linux-kernel - [PATCH] extcon: sm5502: Clear pending interrupts during initialization

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Message-Id: <20191008105434.119346-1-stephan@gerhold.net>
Date:   Tue,  8 Oct 2019 12:54:34 +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: Clear pending interrupts 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.

Reading the interrupt status registers twice seems to be sufficient
to make interrupts work in this situation.

Signed-off-by: Stephan Gerhold <stephan@...hold.net>
---
This makes interrupts work on the Samsung Galaxy A5 (2015), which
has recently gained mainline support [1].

I was not able to find a datasheet for SM5502, so this patch is
merely based on testing and comparison with the downstream driver [2].

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1329c1ab0730b521e6cd3051c56a2ff3d55f21e6
[2]: https://github.com/msm8916-mainline/android_kernel_qcom_msm8916/blob/SM-A500FU/drivers/misc/sm5502.c#L1566-L1578
---
 drivers/extcon/extcon-sm5502.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/extcon/extcon-sm5502.c b/drivers/extcon/extcon-sm5502.c
index dc43847ad2b0..c897f1aa4bf5 100644
--- a/drivers/extcon/extcon-sm5502.c
+++ b/drivers/extcon/extcon-sm5502.c
@@ -539,6 +539,12 @@ static void sm5502_init_dev_type(struct sm5502_muic_info *info)
 			val = info->reg_data[i].val;
 		regmap_write(info->regmap, info->reg_data[i].reg, val);
 	}
+
+	/* Clear pending interrupts */
+	regmap_read(info->regmap, SM5502_REG_INT1, &reg_data);
+	regmap_read(info->regmap, SM5502_REG_INT2, &reg_data);
+	regmap_read(info->regmap, SM5502_REG_INT1, &reg_data);
+	regmap_read(info->regmap, SM5502_REG_INT2, &reg_data);
 }

 static int sm5022_muic_i2c_probe(struct i2c_client *i2c,
-- 
2.23.0