[PATCH v3] can: tcan4x5x: put tcan into sleep when removing driver

[Sean Nyekjaer]

Put the tcan4x5x transceiver into sleep mode when the driver is
removed, instead of leaving it in its current operating mode.
This reduces power consumption(3mA@12V) once the driver is
no longer bound to the device.

Signed-off-by: Sean Nyekjaer <sean@xxxxxxxxxx>
---
Changes since v1:
 - Moved enter sleep mode into tcan4x5x_power_enable()

Changes since v2:
 - Added comment about RST pin
 - Fixed all calls to tcan4x5x_power_enable()

 drivers/net/can/m_can/tcan4x5x-core.c | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/drivers/net/can/m_can/tcan4x5x-core.c b/drivers/net/can/m_can/tcan4x5x-core.c
index 31cc9d0abd45..a318f1874b35 100644
--- a/drivers/net/can/m_can/tcan4x5x-core.c
+++ b/drivers/net/can/m_can/tcan4x5x-core.c
@@ -211,10 +211,26 @@ static int tcan4x5x_write_fifo(struct m_can_classdev *cdev,
 	return regmap_bulk_write(priv->regmap, TCAN4X5X_MRAM_START + addr_offset, val, val_count);
 }
 
-static int tcan4x5x_power_enable(struct regulator *reg, int enable)
+static int tcan4x5x_power_enable(struct tcan4x5x_priv *priv, int enable)
 {
-	if (IS_ERR_OR_NULL(reg))
+	struct regulator *reg = priv->power;
+
+	/*
+	 * Check if the power regulator is configured. If it is, just power
+	 * the device on/off. If not, put the device into sleep mode here if
+	 * the RST pin is available, since a wake-up event, RST pin toggle,
+	 * or power cycle are the only ways to exit sleep mode.
+	 * Datasheet: TCAN4550, section "8.4.3 Sleep Mode"
+	 * https://www.ti.com/lit/gpn/tcan4550
+	 */
+	if (IS_ERR_OR_NULL(reg)) {
+		if (priv->reset_gpio && !enable)
+			return regmap_update_bits(priv->regmap, TCAN4X5X_CONFIG,
+						  TCAN4X5X_MODE_SEL_MASK,
+						  TCAN4X5X_MODE_SLEEP);
+
 		return 0;
+	}
 
 	if (enable)
 		return regulator_enable(reg);
@@ -476,7 +492,7 @@ static int tcan4x5x_can_probe(struct spi_device *spi)
 		goto out_m_can_class_free_dev;
 	}
 
-	ret = tcan4x5x_power_enable(priv->power, 1);
+	ret = tcan4x5x_power_enable(priv, 1);
 	if (ret) {
 		dev_err(&spi->dev, "Enabling regulator failed %pe\n",
 			ERR_PTR(ret));
@@ -531,7 +547,7 @@ static int tcan4x5x_can_probe(struct spi_device *spi)
 	return 0;
 
 out_power:
-	tcan4x5x_power_enable(priv->power, 0);
+	tcan4x5x_power_enable(priv, 0);
  out_m_can_class_free_dev:
 	m_can_class_free_dev(mcan_class->net);
 	return ret;
@@ -543,7 +559,7 @@ static void tcan4x5x_can_remove(struct spi_device *spi)
 
 	m_can_class_unregister(&priv->cdev);
 
-	tcan4x5x_power_enable(priv->power, 0);
+	tcan4x5x_power_enable(priv, 0);
 
 	m_can_class_free_dev(priv->cdev.net);
 }
-- 
2.55.0