Re: [PATCH] clocksource: timer-ti-dm : Capture functionality for OMAP DM timer
From: Gokul Praveen
Date: Fri Aug 08 2025 - 03:42:08 EST
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@xxxxxx>
---
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);