linux-kernel - [RESEND PATCH v6 3/3] leds: tlc5925: Add support for non blocking operations

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Message-ID: <20220722081146.47262-4-jjhiblot@traphandler.com>
Date:   Fri, 22 Jul 2022 10:11:46 +0200
From:   Jean-Jacques Hiblot <jjhiblot@...phandler.com>
To:     <pavel@....cz>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>
CC:     <andy.shevchenko@...il.com>, <linux-leds@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Jean-Jacques Hiblot <jjhiblot@...phandler.com>
Subject: [RESEND PATCH v6 3/3] leds: tlc5925: Add support for non blocking operations

Settings multiple LEDs in a row can be a slow operation because of the
time required to acquire the bus and prepare the transfer.
And, in most cases, it is not required that the operation is synchronous.
Implementing the non-blocking brightness_set() for such cases.
A work queue is used to perform the actual SPI transfer.

The blocking method is still available in case someone needs to perform
this operation synchronously (ie by calling led_set_brightness_sync()).

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@...phandler.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
---
 drivers/leds/leds-tlc5925.c | 38 +++++++++++++++++++++++++++++++++++--
 1 file changed, 36 insertions(+), 2 deletions(-)

diff --git a/drivers/leds/leds-tlc5925.c b/drivers/leds/leds-tlc5925.c
index 797836354c74..0423e3592bd7 100644
--- a/drivers/leds/leds-tlc5925.c
+++ b/drivers/leds/leds-tlc5925.c
@@ -18,6 +18,7 @@
 #include <linux/property.h>
 #include <linux/spi/spi.h>
 #include <linux/types.h>
+#include <linux/workqueue.h>
 
 #define TLC5925_SHIFT_REGISTER_LENGTH 16
 
@@ -29,10 +30,25 @@ struct single_led_priv {
 struct tlc5925_leds_priv {
 	int max_num_leds;
 	unsigned long *state;
+	struct spi_device *spi;
+	struct work_struct xmit_work;
 	struct single_led_priv leds[];
 };
 
-static int tlc5925_brightness_set_blocking(struct led_classdev *cdev,
+static int xmit(struct tlc5925_leds_priv *priv)
+{
+	return spi_write(priv->spi, priv->state, BITS_TO_BYTES(priv->max_num_leds));
+}
+
+static void xmit_work(struct work_struct *ws)
+{
+	struct tlc5925_leds_priv *priv =
+		container_of(ws, struct tlc5925_leds_priv, xmit_work);
+
+	xmit(priv);
+};
+
+static void tlc5925_brightness_set(struct led_classdev *cdev,
 					    enum led_brightness brightness)
 {
 	struct spi_device *spi = to_spi_device(cdev->dev->parent);
@@ -43,9 +59,23 @@ static int tlc5925_brightness_set_blocking(struct led_classdev *cdev,
 
 	assign_bit(index, priv->state, !!brightness);
 
-	return spi_write(spi, priv->state, BITS_TO_BYTES(priv->max_num_leds));
+	schedule_work(&priv->xmit_work);
 }
 
+static int tlc5925_brightness_set_blocking(struct led_classdev *cdev,
+					    enum led_brightness brightness)
+{
+	struct spi_device *spi = to_spi_device(cdev->dev->parent);
+	struct tlc5925_leds_priv *priv = spi_get_drvdata(spi);
+	struct single_led_priv *led =
+		container_of(cdev, struct single_led_priv, cdev);
+	int index = led->idx;
+
+	assign_bit(index, priv->state, !!brightness);
+
+	cancel_work_sync(&priv->xmit_work);
+	return xmit(priv);
+}
 static int tlc5925_probe(struct spi_device *spi)
 {
 	struct device *dev = &spi->dev;
@@ -83,6 +113,9 @@ static int tlc5925_probe(struct spi_device *spi)
 	if (!priv->state)
 		return -ENOMEM;
 
+	priv->spi = spi;
+	INIT_WORK(&priv->xmit_work, xmit_work);
+
 	priv->max_num_leds = max_num_leds;
 
 	device_for_each_child_node(dev, child) {
@@ -104,6 +137,7 @@ static int tlc5925_probe(struct spi_device *spi)
 		cdev = &(priv->leds[count].cdev);
 		cdev->brightness = LED_OFF;
 		cdev->max_brightness = 1;
+		cdev->brightness_set = tlc5925_brightness_set;
 		cdev->brightness_set_blocking = tlc5925_brightness_set_blocking;
 
 		ret = devm_led_classdev_register_ext(dev, cdev, &init_data);
-- 
2.25.1