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Subject[PATCH v2] platform/x86: Add driver for Apple gmux device
Date
Apple laptops with hybrid graphics have a device named gmux that
controls the muxing of the LVDS panel between the GPUs as well as screen
brightness. This driver adds support for the gmux device. Only backlight
control is supported initially.

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
---
This contains some minor updates to the previous submission. Changes in
v2:

- Removed unused max_brightness field from struct apple_gmux_data
- Removed unused gmux_write32() function
- Mask off unused bits when reading brightness
- Use gmux_get_brightness() when initializing backlight device
brightness field
- Fix some bad grammar in one of the comments.

drivers/platform/x86/Kconfig | 10 ++
drivers/platform/x86/Makefile | 1 +
drivers/platform/x86/apple-gmux.c | 228 +++++++++++++++++++++++++++++++++++++
3 files changed, 239 insertions(+), 0 deletions(-)
create mode 100644 drivers/platform/x86/apple-gmux.c
diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index f995e6e..a2a9ede 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -779,4 +779,14 @@ config SAMSUNG_Q10
This driver provides support for backlight control on Samsung Q10
and related laptops, including Dell Latitude X200.

+config APPLE_GMUX
+ tristate "Apple Gmux Driver"
+ depends on PNP
+ select BACKLIGHT_CLASS_DEVICE
+ ---help---
+ This driver provides support for the gmux device found on many
+ Apple laptops, which controls the display mux for the hybrid
+ graphics as well as the backlight. Currently only backlight
+ control is supported by the driver.
+
endif # X86_PLATFORM_DEVICES
diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
index 293a320..a49c891 100644
--- a/drivers/platform/x86/Makefile
+++ b/drivers/platform/x86/Makefile
@@ -45,3 +45,4 @@ obj-$(CONFIG_MXM_WMI) += mxm-wmi.o
obj-$(CONFIG_INTEL_MID_POWER_BUTTON) += intel_mid_powerbtn.o
obj-$(CONFIG_INTEL_OAKTRAIL) += intel_oaktrail.o
obj-$(CONFIG_SAMSUNG_Q10) += samsung-q10.o
+obj-$(CONFIG_APPLE_GMUX) += apple-gmux.o
diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c
new file mode 100644
index 0000000..efc1fa9
--- /dev/null
+++ b/drivers/platform/x86/apple-gmux.c
@@ -0,0 +1,228 @@
+/*
+ * Gmux driver for Apple laptops
+ *
+ * Copyright (C) Canonical Ltd. <seth.forshee@canonical.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.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/backlight.h>
+#include <linux/acpi.h>
+#include <linux/pnp.h>
+
+struct apple_gmux_data {
+ unsigned long iostart;
+ unsigned long iolen;
+
+ struct backlight_device *bdev;
+};
+
+/*
+ * gmux port offsets. Many of these are not yet used, but may be in the
+ * future, and it's useful to have them documented here anyhow.
+ */
+#define GMUX_PORT_VERSION_MAJOR 0x04
+#define GMUX_PORT_VERSION_MINOR 0x05
+#define GMUX_PORT_VERSION_RELEASE 0x06
+#define GMUX_PORT_SWITCH_DISPLAY 0x10
+#define GMUX_PORT_SWITCH_GET_DISPLAY 0x11
+#define GMUX_PORT_INTERRUPT_ENABLE 0x14
+#define GMUX_PORT_INTERRUPT_STATUS 0x16
+#define GMUX_PORT_SWITCH_DDC 0x28
+#define GMUX_PORT_SWITCH_EXTERNAL 0x40
+#define GMUX_PORT_SWITCH_GET_EXTERNAL 0x41
+#define GMUX_PORT_DISCRETE_POWER 0x50
+#define GMUX_PORT_MAX_BRIGHTNESS 0x70
+#define GMUX_PORT_BRIGHTNESS 0x74
+
+#define GMUX_MIN_IO_LEN (GMUX_PORT_BRIGHTNESS + 4)
+
+#define GMUX_INTERRUPT_ENABLE 0xff
+#define GMUX_INTERRUPT_DISABLE 0x00
+
+#define GMUX_INTERRUPT_STATUS_ACTIVE 0
+#define GMUX_INTERRUPT_STATUS_DISPLAY (1 << 0)
+#define GMUX_INTERRUPT_STATUS_POWER (1 << 2)
+#define GMUX_INTERRUPT_STATUS_HOTPLUG (1 << 3)
+
+#define GMUX_BRIGHTNESS_MASK 0x00ffffff
+#define GMUX_MAX_BRIGHTNESS GMUX_BRIGHTNESS_MASK
+
+static inline u8 gmux_read8(struct apple_gmux_data *gmux_data, int port)
+{
+ return inb(gmux_data->iostart + port);
+}
+
+static inline void gmux_write8(struct apple_gmux_data *gmux_data, int port,
+ u8 val)
+{
+ outb(val, gmux_data->iostart + port);
+}
+
+static inline u32 gmux_read32(struct apple_gmux_data *gmux_data, int port)
+{
+ return inl(gmux_data->iostart + port);
+}
+
+static int gmux_get_brightness(struct backlight_device *bd)
+{
+ struct apple_gmux_data *gmux_data = bl_get_data(bd);
+ return gmux_read32(gmux_data, GMUX_PORT_BRIGHTNESS) &
+ GMUX_BRIGHTNESS_MASK;
+}
+
+static int gmux_update_status(struct backlight_device *bd)
+{
+ struct apple_gmux_data *gmux_data = bl_get_data(bd);
+ u32 brightness = bd->props.brightness;
+
+ /*
+ * Older gmux versions require writing out lower bytes first then
+ * setting the upper byte to 0 to flush the values. Newer versions
+ * accept a single u32 write, but the old method also works, so we
+ * just use the old method for all gmux versions.
+ */
+ gmux_write8(gmux_data, GMUX_PORT_BRIGHTNESS, brightness);
+ gmux_write8(gmux_data, GMUX_PORT_BRIGHTNESS + 1, brightness >> 8);
+ gmux_write8(gmux_data, GMUX_PORT_BRIGHTNESS + 2, brightness >> 16);
+ gmux_write8(gmux_data, GMUX_PORT_BRIGHTNESS + 3, 0);
+
+ return 0;
+}
+
+static const struct backlight_ops gmux_bl_ops = {
+ .get_brightness = gmux_get_brightness,
+ .update_status = gmux_update_status,
+};
+
+static int __devinit gmux_probe(struct pnp_dev *pnp,
+ const struct pnp_device_id *id)
+{
+ struct apple_gmux_data *gmux_data;
+ struct resource *res;
+ struct backlight_properties props;
+ struct backlight_device *bdev;
+ u8 ver_major, ver_minor, ver_release;
+ int ret = -ENXIO;
+
+ gmux_data = kzalloc(sizeof(*gmux_data), GFP_KERNEL);
+ if (!gmux_data)
+ return -ENOMEM;
+ pnp_set_drvdata(pnp, gmux_data);
+
+ res = pnp_get_resource(pnp, IORESOURCE_IO, 0);
+ if (!res) {
+ pr_err("Failed to find gmux I/O resource\n");
+ goto err_free;
+ }
+
+ gmux_data->iostart = res->start;
+ gmux_data->iolen = res->end - res->start;
+
+ if (gmux_data->iolen < GMUX_MIN_IO_LEN) {
+ pr_err("gmux I/O region too small (%lu < %u)\n",
+ gmux_data->iolen, GMUX_MIN_IO_LEN);
+ goto err_free;
+ }
+
+ if (!request_region(gmux_data->iostart, gmux_data->iolen,
+ "Apple gmux")) {
+ pr_err("gmux I/O already in use\n");
+ goto err_free;
+ }
+
+ /*
+ * On some machines the gmux is in ACPI even thought the machine
+ * doesn't really have a gmux. Check for invalid version information
+ * to detect this.
+ */
+ ver_major = gmux_read8(gmux_data, GMUX_PORT_VERSION_MAJOR);
+ ver_minor = gmux_read8(gmux_data, GMUX_PORT_VERSION_MINOR);
+ ver_release = gmux_read8(gmux_data, GMUX_PORT_VERSION_RELEASE);
+ if (ver_major == 0xff && ver_minor == 0xff && ver_release == 0xff) {
+ pr_info("gmux device not present\n");
+ ret = -ENODEV;
+ goto err_release;
+ }
+
+ pr_info("Found gmux version %d.%d.%d\n", ver_major, ver_minor,
+ ver_release);
+
+ memset(&props, 0, sizeof(props));
+ props.type = BACKLIGHT_PLATFORM;
+ props.max_brightness = gmux_read32(gmux_data, GMUX_PORT_MAX_BRIGHTNESS);
+
+ /*
+ * Currently it's assumed that the maximum brightness is less than
+ * 2^24 for compatibility with old gmux versions. Cap the max
+ * brightness at this value, but print a warning if the hardware
+ * reports something higher so that it can be fixed.
+ */
+ if (WARN_ON(props.max_brightness > GMUX_MAX_BRIGHTNESS))
+ props.max_brightness = GMUX_MAX_BRIGHTNESS;
+
+ bdev = backlight_device_register("gmux_backlight", &pnp->dev,
+ gmux_data, &gmux_bl_ops, &props);
+ if (IS_ERR(bdev)) {
+ ret = PTR_ERR(bdev);
+ goto err_release;
+ }
+
+ gmux_data->bdev = bdev;
+ bdev->props.brightness = gmux_get_brightness(bdev);
+ backlight_update_status(bdev);
+
+ return 0;
+
+err_release:
+ release_region(gmux_data->iostart, gmux_data->iolen);
+err_free:
+ kfree(gmux_data);
+ return ret;
+}
+
+static void __devexit gmux_remove(struct pnp_dev *pnp)
+{
+ struct apple_gmux_data *gmux_data = pnp_get_drvdata(pnp);
+
+ backlight_device_unregister(gmux_data->bdev);
+ release_region(gmux_data->iostart, gmux_data->iolen);
+ kfree(gmux_data);
+}
+
+static const struct pnp_device_id gmux_device_ids[] = {
+ {"APP000B", 0},
+ {"", 0}
+};
+
+static struct pnp_driver gmux_pnp_driver = {
+ .name = "apple-gmux",
+ .probe = gmux_probe,
+ .remove = __devexit_p(gmux_remove),
+ .id_table = gmux_device_ids,
+};
+
+static int __init apple_gmux_init(void)
+{
+ return pnp_register_driver(&gmux_pnp_driver);
+}
+
+static void __exit apple_gmux_exit(void)
+{
+ pnp_unregister_driver(&gmux_pnp_driver);
+}
+
+module_init(apple_gmux_init);
+module_exit(apple_gmux_exit);
+
+MODULE_AUTHOR("Seth Forshee <seth.forshee@canonical.com>");
+MODULE_DESCRIPTION("Apple Gmux Driver");
+MODULE_LICENSE("GPL");
+MODULE_DEVICE_TABLE(pnp, gmux_device_ids);
--
1.7.9


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