Re: [PATCH] clocksource: timer-ti-dm : Capture functionality for OMAP DM timer

[Gokul Praveen <g-praveen@ti.com>]

Hi Andrew,

On 07/08/25 23:07, Andrew Davis wrote:
> 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@ti.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
> 
Actually the timer is initialized after that in the to_dmtimer function.

So wouldn't initializing the 'dev' variable before that cause issues.

>> +    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
> 

Sure Andrew.

>> +    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
> 

Sure Andrew.

Regards
Gokul
>> +    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);
>