linux-kernel - [PATCH] regulator: wm8994: Add an off-on delay for WM8994 variant

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Date:   Sun, 27 Mar 2022 15:15:53 -0700
From:   Jonathan Bakker <xc-racer2@...e.ca>
To:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>
Cc:     patches@...nsource.cirrus.com, linux-kernel@...r.kernel.org,
        Jonathan Bakker <xc-racer2@...e.ca>
Subject: [PATCH] regulator: wm8994: Add an off-on delay for WM8994 variant

As per Table 130 of the wm8994 datasheet at [1], there is an off-on
delay for LDO1 and LDO2.  In the wm8958 datasheet [2], I could not
find any reference to it.  I could not find a wm1811 datasheet to
double-check there, but as no one has complained presumably it works
without it.

This solves the issue on Samsung Aries boards with a wm8994 where
register writes fail when the device is powered off and back-on
quickly.

[1] https://statics.cirrus.com/pubs/proDatasheet/WM8994_Rev4.6.pdf
[2] https://statics.cirrus.com/pubs/proDatasheet/WM8958_v3.5.pdf

Signed-off-by: Jonathan Bakker <xc-racer2@...e.ca>
---
 drivers/regulator/wm8994-regulator.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/regulator/wm8994-regulator.c b/drivers/regulator/wm8994-regulator.c
index cadea0344486..135fdf3f9fdd 100644
--- a/drivers/regulator/wm8994-regulator.c
+++ b/drivers/regulator/wm8994-regulator.c
@@ -70,7 +70,7 @@ static const struct regulator_ops wm8994_ldo2_ops = {
 	.set_voltage_sel = regulator_set_voltage_sel_regmap,
 };
 
-static const struct regulator_desc wm8994_ldo_desc[] = {
+static struct regulator_desc wm8994_ldo_desc[] = {
 	{
 		.name = "LDO1",
 		.id = 1,
@@ -167,6 +167,10 @@ static int wm8994_ldo_probe(struct platform_device *pdev)
 		ldo->init_data = *pdata->ldo[id].init_data;
 	}
 
+	/* WM8994 requires an off-on delay while others do not */
+	if (ldo->wm8994->type == WM8994)
+		wm8994_ldo_desc[id].off_on_delay = 36000;
+
 	/*
 	 * At this point the GPIO descriptor is handled over to the
 	 * regulator core and we need not worry about it on the
-- 
2.20.1