Re: [PATCH v3 2/2] can: m_can: tcan4x5x: reset device before register access

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On 12/11/19 12:42 AM, Sean Nyekjaer wrote:
It's a good idea to reset a ip-block/spi device before using it,
this patch will reset the device.
And a generic reset function if needed elsewhere.

Signed-off-by: Sean Nyekjaer <sean@xxxxxxxxxx>
---
Changes since v2:
  - added reset function

  drivers/net/can/m_can/tcan4x5x.c | 16 ++++++++++++++--
  1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/net/can/m_can/tcan4x5x.c b/drivers/net/can/m_can/tcan4x5x.c
index 1f04fec7723d..b5d2ea0999c1 100644
--- a/drivers/net/can/m_can/tcan4x5x.c
+++ b/drivers/net/can/m_can/tcan4x5x.c
@@ -166,6 +166,18 @@ static void tcan4x5x_check_wake(struct tcan4x5x_priv *priv)
  	}
  }
+static void tcan4x5x_reset(struct tcan4x5x_priv *priv)
+{
+	if (priv->reset_gpio) {
+		gpiod_set_value(priv->reset_gpio, 1);
+
+		/* tpulse_width minimum 30us */
+		usleep_range(30, 100);
+		gpiod_set_value(priv->reset_gpio, 0);
+		usleep_range(700, 1000);
+	}

Do the software reset if GPIO is not valid then this will make sure the device is reset in either case.  Otherwise w/out the GPIO the device is not reset as the commit message indicates.  This is another reason for this function

} else {

    regmap_write(priv-regmap, TCAN4X5X_CONFIG, TCAN4X5X_SW_RESET);

}

Dan





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