platform/x86: x86-android-tablets: New driver for x86 Android tablets

x86 tablets which ship with Android as (part of) the factory image
typically have various problems with their DSDTs. The factory kernels
shipped on these devices typically have device addresses and GPIOs
hardcoded in the kernel, rather then specified in their DSDT.

With the DSDT containing a random collection of devices which may or
may not actually be present as well as missing devices which are
actually present.

This driver, which loads only on affected models based on DMI matching,
adds DMI based instantiating of kernel devices for devices which are
missing from the DSDT, fixing e.g. battery monitoring, touchpads and/or
accelerometers not working.

Note the Kconfig help text also refers to "various fixes" ATM there are
no such fixes, but there are also known cases where entries are present
in the DSDT but they contain bugs, such as missing/wrong GPIOs. The plan
is to also add fixes for things like this here in the future.

This is the least ugly option to get these devices to fully work and to
do so without adding any extra code to the main kernel image (vmlinuz)
when built as a module.

Link: https://lore.kernel.org/platform-driver-x86/20211031162428.22368-1-hdegoede@redhat.com/Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20211223190750.397487-1-hdegoede@redhat.com

MAINTAINERS

@@ -20667,6 +20667,13 @@ S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/mm
 F:	arch/x86/mm/
 
+X86 PLATFORM ANDROID TABLETS DSDT FIXUP DRIVER
+M:	Hans de Goede <hdegoede@redhat.com>
+L:	platform-driver-x86@vger.kernel.org
+S:	Maintained
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git
+F:	drivers/platform/x86/x86-android-tablets.c
+
 X86 PLATFORM DRIVERS
 M:	Hans de Goede <hdegoede@redhat.com>
 M:	Mark Gross <markgross@kernel.org>

drivers/platform/x86/Kconfig

@@ -1004,6 +1004,23 @@ config TOUCHSCREEN_DMI
 	  the OS-image for the device. This option supplies the missing info.
 	  Enable this for x86 tablets with Silead or Chipone touchscreens.
 
+config X86_ANDROID_TABLETS
+	tristate "X86 Android tablet support"
+	depends on I2C && ACPI && GPIOLIB
+	help
+	  X86 tablets which ship with Android as (part of) the factory image
+	  typically have various problems with their DSDTs. The factory kernels
+	  shipped on these devices typically have device addresses and GPIOs
+	  hardcoded in the kernel, rather than specified in their DSDT.
+
+	  With the DSDT containing a random collection of devices which may or
+	  may not actually be present. This driver contains various fixes for
+	  such tablets, including instantiating kernel devices for devices which
+	  are missing from the DSDT.
+
+	  If you have a x86 Android tablet say Y or M here, for a generic x86
+	  distro config say M here.
+
 config FW_ATTR_CLASS
 	tristate
 

drivers/platform/x86/Makefile

@@ -113,6 +113,7 @@ obj-$(CONFIG_I2C_MULTI_INSTANTIATE)	+= i2c-multi-instantiate.o
 obj-$(CONFIG_MLX_PLATFORM)		+= mlx-platform.o
 obj-$(CONFIG_TOUCHSCREEN_DMI)		+= touchscreen_dmi.o
 obj-$(CONFIG_WIRELESS_HOTKEY)		+= wireless-hotkey.o
+obj-$(CONFIG_X86_ANDROID_TABLETS)	+= x86-android-tablets.o
 
 # Intel uncore drivers
 obj-$(CONFIG_INTEL_IPS)				+= intel_ips.o

drivers/platform/x86/x86-android-tablets.c

+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * DMI based code to deal with broken DSDTs on X86 tablets which ship with
+ * Android as (part of) the factory image. The factory kernels shipped on these
+ * devices typically have a bunch of things hardcoded, rather than specified
+ * in their DSDT.
+ *
+ * Copyright (C) 2021 Hans de Goede <hdegoede@redhat.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/acpi.h>
+#include <linux/dmi.h>
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/driver.h>
+#include <linux/gpio/machine.h>
+#include <linux/i2c.h>
+#include <linux/irq.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/string.h>
+/* For gpio_get_desc() which is EXPORT_SYMBOL_GPL() */
+#include "../../gpio/gpiolib.h"
+
+/*
+ * Helper code to get Linux IRQ numbers given a description of the IRQ source
+ * (either IOAPIC index, or GPIO chip name + pin-number).
+ */
+enum x86_acpi_irq_type {
+	X86_ACPI_IRQ_TYPE_NONE,
+	X86_ACPI_IRQ_TYPE_APIC,
+	X86_ACPI_IRQ_TYPE_GPIOINT,
+};
+
+struct x86_acpi_irq_data {
+	char *chip;   /* GPIO chip label (GPIOINT) */
+	enum x86_acpi_irq_type type;
+	int index;
+	int trigger;  /* ACPI_EDGE_SENSITIVE / ACPI_LEVEL_SENSITIVE */
+	int polarity; /* ACPI_ACTIVE_HIGH / ACPI_ACTIVE_LOW / ACPI_ACTIVE_BOTH */
+};
+
+static int x86_acpi_irq_helper_gpiochip_find(struct gpio_chip *gc, void *data)
+{
+	return gc->label && !strcmp(gc->label, data);
+}
+
+static int x86_acpi_irq_helper_get(const struct x86_acpi_irq_data *data)
+{
+	struct gpio_desc *gpiod;
+	struct gpio_chip *chip;
+	unsigned int irq_type;
+	int irq, ret;
+
+	switch (data->type) {
+	case X86_ACPI_IRQ_TYPE_APIC:
+		irq = acpi_register_gsi(NULL, data->index, data->trigger, data->polarity);
+		if (irq < 0)
+			pr_err("error %d getting APIC IRQ %d\n", irq, data->index);
+
+		return irq;
+	case X86_ACPI_IRQ_TYPE_GPIOINT:
+		/* Like acpi_dev_gpio_irq_get(), but without parsing ACPI resources */
+		chip = gpiochip_find(data->chip, x86_acpi_irq_helper_gpiochip_find);
+		if (!chip)
+			return -EPROBE_DEFER;
+
+		gpiod = gpiochip_get_desc(chip, data->index);
+		if (IS_ERR(gpiod)) {
+			ret = PTR_ERR(gpiod);
+			pr_err("error %d getting GPIO %s %d\n", ret, data->chip, data->index);
+			return ret;
+		}
+
+		irq = gpiod_to_irq(gpiod);
+		if (irq < 0) {
+			pr_err("error %d getting IRQ %s %d\n", irq, data->chip, data->index);
+			return irq;
+		}
+
+		irq_type = acpi_dev_get_irq_type(data->trigger, data->polarity);
+		if (irq_type != IRQ_TYPE_NONE && irq_type != irq_get_trigger_type(irq))
+			irq_set_irq_type(irq, irq_type);
+
+		return irq;
+	default:
+		return 0;
+	}
+}
+
+struct x86_i2c_client_info {
+	struct i2c_board_info board_info;
+	char *adapter_path;
+	struct x86_acpi_irq_data irq_data;
+};
+
+struct x86_dev_info {
+	const struct x86_i2c_client_info *i2c_client_info;
+	int i2c_client_count;
+};
+
+/*
+ * When booted with the BIOS set to Android mode the Chuwi Hi8 (CWI509) DSDT
+ * contains a whole bunch of bogus ACPI I2C devices and is missing entries
+ * for the touchscreen and the accelerometer.
+ */
+static const struct property_entry chuwi_hi8_gsl1680_props[] = {
+	PROPERTY_ENTRY_U32("touchscreen-size-x", 1665),
+	PROPERTY_ENTRY_U32("touchscreen-size-y", 1140),
+	PROPERTY_ENTRY_BOOL("touchscreen-swapped-x-y"),
+	PROPERTY_ENTRY_BOOL("silead,home-button"),
+	PROPERTY_ENTRY_STRING("firmware-name", "gsl1680-chuwi-hi8.fw"),
+	{ }
+};
+
+static const struct software_node chuwi_hi8_gsl1680_node = {
+	.properties = chuwi_hi8_gsl1680_props,
+};
+
+static const char * const chuwi_hi8_mount_matrix[] = {
+	"1", "0", "0",
+	"0", "-1", "0",
+	"0", "0", "1"
+};
+
+static const struct property_entry chuwi_hi8_bma250e_props[] = {
+	PROPERTY_ENTRY_STRING_ARRAY("mount-matrix", chuwi_hi8_mount_matrix),
+	{ }
+};
+
+static const struct software_node chuwi_hi8_bma250e_node = {
+	.properties = chuwi_hi8_bma250e_props,
+};
+
+static const struct x86_i2c_client_info chuwi_hi8_i2c_clients[] __initconst = {
+	{
+		/* Silead touchscreen */
+		.board_info = {
+			.type = "gsl1680",
+			.addr = 0x40,
+			.swnode = &chuwi_hi8_gsl1680_node,
+		},
+		.adapter_path = "\\_SB_.I2C4",
+		.irq_data = {
+			.type = X86_ACPI_IRQ_TYPE_APIC,
+			.index = 0x44,
+			.trigger = ACPI_EDGE_SENSITIVE,
+			.polarity = ACPI_ACTIVE_HIGH,
+		},
+	}, {
+		/* BMA250E accelerometer */
+		.board_info = {
+			.type = "bma250e",
+			.addr = 0x18,
+			.swnode = &chuwi_hi8_bma250e_node,
+		},
+		.adapter_path = "\\_SB_.I2C3",
+		.irq_data = {
+			.type = X86_ACPI_IRQ_TYPE_GPIOINT,
+			.chip = "INT33FC:02",
+			.index = 23,
+			.trigger = ACPI_LEVEL_SENSITIVE,
+			.polarity = ACPI_ACTIVE_HIGH,
+		},
+	},
+};
+
+static const struct x86_dev_info chuwi_hi8_info __initconst = {
+	.i2c_client_info = chuwi_hi8_i2c_clients,
+	.i2c_client_count = ARRAY_SIZE(chuwi_hi8_i2c_clients),
+};
+
+/*
+ * If the EFI bootloader is not Xiaomi's own signed Android loader, then the
+ * Xiaomi Mi Pad 2 X86 tablet sets OSID in the DSDT to 1 (Windows), causing
+ * a bunch of devices to be hidden.
+ *
+ * This takes care of instantiating the hidden devices manually.
+ */
+static const char * const bq27520_suppliers[] = { "bq25890-charger" };
+
+static const struct property_entry bq27520_props[] = {
+	PROPERTY_ENTRY_STRING_ARRAY("supplied-from", bq27520_suppliers),
+	{ }
+};
+
+static const struct software_node bq27520_node = {
+	.properties = bq27520_props,
+};
+
+static const struct x86_i2c_client_info xiaomi_mipad2_i2c_clients[] __initconst = {
+	{
+		/* BQ27520 fuel-gauge */
+		.board_info = {
+			.type = "bq27520",
+			.addr = 0x55,
+			.dev_name = "bq27520",
+			.swnode = &bq27520_node,
+		},
+		.adapter_path = "\\_SB_.PCI0.I2C1",
+	}, {
+		/* KTD2026 RGB notification LED controller */
+		.board_info = {
+			.type = "ktd2026",
+			.addr = 0x30,
+			.dev_name = "ktd2026",
+		},
+		.adapter_path = "\\_SB_.PCI0.I2C3",
+	},
+};
+
+static const struct x86_dev_info xiaomi_mipad2_info __initconst = {
+	.i2c_client_info = xiaomi_mipad2_i2c_clients,
+	.i2c_client_count = ARRAY_SIZE(xiaomi_mipad2_i2c_clients),
+};
+
+static const struct dmi_system_id x86_android_tablet_ids[] __initconst = {
+	{
+		/* Chuwi Hi8 (CWI509) */
+		.matches = {
+			DMI_MATCH(DMI_BOARD_VENDOR, "Hampoo"),
+			DMI_MATCH(DMI_BOARD_NAME, "BYT-PA03C"),
+			DMI_MATCH(DMI_SYS_VENDOR, "ilife"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "S806"),
+		},
+		.driver_data = (void *)&chuwi_hi8_info,
+	}, {
+		/* Xiaomi Mi Pad 2 */
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Xiaomi Inc"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "Mipad2"),
+		},
+		.driver_data = (void *)&xiaomi_mipad2_info,
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(dmi, x86_android_tablet_ids);
+
+static int i2c_client_count;
+static struct i2c_client **i2c_clients;
+
+static __init int x86_instantiate_i2c_client(const struct x86_dev_info *dev_info,
+					     int idx)
+{
+	const struct x86_i2c_client_info *client_info = &dev_info->i2c_client_info[idx];
+	struct i2c_board_info board_info = client_info->board_info;
+	struct i2c_adapter *adap;
+	acpi_handle handle;
+	acpi_status status;
+
+	board_info.irq = x86_acpi_irq_helper_get(&client_info->irq_data);
+	if (board_info.irq < 0)
+		return board_info.irq;
+
+	status = acpi_get_handle(NULL, client_info->adapter_path, &handle);
+	if (ACPI_FAILURE(status)) {
+		pr_err("Error could not get %s handle\n", client_info->adapter_path);
+		return -ENODEV;
+	}
+
+	adap = i2c_acpi_find_adapter_by_handle(handle);
+	if (!adap) {
+		pr_err("error could not get %s adapter\n", client_info->adapter_path);
+		return -ENODEV;
+	}
+
+	i2c_clients[idx] = i2c_new_client_device(adap, &board_info);
+	put_device(&adap->dev);
+	if (IS_ERR(i2c_clients[idx]))
+		return dev_err_probe(&adap->dev, PTR_ERR(i2c_clients[idx]),
+				      "creating I2C-client %d\n", idx);
+
+	return 0;
+}
+
+static void x86_android_tablet_cleanup(void)
+{
+	int i;
+
+	for (i = 0; i < i2c_client_count; i++)
+		i2c_unregister_device(i2c_clients[i]);
+
+	kfree(i2c_clients);
+}
+
+static __init int x86_android_tablet_init(void)
+{
+	const struct x86_dev_info *dev_info;
+	const struct dmi_system_id *id;
+	int i, ret = 0;
+
+	id = dmi_first_match(x86_android_tablet_ids);
+	if (!id)
+		return -ENODEV;
+
+	dev_info = id->driver_data;
+
+	i2c_client_count = dev_info->i2c_client_count;
+
+	i2c_clients = kcalloc(i2c_client_count, sizeof(*i2c_clients), GFP_KERNEL);
+	if (!i2c_clients)
+		return -ENOMEM;
+
+	for (i = 0; i < dev_info->i2c_client_count; i++) {
+		ret = x86_instantiate_i2c_client(dev_info, i);
+		if (ret < 0) {
+			x86_android_tablet_cleanup();
+			break;
+		}
+	}
+
+	return ret;
+}
+
+module_init(x86_android_tablet_init);
+module_exit(x86_android_tablet_cleanup);
+
+MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com");
+MODULE_DESCRIPTION("X86 Android tablets DSDT fixups driver");
+MODULE_LICENSE("GPL");