[PATCH v3 0/2] Add driver for Apple gmux device

[PATCH v3 0/2] Add driver for Apple gmux device

[Seth Forshee]

Apple laptops with hybrid graphics have a device named gmux that is used
for switching between GPUs and backlight control. On many models this is
the only reliable method for controlling the backlight.

This series adds initial support for the gmux device, along with
anciallary support for disabling apple_bl when the gmux device is
detected. Initially only backlight control is supported.

Changes since v2:

 - Add prerequisite patch for apple_bl to support disabling this
   backlight when a gmux backlight device is present.

 - Unregister acpi_video when a gmux backlight device is present.

Thanks,
Seth


Seth Forshee (2):
  apple_bl: Add register/unregister functions
  platform/x86: Add driver for Apple gmux device

 drivers/platform/x86/Kconfig       |   11 ++
 drivers/platform/x86/Makefile      |    1 +
 drivers/platform/x86/apple-gmux.c  |  242 ++++++++++++++++++++++++++++++++++++
 drivers/video/backlight/apple_bl.c |   23 +++-
 include/linux/apple_bl.h           |   11 ++
 5 files changed, 286 insertions(+), 2 deletions(-)
 create mode 100644 drivers/platform/x86/apple-gmux.c
 create mode 100644 include/linux/apple_bl.h

[PATCH v3 1/2] apple_bl: Add register/unregister functions

[Seth Forshee]

Add functions to allow other modules to enable or disable apple_bl. This
will be used by the gmux driver to disable apple_bl when the gmux is
present, as it is a better and more reliable option for brightness
control.

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
---
 drivers/video/backlight/apple_bl.c |   23 +++++++++++++++++++++--
 include/linux/apple_bl.h           |   11 +++++++++++
 2 files changed, 32 insertions(+), 2 deletions(-)
 create mode 100644 include/linux/apple_bl.h

diff --git a/drivers/video/backlight/apple_bl.c b/drivers/video/backlight/apple_bl.c
index be98d15..87332ce 100644
--- a/drivers/video/backlight/apple_bl.c
+++ b/drivers/video/backlight/apple_bl.c
@@ -24,6 +24,7 @@
 #include <linux/io.h>
 #include <linux/pci.h>
 #include <linux/acpi.h>
+#include <linux/atomic.h>
 
 static struct backlight_device *apple_backlight_device;
 
@@ -221,14 +222,32 @@ static struct acpi_driver apple_bl_driver = {
 	},
 };
 
+atomic_t apple_bl_register_count = ATOMIC_INIT(0);
+
+int apple_bl_register(void)
+{
+	if (atomic_xchg(&apple_bl_register_count, 1) == 0)
+		return acpi_bus_register_driver(&apple_bl_driver);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(apple_bl_register);
+
+void apple_bl_unregister(void)
+{
+	if (atomic_xchg(&apple_bl_register_count, 0) == 1)
+		acpi_bus_unregister_driver(&apple_bl_driver);
+}
+EXPORT_SYMBOL_GPL(apple_bl_unregister);
+
 static int __init apple_bl_init(void)
 {
-	return acpi_bus_register_driver(&apple_bl_driver);
+	return apple_bl_register();
 }
 
 static void __exit apple_bl_exit(void)
 {
-	acpi_bus_unregister_driver(&apple_bl_driver);
+	apple_bl_unregister();
 }
 
 module_init(apple_bl_init);
diff --git a/include/linux/apple_bl.h b/include/linux/apple_bl.h
new file mode 100644
index 0000000..5c86ae5
--- /dev/null
+++ b/include/linux/apple_bl.h
@@ -0,0 +1,11 @@
+/*
+ * apple_bl exported symbols
+ */
+
+#ifndef _LINUX_APPLE_BL_H
+#define _LINUX_APPLE_BL_H
+
+extern int apple_bl_register(void);
+extern void apple_bl_unregister(void);
+
+#endif
-- 
1.7.9.1

[PATCH v3 2/2] platform/x86: Add driver for Apple gmux device

[Seth Forshee]

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>
---
 drivers/platform/x86/Kconfig      |   11 ++
 drivers/platform/x86/Makefile     |    1 +
 drivers/platform/x86/apple-gmux.c |  242 +++++++++++++++++++++++++++++++++++++
 3 files changed, 254 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..cbc7a77 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -779,4 +779,15 @@ 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
+	select BACKLIGHT_APPLE
+	---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..c81e31f
--- /dev/null
+++ b/drivers/platform/x86/apple-gmux.c
@@ -0,0 +1,242 @@
+/*
+ *  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>
+#include <linux/apple_bl.h>
+#include <acpi/video.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);
+
+	/*
+	 * The backlight situation on Macs is complicated. If the gmux is
+	 * present it's the best choice, because it always works for
+	 * backlight control and supports more levels than other options.
+	 * Disable the other backlight choices.
+	 */
+	acpi_video_unregister();
+	apple_bl_unregister();
+
+	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);
+
+	acpi_video_register();
+	apple_bl_register();
+}
+
+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);
-- 
1.7.9.1

Re: [PATCH v3 1/2] apple_bl: Add register/unregister functions

[Seth Forshee]

On Thu, Mar 15, 2012 at 04:32:07PM -0500, Seth Forshee wrote:
> +atomic_t apple_bl_register_count = ATOMIC_INIT(0);

Noticed that I forgot to make this static. I had also intended to rename
it; it was originally a reference count but I decided that didn't make
sense. I'll wait to see if there are any other comments. If this
otherwise looks okay I'll send an update for this patch.

Seth

Re: [PATCH v3 1/2] apple_bl: Add register/unregister functions

[Matthew Garrett]

On Thu, Mar 15, 2012 at 04:32:07PM -0500, Seth Forshee wrote:

> +extern int apple_bl_register(void);
> +extern void apple_bl_unregister(void);
> +
> +#endif

Ideally you'd provide stub functions here so gmux can be built even if 
apple_bl isn't.

-- 
Matthew Garrett | mjg59@srcf.ucam.org

Re: [PATCH v3 2/2] platform/x86: Add driver for Apple gmux device

[Matthew Garrett]

On Thu, Mar 15, 2012 at 04:32:08PM -0500, Seth Forshee wrote:

> +	select BACKLIGHT_APPLE

If you add the aforementioned stubs then you can drop this. Otherwise, 
looks good.

-- 
Matthew Garrett | mjg59@srcf.ucam.org