this everywhere
> + else
> + l |= OMAP_TIMER_CTRL_TCM_BOTHEDGES; /*Duty Cycle config*/
> +
> + dmtimer_write(timer, OMAP_TIMER_CTRL_REG, l);
> +
> + pm_runtime_put_sync(dev);
> +
> + return 0;
> +}
> +
> static int omap_dm_timer_set_pwm(struct omap_dm_timer *cookie, int def_on,
> int toggle, int trigger, int autoreload)
> {
> @@ -1023,23 +1067,99 @@ static unsigned int omap_dm_timer_read_counter(struct omap_dm_timer *cookie)
> return __omap_dm_timer_read_counter(timer);
> }
>
> +static inline unsigned int __omap_dm_timer_cap(struct dmtimer *timer, int idx)
> +{
> + return idx == 0 ? dmtimer_read(timer, OMAP_TIMER_CAPTURE_REG) :
> + dmtimer_read(timer, OMAP_TIMER_CAPTURE2_REG);
> +}
> +
> static int omap_dm_timer_write_counter(struct omap_dm_timer *cookie, unsigned int value)
> {
> struct dmtimer *timer;
> + struct device *dev;
>
> timer = to_dmtimer(cookie);
> - if (unlikely(!timer || !atomic_read(&timer->enabled))) {
> - pr_err("%s: timer not available or enabled.\n", __func__);
> + if (unlikely(!timer)) {
> + pr_err("%s: timer not available.\n", __func__);
> return -EINVAL;
> }
>
> + dev = &timer->pdev->dev;
> +
> + pm_runtime_resume_and_get(dev);
> dmtimer_write(timer, OMAP_TIMER_COUNTER_REG, value);
> + pm_runtime_put_sync(dev);
>
> /* Save the context */
> timer->context.tcrr = value;
> return 0;
> }
>
> +/**
> + * omap_dm_timer_cap_counter() - Calculate the high count or period count depending on the
> + * configuration.
> + * @cookie:Pointer to OMAP DM timer
> + * @is_period:Whether to configure timer in period or duty cycle mode
> + *
> + * Return high count or period count if timer is enabled else appropriate error.
> + */
> +static unsigned int omap_dm_timer_cap_counter(struct omap_dm_timer *cookie, bool is_period)
> +{
> + struct dmtimer *timer;
> + unsigned int cap1 = 0;
> + unsigned int cap2 = 0;
> + u32 l, ret;
> +
> + timer = to_dmtimer(cookie);
> + if (unlikely(!timer || !atomic_read(&timer->enabled))) {
> + pr_err("%s:timer is not available or enabled.%p\n", __func__, (void *)timer);
> + return -EINVAL;
> + }
> +
> + /*Stop the timer*/
> + omap_dm_timer_stop(cookie);
> +
> + /* Clear the timer counter value to 0 */
> + ret = omap_dm_timer_write_counter(cookie, 0);
> +
> + if (ret)
> + return ret;
> +
> + /*Sets the timer capture configuration for duty cycle calculation*/
> + if (is_period == false)
> + ret = omap_dm_timer_set_cap(cookie, true, false);
> +
> + /*Sets the timer capture configuration for period calculation*/
> + else
> + ret = omap_dm_timer_set_cap(cookie, true, true);
> +
The above 8 lines could just be:
ret = omap_dm_timer_set_cap(cookie, true, is_period);
Andrew
> + if (ret) {
> + pr_err("%s: Failed to set timer capture configuration.\n", __func__);
> + return ret;
> + }
> + /*Start the timer*/
> + omap_dm_timer_start(cookie);
> +
> + /*
> + * 1 sec delay is given so as to provide
> + * enough time to capture low frequency signals.
> + */
> + msleep(1000);
> +
> + cap1 = __omap_dm_timer_cap(timer, 0);
> + cap2 = __omap_dm_timer_cap(timer, 1);
> +
> + /*
> + * Clears the TCLR configuration.
> + * The start bit must be set to 1 as the timer is already in start mode.
> + */
> + l = dmtimer_read(timer, OMAP_TIMER_CTRL_REG);
> + l &= ~(0xffff) | 0x1;
> + dmtimer_write(timer, OMAP_TIMER_CTRL_REG, l);
> +
> + return (cap2-cap1);
> +}
> +
> static int __maybe_unused omap_dm_timer_runtime_suspend(struct device *dev)
> {
> struct dmtimer *timer = dev_get_drvdata(dev);
> @@ -1246,6 +1366,9 @@ static const struct omap_dm_timer_ops dmtimer_ops = {
> .write_counter = omap_dm_timer_write_counter,
> .read_status = omap_dm_timer_read_status,
> .write_status = omap_dm_timer_write_status,
> + .set_cap = omap_dm_timer_set_cap,
> + .get_cap_status = omap_dm_timer_get_pwm_status,
> + .read_cap = omap_dm_timer_cap_counter,
> };
>
> static const struct dmtimer_platform_data omap3plus_pdata = {
> diff --git a/include/linux/platform_data/dmtimer-omap.h b/include/linux/platform_data/dmtimer-omap.h
> index 95d852aef130..726d89143842 100644
> --- a/include/linux/platform_data/dmtimer-omap.h
> +++ b/include/linux/platform_data/dmtimer-omap.h
> @@ -36,9 +36,13 @@ struct omap_dm_timer_ops {
> int (*set_pwm)(struct omap_dm_timer *timer, int def_on,
> int toggle, int trigger, int autoreload);
> int (*get_pwm_status)(struct omap_dm_timer *timer);
> + int (*set_cap)(struct omap_dm_timer *timer,
> + int autoreload, bool config_period);
> + int (*get_cap_status)(struct omap_dm_timer *timer);
> int (*set_prescaler)(struct omap_dm_timer *timer, int prescaler);
>
> unsigned int (*read_counter)(struct omap_dm_timer *timer);
> + unsigned int (*read_cap)(struct omap_dm_timer *timer, bool is_period);
> int (*write_counter)(struct omap_dm_timer *timer,
> unsigned int value);
> unsigned int (*read_status)(struct omap_dm_timer *timer);
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