linux-kernel - [PATCH] extcon: sm5502: Reset registers during initialization

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Date:   Thu, 10 Oct 2019 17:47:20 +0200
From:   Stephan Gerhold <stephan@...hold.net>
To:     Chanwoo Choi <cw00.choi@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>
Cc:     linux-kernel@...r.kernel.org, Stephan Gerhold <stephan@...hold.net>
Subject: [PATCH] extcon: sm5502: Reset registers during initialization

On some devices (e.g. Samsung Galaxy A5 (2015)), the bootloader
seems to keep interrupts enabled for SM5502 when booting Linux.
Changing the cable state (i.e. plugging in a cable) - until the driver
is loaded - will therefore produce an interrupt that is never read.

In this situation, the cable state will be stuck forever on the
initial state because SM5502 stops sending interrupts.
This can be avoided by clearing those pending interrupts after
the driver has been loaded.

One way to do this is to reset all registers to default state
by writing to SM5502_REG_RESET. This ensures that we start from
a clean state, with all interrupts disabled.

Suggested-by: Chanwoo Choi <cw00.choi@...sung.com>
Signed-off-by: Stephan Gerhold <stephan@...hold.net>
---
 drivers/extcon/extcon-sm5502.c | 4 ++++
 drivers/extcon/extcon-sm5502.h | 2 ++
 2 files changed, 6 insertions(+)

diff --git a/drivers/extcon/extcon-sm5502.c b/drivers/extcon/extcon-sm5502.c
index dc43847ad2b0..b3d93baf4fc5 100644
--- a/drivers/extcon/extcon-sm5502.c
+++ b/drivers/extcon/extcon-sm5502.c
@@ -65,6 +65,10 @@ struct sm5502_muic_info {
 /* Default value of SM5502 register to bring up MUIC device. */
 static struct reg_data sm5502_reg_data[] = {
 	{
+		.reg = SM5502_REG_RESET,
+		.val = SM5502_REG_RESET_MASK,
+		.invert = true,
+	}, {
 		.reg = SM5502_REG_CONTROL,
 		.val = SM5502_REG_CONTROL_MASK_INT_MASK,
 		.invert = false,
diff --git a/drivers/extcon/extcon-sm5502.h b/drivers/extcon/extcon-sm5502.h
index 9dbb634d213b..ce1f1ec310c4 100644
--- a/drivers/extcon/extcon-sm5502.h
+++ b/drivers/extcon/extcon-sm5502.h
@@ -237,6 +237,8 @@ enum sm5502_reg {
 #define DM_DP_SWITCH_UART			((DM_DP_CON_SWITCH_UART <<SM5502_REG_MANUAL_SW1_DP_SHIFT) \
 						| (DM_DP_CON_SWITCH_UART <<SM5502_REG_MANUAL_SW1_DM_SHIFT))
 
+#define SM5502_REG_RESET_MASK			(0x1)
+
 /* SM5502 Interrupts */
 enum sm5502_irq {
 	/* INT1 */
-- 
2.23.0