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Message-ID: <20251004015623.7019-3-raskar.shree97@gmail.com>
Date: Sat, 4 Oct 2025 07:26:23 +0530
From: Shrikant Raskar <raskar.shree97@...il.com>
To: jic23@...nel.org,
robh@...nel.org,
krzk+dt@...nel.org,
conor+dt@...nel.org
Cc: dlechner@...libre.com,
nuno.sa@...log.com,
andy@...nel.org,
matt@...ostay.sg,
skhan@...uxfoundation.org,
david.hunter.linux@...il.com,
linux-iio@...r.kernel.org,
devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-kernel-mentees@...ts.linux.dev,
Shrikant Raskar <raskar.shree97@...il.com>
Subject: [PATCH 2/2] iio: health: max30100: Add pulse-width configuration via DT
The MAX30100 driver previously hardcoded the SPO2 pulse width to
1600us. This patch adds support for reading the pulse width from
device tree (`maxim,pulse-width`) and programming it into the SPO2
configuration register.
If no property is provided, the driver falls back to 1600us to
preserve existing behavior.
Testing:
Hardware: Raspberry Pi 3B + MAX30100 breakout
Verified DT property read in probe()
Confirmed SPO2_CONFIG register written correctly using regmap_read()
Signed-off-by: Shrikant Raskar <raskar.shree97@...il.com>
---
drivers/iio/health/max30100.c | 39 +++++++++++++++++++++++++++++++++--
1 file changed, 37 insertions(+), 2 deletions(-)
diff --git a/drivers/iio/health/max30100.c b/drivers/iio/health/max30100.c
index 814f521e47ae..2b3348c75beb 100644
--- a/drivers/iio/health/max30100.c
+++ b/drivers/iio/health/max30100.c
@@ -5,7 +5,6 @@
* Copyright (C) 2015, 2018
* Author: Matt Ranostay <matt.ranostay@...sulko.com>
*
- * TODO: enable pulse length controls via device tree properties
*/
#include <linux/module.h>
@@ -54,6 +53,9 @@
#define MAX30100_REG_SPO2_CONFIG 0x07
#define MAX30100_REG_SPO2_CONFIG_100HZ BIT(2)
#define MAX30100_REG_SPO2_CONFIG_HI_RES_EN BIT(6)
+#define MAX30100_REG_SPO2_CONFIG_200US 0x0
+#define MAX30100_REG_SPO2_CONFIG_400US 0x1
+#define MAX30100_REG_SPO2_CONFIG_800US 0x2
#define MAX30100_REG_SPO2_CONFIG_1600US 0x3
#define MAX30100_REG_LED_CONFIG 0x09
@@ -306,19 +308,52 @@ static int max30100_led_init(struct max30100_data *data)
MAX30100_REG_LED_CONFIG_LED_MASK, reg);
}
+static int max30100_get_pulse_width(unsigned int pwidth_us)
+{
+ switch (pwidth_us) {
+ case 200:
+ return MAX30100_REG_SPO2_CONFIG_200US;
+ case 400:
+ return MAX30100_REG_SPO2_CONFIG_400US;
+ case 800:
+ return MAX30100_REG_SPO2_CONFIG_800US;
+ case 1600:
+ return MAX30100_REG_SPO2_CONFIG_1600US;
+ default:
+ return -EINVAL;
+ }
+}
+
static int max30100_chip_init(struct max30100_data *data)
{
int ret;
+ unsigned int pulse_us;
+ unsigned int pulse_width;
+ struct device *dev = &data->client->dev;
/* setup LED current settings */
ret = max30100_led_init(data);
if (ret)
return ret;
+ /* Get pulse width from DT, default = 1600us */
+ ret = device_property_read_u32(dev, "maxim,pulse-width", &pulse_us);
+ if (ret) {
+ dev_warn(dev, "no pulse-width defined, defaulting to 1600us\n");
+ pulse_width = MAX30100_REG_SPO2_CONFIG_1600US;
+ } else {
+ pulse_width = max30100_get_pulse_width(pulse_us);
+ if (pulse_width < 0) {
+ dev_err(dev, "invalid pulse-width %u\n", pulse_us);
+ return pulse_width;
+ }
+ }
+
/* enable hi-res SPO2 readings at 100Hz */
ret = regmap_write(data->regmap, MAX30100_REG_SPO2_CONFIG,
MAX30100_REG_SPO2_CONFIG_HI_RES_EN |
- MAX30100_REG_SPO2_CONFIG_100HZ);
+ MAX30100_REG_SPO2_CONFIG_100HZ |
+ pulse_width);
if (ret)
return ret;
--
2.43.0
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