platform: arm64: thinkpad-t14s-ec: add system PM hooks

Improve support for system suspend. The register information has been
extracted from the ACPI DSDT code handling Windows Modern Standby. I
took over the weird multi-write function from the ACPI DSDT code where
it is called ECWS.

In addition to writing to the 0xE0 register, the ACPI Windows Modern
Standby code also does some changes to the thermal configuration. This
part is not implemented.

After this patch the laptop's power and LID LEDs will switch into the
typical breathing animation when the system is suspended and enabled
normally again after resuming.

Signed-off-by: Sebastian Reichel <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Reviewed-by: Ilpo Järvinen <[e-mail]>
Signed-off-by: Ilpo Järvinen <[e-mail]>

drivers/platform/arm64/lenovo-thinkpad-t14s.c

···
 #include <linux/module.h>
 #include <linux/regmap.h>
 #include <linux/slab.h>
+#include <linux/pm.h>
 
 #define T14S_EC_CMD_ECRD	0x02
 #define T14S_EC_CMD_ECWR	0x03
 #define T14S_EC_CMD_EVT		0xf0
 
-#define T14S_EC_REG_LED		0x0c
-#define T14S_EC_REG_KBD_BL1	0x0d
-#define T14S_EC_REG_KBD_BL2	0xe1
-#define T14S_EC_KBD_BL1_MASK	GENMASK_U8(7, 6)
-#define T14S_EC_KBD_BL2_MASK	GENMASK_U8(3, 2)
-#define T14S_EC_REG_AUD		0x30
-#define T14S_EC_MIC_MUTE_LED	BIT(5)
-#define T14S_EC_SPK_MUTE_LED	BIT(6)
+#define T14S_EC_REG_LED				0x0c
+#define T14S_EC_REG_KBD_BL1			0x0d
+#define T14S_EC_REG_MODERN_STANDBY		0xe0
+#define T14S_EC_MODERN_STANDBY_ENTRY		BIT(1)
+#define T14S_EC_MODERN_STANDBY_EXIT		BIT(0)
+#define T14S_EC_REG_KBD_BL2			0xe1
+#define T14S_EC_KBD_BL1_MASK			GENMASK_U8(7, 6)
+#define T14S_EC_KBD_BL2_MASK			GENMASK_U8(3, 2)
+#define T14S_EC_REG_AUD				0x30
+#define T14S_EC_MIC_MUTE_LED			BIT(5)
+#define T14S_EC_SPK_MUTE_LED			BIT(6)
 
 #define T14S_EC_EVT_NONE			0x00
 #define T14S_EC_EVT_KEY_FN_4			0x13
···
 out:
 	i2c_unlock_bus(client->adapter, I2C_LOCK_SEGMENT);
 	return ret;
+}
+
+static void t14s_ec_write_sequence(struct t14s_ec *ec, u8 reg, u8 val, u8 cnt)
+{
+	int i;
+
+	for (i = 0; i < cnt; i++)
+		regmap_write(ec->regmap, reg, val);
 }
 
 static int t14s_led_set_status(struct t14s_ec *ec,
···
 		return -ENOMEM;
 
 	ec->dev = dev;
+	i2c_set_clientdata(client, ec);
 
 	ec->regmap = devm_regmap_init(dev, &t14s_ec_regmap_bus,
 				      ec, &t14s_ec_regmap_config);
···
 	return 0;
 }
 
+static int t14s_ec_suspend(struct device *dev)
+{
+	struct t14s_ec *ec = dev_get_drvdata(dev);
+
+	t14s_ec_write_sequence(ec, T14S_EC_REG_MODERN_STANDBY,
+			       T14S_EC_MODERN_STANDBY_ENTRY, 3);
+
+	return 0;
+}
+
+static int t14s_ec_resume(struct device *dev)
+{
+	struct t14s_ec *ec = dev_get_drvdata(dev);
+
+	t14s_ec_write_sequence(ec, T14S_EC_REG_MODERN_STANDBY,
+			       T14S_EC_MODERN_STANDBY_EXIT, 3);
+
+	return 0;
+}
+
 static const struct of_device_id t14s_ec_of_match[] = {
 	{ .compatible = "lenovo,thinkpad-t14s-ec" },
 	{}
···
 };
 MODULE_DEVICE_TABLE(i2c, t14s_ec_i2c_id_table);
 
+static const struct dev_pm_ops t14s_ec_pm_ops = {
+	SYSTEM_SLEEP_PM_OPS(t14s_ec_suspend, t14s_ec_resume)
+};
+
 static struct i2c_driver t14s_ec_i2c_driver = {
 	.driver = {
 		.name = "thinkpad-t14s-ec",
 		.of_match_table = t14s_ec_of_match,
+		.pm = &t14s_ec_pm_ops,
 	},
 	.probe = t14s_ec_probe,
 	.id_table = t14s_ec_i2c_id_table,