[PATCH 7/8] iio: light: cm32181: Add support for parsing CPM0 and CPM1 ACPI tables

[Hans de Goede <hdegoede@redhat.com>]

On ACPI based systems the CPLM3218 ACPI device node describing the
CM3218[1] sensor typically will have some extra tables with register
init values for initializing the sensor and calibration info.

This is based on a newer version of cm32181.c, with a copyright of:

 * Copyright (C) 2014 Capella Microsystems Inc.
 * Author: Kevin Tsai <ktsai@capellamicro.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2, as published
 * by the Free Software Foundation.

Which is floating around on the net in various places, but the changes
from this newer version never made it upstream.

This was tested on the following models: Acer Switch 10 SW5-012 (CM32181)
Asus T100TA (CM3218), Asus T100CHI (CM3218) and HP X2 10-n000nd (CM32181).

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/iio/light/cm32181.c | 98 +++++++++++++++++++++++++++++++++++++
 1 file changed, 98 insertions(+)

diff --git a/drivers/iio/light/cm32181.c b/drivers/iio/light/cm32181.c
index e5674d4a8143..878fc13632d8 100644
--- a/drivers/iio/light/cm32181.c
+++ b/drivers/iio/light/cm32181.c
@@ -4,6 +4,7 @@
  * Author: Kevin Tsai <ktsai@capellamicro.com>
  */
 
+#include <linux/acpi.h>
 #include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/i2c.h>
@@ -53,6 +54,15 @@
 
 #define SMBUS_ALERT_RESPONSE_ADDRESS	0x0c
 
+/* CPM0 Index 0: device-id (3218 or 32181), 1: Unknown, 2: init_regs_bitmap */
+#define CPM0_REGS_BITMAP		2
+#define CPM0_HEADER_SIZE		3
+
+/* CPM1 Index 0: lux_per_bit, 1: calibscale, 2: resolution (100000) */
+#define CPM1_LUX_PER_BIT		0
+#define CPM1_CALIBSCALE			1
+#define CPM1_SIZE			3
+
 /* CM3218 Family */
 static const int cm3218_als_it_bits[] = { 0, 1, 2, 3 };
 static const int cm3218_als_it_values[] = { 100000, 200000, 400000, 800000 };
@@ -76,6 +86,56 @@ struct cm32181_chip {
 	const int *als_it_values;
 };
 
+static int cm32181_read_als_it(struct cm32181_chip *cm32181, int *val2);
+
+#ifdef CONFIG_ACPI
+/**
+ * cm32181_acpi_get_cpm() - Get CPM object from ACPI
+ * @client	pointer of struct i2c_client.
+ * @obj_name	pointer of ACPI object name.
+ * @count	maximum size of return array.
+ * @vals	pointer of array for return elements.
+ *
+ * Convert ACPI CPM table to array.
+ *
+ * Return: -ENODEV for fail.  Otherwise is number of elements.
+ */
+static int cm32181_acpi_get_cpm(struct i2c_client *client, char *obj_name,
+				u64 *values, int count)
+{
+	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+	union acpi_object *cpm, *elem;
+	acpi_handle handle;
+	acpi_status status;
+	int i;
+
+	handle = ACPI_HANDLE(&client->dev);
+	if (!handle)
+		return -ENODEV;
+
+	status = acpi_evaluate_object(handle, obj_name, NULL, &buffer);
+	if (ACPI_FAILURE(status)) {
+		dev_err(&client->dev, "object %s not found\n", obj_name);
+		return -ENODEV;
+	}
+
+	cpm = buffer.pointer;
+	if (cpm->package.count > count)
+		dev_warn(&client->dev, "%s table contains %d values, only using first %d values\n",
+			 obj_name, cpm->package.count, count);
+
+	count = min_t(int, cpm->package.count, count);
+	for (i = 0; i < count; i++) {
+		elem = &(cpm->package.elements[i]);
+		values[i] = elem->integer.value;
+	}
+
+	kfree(buffer.pointer);
+
+	return count;
+}
+#endif /* CONFIG_ACPI */
+
 /**
  * cm32181_reg_init() - Initialize CM32181 registers
  * @cm32181:	pointer of struct cm32181.
@@ -121,6 +181,44 @@ static int cm32181_reg_init(struct cm32181_chip *cm32181)
 	cm32181->lux_per_bit = CM32181_LUX_PER_BIT;
 	cm32181->lux_per_bit_base_it = CM32181_LUX_PER_BIT_BASE_IT;
 
+#ifdef CONFIG_ACPI
+	if (ACPI_HANDLE(&client->dev)) {
+		u64 values[CPM0_HEADER_SIZE + CM32181_CONF_REG_NUM];
+		int count;
+
+		count = cm32181_acpi_get_cpm(client, "CPM0",
+					     values, ARRAY_SIZE(values));
+		if (count <= CPM0_HEADER_SIZE)
+			goto cpm_parsing_done;
+
+		count -= CPM0_HEADER_SIZE;
+
+		cm32181->init_regs_bitmap = values[CPM0_REGS_BITMAP];
+		cm32181->init_regs_bitmap &= GENMASK(count - 1, 0);
+		for (i = 0; i < count; i++) {
+			if (cm32181->init_regs_bitmap & BIT(i))
+				cm32181->conf_regs[i] =
+					values[CPM0_HEADER_SIZE + i];
+		}
+
+		count = cm32181_acpi_get_cpm(client, "CPM1",
+					     values, ARRAY_SIZE(values));
+		if (count != CPM1_SIZE)
+			goto cpm_parsing_done;
+
+		cm32181->lux_per_bit = values[CPM1_LUX_PER_BIT];
+
+		/* Check for uncalibrated devices */
+		if (values[CPM1_CALIBSCALE] == CM32181_CALIBSCALE_DEFAULT)
+			goto cpm_parsing_done;
+
+		cm32181->calibscale  = values[CPM1_CALIBSCALE];
+		/* CPM1 lux_per_bit is for the current it value */
+		cm32181_read_als_it(cm32181, &cm32181->lux_per_bit_base_it);
+	}
+cpm_parsing_done:
+#endif /* CONFIG_ACPI */
+
 	/* Initialize registers*/
 	for (i = 0; i < CM32181_CONF_REG_NUM; i++) {
 		if (cm32181->init_regs_bitmap & BIT(i)) {
-- 
2.26.0