diff mbox series

[4/4] extcon: max8997: Avoid forcing UART path on drive probe

Message ID 20181108134548.31140-5-m.szyprowski@samsung.com (mailing list archive)
State Accepted
Commit 3e34c819896091d0f1bbf6ece8a620552f8dc04e
Headers show
Series Fix common issue in MAX* extcon drivers | expand

Commit Message

Marek Szyprowski Nov. 8, 2018, 1:45 p.m. UTC
Driver unconditionally forces UART path during probe, probably to ensure
that one can get kernel serial log as soon as possible.

This approach causes some issues, especially when board is booted with
non-UART cable connected to micro-USB port. For example, when USB cable is
connected, UART TX/RX lines are unconditionally short-circuited to USB
D+/D- lines. This is in turn recognized by a series of serial BREAK
signals and some random characters when USB host tries to perform
enumeration procedure.

To solve the above issue and keep UART console operational as early as
possible, set UART path only when USB ID reports UART capable cable.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 drivers/extcon/extcon-max8997.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/drivers/extcon/extcon-max8997.c b/drivers/extcon/extcon-max8997.c
index bdabb2479e0d..632192d027bf 100644
--- a/drivers/extcon/extcon-max8997.c
+++ b/drivers/extcon/extcon-max8997.c
@@ -632,6 +632,8 @@  static int max8997_muic_probe(struct platform_device *pdev)
 	struct max8997_platform_data *pdata = dev_get_platdata(max8997->dev);
 	struct max8997_muic_info *info;
 	int delay_jiffies;
+	int cable_type;
+	bool attached;
 	int ret, i;
 
 	info = devm_kzalloc(&pdev->dev, sizeof(struct max8997_muic_info),
@@ -724,8 +726,17 @@  static int max8997_muic_probe(struct platform_device *pdev)
 		delay_jiffies = msecs_to_jiffies(DELAY_MS_DEFAULT);
 	}
 
-	/* Set initial path for UART */
-	 max8997_muic_set_path(info, info->path_uart, true);
+	/* Set initial path for UART when JIG is connected to get serial logs */
+	ret = max8997_bulk_read(info->muic, MAX8997_MUIC_REG_STATUS1,
+				2, info->status);
+	if (ret) {
+		dev_err(info->dev, "failed to read MUIC register\n");
+		return ret;
+	}
+	cable_type = max8997_muic_get_cable_type(info,
+					   MAX8997_CABLE_GROUP_ADC, &attached);
+	if (attached && cable_type == MAX8997_MUIC_ADC_FACTORY_MODE_UART_OFF)
+		max8997_muic_set_path(info, info->path_uart, true);
 
 	/* Set ADC debounce time */
 	max8997_muic_set_debounce_time(info, ADC_DEBOUNCE_TIME_25MS);