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

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 <[email protected]>
---
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