linux-kernel - [PATCH v3 1/2] mfd: da9062: enable being a system-power-controller

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Message-ID: <bafccf43111a24e20fb36c46740d650dedda04c0.1656418366.git.helmut.grohne@intenta.de>
Date:   Tue, 28 Jun 2022 14:45:21 +0200
From:   Helmut Grohne <helmut.grohne@...enta.de>
To:     Support Opensource <support.opensource@...semi.com>,
        Lee Jones <lee.jones@...aro.org>
CC:     <linux-kernel@...r.kernel.org>,
        Adam Thomson <Adam.Thomson.Opensource@...semi.com>,
        Mark Brown <broonie@...nel.org>,
        Wolfram Sang <wsa@...-dreams.de>
Subject: [PATCH v3 1/2] mfd: da9062: enable being a system-power-controller

The DA9062 can be the device used to power the CPU. In that case, it can
be used to power off the system. In the CONTROL_A register, the M_*_EN
bits must be zero for the corresponding *_EN bits to have an effect. We
zero them all to turn off the system.

Signed-off-by: Helmut Grohne <helmut.grohne@...enta.de>
---
 drivers/mfd/da9062-core.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

Compared to v2, this addresses the following concerns raised by Lee Jones:
 * Drop unnecessary comment.
 * Restructure da9062_power_off to avoid unnecessary assignments.
 * Make power off failure message user friendly while still including
   the error code for diagnostics.

Lee Jones also questioned the utility of warning about pm_power_off already
being assigned:

> Do we really mind/care?
>
> Is there anything we can do about it?
>
> Thus, do we really need to warn() about it?

I do think this is useful, because it only happens when two nodes decalare
being a system-power-controller. It is a misconfiguration of your device tree
that is being warned here. Other drivers (e.g. rn5t618.c, act8865-regulator.c,
rtc-jz4740.c, and bcm2835_wdt.c) issue a similar warning.

I note that Adam Thomson reviewed v2. Thank you. I did not include the
Reviewed-by, because noticeable code changed compared to what was reviewed.

As pointed out by Adam Thomson, this version still uses regmap (and possibly
mutexes) in pm_power_off (with irqs disabled). This is a fundamental problem
shared with many other pm_power_off hooks.

I've now included Rob Herring's Acked-by on the second patch as the rebase was
trivial.

Helmut
diff --git a/drivers/mfd/da9062-core.c b/drivers/mfd/da9062-core.c
index 2774b2cbaea6..0083a2756f28 100644
--- a/drivers/mfd/da9062-core.c
+++ b/drivers/mfd/da9062-core.c
@@ -620,6 +620,26 @@ static const struct of_device_id da9062_dt_ids[] = {
 };
 MODULE_DEVICE_TABLE(of, da9062_dt_ids);

+static struct i2c_client *da9062_i2c_client;
+
+static void da9062_power_off(void)
+{
+	int ret;
+
+	ret = regmap_update_bits(
+		((struct da9062*)i2c_get_clientdata(da9062_i2c_client))->regmap,
+		DA9062AA_CONTROL_A,
+		DA9062AA_SYSTEM_EN_MASK | DA9062AA_POWER_EN_MASK |
+			DA9062AA_POWER1_EN_MASK | DA9062AA_M_SYSTEM_EN_MASK |
+			DA9062AA_M_POWER_EN_MASK | DA9062AA_M_POWER1_EN_MASK,
+		0
+	);
+
+	if (ret < 0)
+		dev_err(&da9062_i2c_client->dev,
+			"failed to power the system off (err=%d)\n", ret);
+}
+
 static int da9062_i2c_probe(struct i2c_client *i2c,
 	const struct i2c_device_id *id)
 {
@@ -720,6 +740,15 @@ static int da9062_i2c_probe(struct i2c_client *i2c,
 		return ret;
 	}

+	if (of_device_is_system_power_controller(i2c->dev.of_node)) {
+		if (!pm_power_off) {
+			da9062_i2c_client = i2c;
+			pm_power_off = da9062_power_off;
+		} else {
+			dev_warn(&i2c->dev, "Poweroff callback already assigned\n");
+		}
+	}
+
 	return ret;
 }

@@ -727,6 +756,11 @@ static int da9062_i2c_remove(struct i2c_client *i2c)
 {
 	struct da9062 *chip = i2c_get_clientdata(i2c);

+	if (pm_power_off == da9062_power_off)
+		pm_power_off = NULL;
+	if (da9062_i2c_client)
+		da9062_i2c_client = NULL;
+
 	mfd_remove_devices(chip->dev);
 	regmap_del_irq_chip(i2c->irq, chip->regmap_irq);

-- 
2.30.2

Dipl.-Inf. Helmut Grohne
Research and Development
Application Engineering

Phone: +49 (371) 24354 0 ∙ Fax:  +49 (371) 24354 020
helmut.grohne@...enta.de ∙ https://www.intenta.de

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