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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Sean Nyekjaer <sean@geanix.com>,
        Marc Kleine-Budde <mkl@pengutronix.de>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 064/110] can: tcan4x5x: tcan4x5x_parse_config(): reset device before register access
Date:   Thu, 30 Jan 2020 19:38:40 +0100
Message-Id: <20200130183622.387523067@linuxfoundation.org>
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From: Sean Nyekjaer <sean@geanix.com>

[ Upstream commit c3083124e6a1c0d6cd4fe3b3f627b488bd3b10c4 ]

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@geanix.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/can/m_can/tcan4x5x.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/net/can/m_can/tcan4x5x.c b/drivers/net/can/m_can/tcan4x5x.c
index d797912e665a5..b233756345f83 100644
--- a/drivers/net/can/m_can/tcan4x5x.c
+++ b/drivers/net/can/m_can/tcan4x5x.c
@@ -164,6 +164,28 @@ static void tcan4x5x_check_wake(struct tcan4x5x_priv *priv)
 	}
 }
 
+static int tcan4x5x_reset(struct tcan4x5x_priv *priv)
+{
+	int ret = 0;
+
+	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);
+	} else {
+		ret = regmap_write(priv->regmap, TCAN4X5X_CONFIG,
+				   TCAN4X5X_SW_RESET);
+		if (ret)
+			return ret;
+	}
+
+	usleep_range(700, 1000);
+
+	return ret;
+}
+
 static int regmap_spi_gather_write(void *context, const void *reg,
 				   size_t reg_len, const void *val,
 				   size_t val_len)
@@ -341,6 +363,7 @@ static int tcan4x5x_init(struct m_can_classdev *cdev)
 static int tcan4x5x_parse_config(struct m_can_classdev *cdev)
 {
 	struct tcan4x5x_priv *tcan4x5x = cdev->device_data;
+	int ret;
 
 	tcan4x5x->device_wake_gpio = devm_gpiod_get(cdev->dev, "device-wake",
 						    GPIOD_OUT_HIGH);
@@ -354,7 +377,9 @@ static int tcan4x5x_parse_config(struct m_can_classdev *cdev)
 	if (IS_ERR(tcan4x5x->reset_gpio))
 		tcan4x5x->reset_gpio = NULL;
 
-	usleep_range(700, 1000);
+	ret = tcan4x5x_reset(tcan4x5x);
+	if (ret)
+		return ret;
 
 	tcan4x5x->device_state_gpio = devm_gpiod_get_optional(cdev->dev,
 							      "device-state",
-- 
2.20.1