[PATCH] apple-gmux: Add support for message box interface (as found in MBP10,1/Retina MacBook Pro)

[PATCH] apple-gmux: Add support for message box interface (as found in MBP10,1/Retina MacBook Pro)

[Bernhard Froemel]

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-----BEGIN PGP SIGNED MESSAGE-----
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Dear all,

Apple changed the interface to the gmux device in recent models (at
least MBP 10,1).
This patch [1] (also attached) against 3.6-rc1 adds support for the
changed interface.
Previously the interface to gmux registers was memory mapped, now there
is a message box
interface (address, status, data I/O ports). The gmux register layout
itself seems to be unchanged.
I chose rather safe delays (1 ms) for access relaxation -- without any
relaxation the
communication is unreliable for me.
If someone with an older MBP could test whether the interface detection
(DPM/classic) works it
would be great. I used a similar detection routine Apple is using in
their driver.


I see that there is a lot going on concerning and related to the
apple-gmux currently:
https://lkml.org/lkml/2012/7/9/715
https://lkml.org/lkml/2012/8/3/300

I could apply all those patches successfully and run a halfway decent
setup with working
X, virtual consoles, backlight control, suspend/resume and even with
(limited) GPU switching
during runtime:
http://ubuntuforums.org/showpost.php?p=12167124&postcount=89

Cheers,
 Bernhard

[1] http://luna.vmars.tuwien.ac.at/~froemel/rmbp/patch-apple-gmux.txt
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[-- Attachment #2: patch-apple-gmux.txt --]
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Signed-off-by: Bernhard Froemel <froemel@vmars.tuwien.ac.at>

--- a/drivers/platform/x86/apple-gmux.c	2012-08-03 02:38:10.000000000 +0300
+++ b/drivers/platform/x86/apple-gmux.c	2012-08-13 12:04:25.366408899 +0300
@@ -2,6 +2,7 @@
  *  Gmux driver for Apple laptops
  *
  *  Copyright (C) Canonical Ltd. <seth.forshee@canonical.com>
+ *  Copyright (C) 2012 Bernhard Froemel <froemel@vmars.tuwien.ac.at>
  *
  *  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
@@ -18,12 +19,15 @@
 #include <linux/pnp.h>
 #include <linux/apple_bl.h>
 #include <linux/slab.h>
+#include <linux/delay.h>
 #include <acpi/video.h>
 #include <asm/io.h>
 
 struct apple_gmux_data {
 	unsigned long iostart;
 	unsigned long iolen;
+	int is_dpm;
+	struct semaphore dpm_lock;
 
 	struct backlight_device *bdev;
 };
@@ -45,6 +49,22 @@
 #define GMUX_PORT_DISCRETE_POWER	0x50
 #define GMUX_PORT_MAX_BRIGHTNESS	0x70
 #define GMUX_PORT_BRIGHTNESS		0x74
+#define GMUX_PORT_DPM_CHK		0x00
+#define GMUX_PORT_DPM_REG1		0xcc
+#define GMUX_PORT_DPM_REG2		0xcd
+
+#define DPM_REG1			0xaa
+#define DPM_REG2			0x55
+
+#define GMUX_PORT_DPM_RADDR		0xd0
+#define GMUX_PORT_DPM_WADDRSTAT		0xd4
+#define GMUX_PORT_DPM_DAT0		0xc2
+#define GMUX_PORT_DPM_DAT1		0xc3
+#define GMUX_PORT_DPM_DAT2		0xc4
+#define GMUX_PORT_DPM_DAT3		0xc5
+
+#define GMUX_DPM_CMD_TO			20
+#define GMUX_DPM_CMD_DLY		1 /* in ms */
 
 #define GMUX_MIN_IO_LEN			(GMUX_PORT_BRIGHTNESS + 4)
 
@@ -59,27 +79,151 @@
 #define GMUX_BRIGHTNESS_MASK		0x00ffffff
 #define GMUX_MAX_BRIGHTNESS		GMUX_BRIGHTNESS_MASK
 
+static inline int gmux_dpm_read(struct apple_gmux_data *gmux_data, u8 reg,
+	u8 size, u32 *ret);
+static inline int gmux_dpm_write(struct apple_gmux_data *gmux_data, u8 reg,
+	u8 size, u32 val);
+
 static inline u8 gmux_read8(struct apple_gmux_data *gmux_data, int port)
 {
+	if (gmux_data->is_dpm) {
+		u32 ret;
+		gmux_dpm_read(gmux_data, port, 1, &ret);
+		return ret;
+	}
 	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);
+	if (gmux_data->is_dpm)
+		gmux_dpm_write(gmux_data, port, 1, val);
+	else
+		outb(val, gmux_data->iostart + port);
 }
 
 static inline u32 gmux_read32(struct apple_gmux_data *gmux_data, int port)
 {
+	if (gmux_data->is_dpm) {
+		u32 ret;
+		gmux_dpm_read(gmux_data, port, 4, &ret);
+		return ret;
+	}
 	return inl(gmux_data->iostart + port);
 }
 
+
+static inline u8 gmux_dpm_cmd_rdy(void)
+{
+	u8 status = inb(GMUX_PORT_DPM_WADDRSTAT);
+	u8 to = GMUX_DPM_CMD_TO;
+	while (status == 0 && to) {
+		inb(GMUX_PORT_DPM_RADDR);
+		msleep(GMUX_DPM_CMD_DLY);
+		status = inb(GMUX_PORT_DPM_WADDRSTAT);
+		to--;
+		msleep(GMUX_DPM_CMD_DLY);
+	}
+	return to != 0;
+}
+
+static inline u8 gmux_dpm_cmd_done(void)
+{
+	uint8_t status = 0;
+	uint8_t to = GMUX_DPM_CMD_TO;
+	do {
+		status = inb(GMUX_PORT_DPM_WADDRSTAT);
+		to--;
+		msleep(GMUX_DPM_CMD_DLY);
+	} while (status == 0 && to);
+	if (status == 0)
+		inb(GMUX_PORT_DPM_RADDR);
+	return to != 0;
+}
+
+
+static inline int gmux_dpm_read(struct apple_gmux_data *gmux_data, u8 reg,
+	u8 size, u32 *ret)
+{
+	*ret = 0x0;
+
+	if (down_interruptible(&gmux_data->dpm_lock))
+		return 0;
+
+	if (!gmux_dpm_cmd_rdy()) {
+		pr_err("gmux_dpm_cmd_rdy failed.");
+		goto gmux_dpm_read_failed;
+	}
+	outb(reg, gmux_data->iostart + GMUX_PORT_DPM_RADDR);
+	if (!gmux_dpm_cmd_done()) {
+		pr_err("gmux_dpm_cmd_done failed.");
+		goto gmux_dpm_read_failed;
+	}
+	if (size == 1) {
+		*ret = inb(gmux_data->iostart + GMUX_PORT_DPM_DAT0);
+	} else if (size == 2) {
+		*ret = inb(gmux_data->iostart + GMUX_PORT_DPM_DAT1) << 8;
+		*ret |= inb(gmux_data->iostart + GMUX_PORT_DPM_DAT0);
+	} else if (size == 4) {
+		*ret = inb(gmux_data->iostart + GMUX_PORT_DPM_DAT3) << 24;
+		*ret |= inb(gmux_data->iostart + GMUX_PORT_DPM_DAT2) << 16;
+		*ret |= inb(gmux_data->iostart + GMUX_PORT_DPM_DAT1) << 8;
+		*ret |= inb(gmux_data->iostart + GMUX_PORT_DPM_DAT0);
+	} else
+		goto gmux_dpm_read_failed;
+
+	up(&gmux_data->dpm_lock);
+	return 1;
+
+gmux_dpm_read_failed:
+	up(&gmux_data->dpm_lock);
+	return 0;
+}
+
+static inline int gmux_dpm_write(struct apple_gmux_data *gmux_data, u8 reg,
+	u8 size, u32 val)
+{
+	if (down_interruptible(&gmux_data->dpm_lock))
+		return 0;
+
+	if (size == 1) {
+		outb(val, gmux_data->iostart + GMUX_PORT_DPM_DAT0);
+	} else if (size == 2) {
+		outb(val>>8, gmux_data->iostart + GMUX_PORT_DPM_DAT1);
+		outb(val, gmux_data->iostart + GMUX_PORT_DPM_DAT0);
+	} else if (size == 4) {
+		outb(val>>24, gmux_data->iostart + GMUX_PORT_DPM_DAT3);
+		outb(val>>16, gmux_data->iostart + GMUX_PORT_DPM_DAT2);
+		outb(val>>8, gmux_data->iostart + GMUX_PORT_DPM_DAT1);
+		outb(val, gmux_data->iostart + GMUX_PORT_DPM_DAT0);
+	} else
+		goto gmux_dpm_write_failed;
+
+	if (!gmux_dpm_cmd_rdy()) {
+		pr_err("gmux_dpm_cmd_rdy failed.");
+		goto gmux_dpm_write_failed;
+
+	}
+	outb(reg, gmux_data->iostart + GMUX_PORT_DPM_WADDRSTAT);
+	if (!gmux_dpm_cmd_done()) {
+		pr_err("gmux_dpm_cmd_done failed.");
+		goto gmux_dpm_write_failed;
+	}
+
+	up(&gmux_data->dpm_lock);
+	return 1;
+
+gmux_dpm_write_failed:
+	up(&gmux_data->dpm_lock);
+	return 0;
+}
+
 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;
+		GMUX_BRIGHTNESS_MASK;
 }
 
 static int gmux_update_status(struct backlight_device *bd)
@@ -90,16 +234,23 @@
 	if (bd->props.state & BL_CORE_SUSPENDED)
 		return 0;
 
-	/*
-	 * 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);
+	if (gmux_data->is_dpm) {
+		gmux_dpm_write(gmux_data, GMUX_PORT_BRIGHTNESS, 4, brightness);
+	} else {
+		/*
+		 * 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
+		 * classic 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;
 }
@@ -117,12 +268,14 @@
 	struct resource *res;
 	struct backlight_properties props;
 	struct backlight_device *bdev;
-	u8 ver_major, ver_minor, ver_release;
+	u8 ver_major, ver_minor, ver_release, dpm_chk;
 	int ret = -ENXIO;
 
 	gmux_data = kzalloc(sizeof(*gmux_data), GFP_KERNEL);
 	if (!gmux_data)
 		return -ENOMEM;
+	gmux_data->is_dpm = 0;
+	sema_init(&gmux_data->dpm_lock, 1);
 	pnp_set_drvdata(pnp, gmux_data);
 
 	res = pnp_get_resource(pnp, IORESOURCE_IO, 0);
@@ -146,22 +299,51 @@
 		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.
-	 */
+	dpm_chk = gmux_read8(gmux_data, GMUX_PORT_DPM_CHK);
 	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;
+	if (dpm_chk != ver_major) {
+		/*
+		 * 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_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_err("gmux device seems to be not present\n");
+			ret = -ENODEV;
+			goto err_release;
+		}
+		gmux_data->is_dpm = 0;
+	} else { /* possibly a dp micro variant, found in MBP 10,1 */
+		/* check presence */
+		gmux_write8(gmux_data, GMUX_PORT_DPM_REG1, DPM_REG1);
+		gmux_write8(gmux_data, GMUX_PORT_DPM_REG2, DPM_REG2);
+		if (gmux_read8(gmux_data, GMUX_PORT_DPM_REG1) == DPM_REG1 &&
+			gmux_read8(gmux_data,
+				GMUX_PORT_DPM_REG2) == DPM_REG2) {
+			u32 version = 0;
+			gmux_data->is_dpm = 1;
+
+			if (!gmux_dpm_read(gmux_data,
+				GMUX_PORT_VERSION_MAJOR, 4, &version)) {
+				pr_err("could not obtain version information from gmux. Bailing out.\n");
+				ret = -ENODEV;
+				goto err_release;
+			}
+			ver_major = (version >> 24) & 0xff;
+			ver_minor = (version >> 16) & 0xff;
+			ver_release = (version >> 8) & 0xff;
+		} else {
+			pr_err("gmux device seems to be not present\n");
+			ret = -ENODEV;
+			goto err_release;
+		}
 	}
 
-	pr_info("Found gmux version %d.%d.%d\n", ver_major, ver_minor,
-		ver_release);
+	pr_info("Found gmux version %d.%d.%d [%s]\n", ver_major, ver_minor,
+		ver_release, (gmux_data->is_dpm ? "dpm" : "classic"));
 
 	memset(&props, 0, sizeof(props));
 	props.type = BACKLIGHT_PLATFORM;

[-- Attachment #3: patch-apple-gmux.txt.sig --]
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Re: [PATCH] apple-gmux: Add support for message box interface (as found in MBP10,1/Retina MacBook Pro)

[Seth Forshee]

On Mon, Aug 13, 2012 at 11:42:49AM +0200, Bernhard Froemel wrote:
> 
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Dear all,
> 
> Apple changed the interface to the gmux device in recent models (at
> least MBP 10,1).
> This patch [1] (also attached) against 3.6-rc1 adds support for the
> changed interface.
> Previously the interface to gmux registers was memory mapped, now there
> is a message box
> interface (address, status, data I/O ports). The gmux register layout
> itself seems to be unchanged.
> I chose rather safe delays (1 ms) for access relaxation -- without any
> relaxation the
> communication is unreliable for me.
> If someone with an older MBP could test whether the interface detection
> (DPM/classic) works it
> would be great. I used a similar detection routine Apple is using in
> their driver.

Matthew also made some progress with this last week, at least enough to
get the backlight working. From what I remember of looking at his
changes these look fairly similar, but I think his implementation looked
cleaner and possibly more complete.

> I see that there is a lot going on concerning and related to the
> apple-gmux currently:
> https://lkml.org/lkml/2012/7/9/715
> https://lkml.org/lkml/2012/8/3/300

I'm slowly making progress on the graphics switching stuff. I've got
patches for vga_switcheroo and apple-gmux that make the muxing itself
work fine, the problems now all revolve around making the graphics
drivers deal with difficult behavior from Apple machines.

Thanks,
Seth

Re: [PATCH] apple-gmux: Add support for message box interface (as found in MBP10,1/Retina MacBook Pro)

[Bernhard Froemel]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 08/13/2012 07:09 PM, Seth Forshee wrote:
> Matthew also made some progress with this last week, at least
> enough to get the backlight working. From what I remember of
> looking at his changes these look fairly similar, but I think his
> implementation looked cleaner and possibly more complete.
Aw.. pity; then I wasted ~8h :/ .. but I had fun anyway.  Is there
another (patch) thread where this is already discussed?

>> I see that there is a lot going on concerning and related to the 
>> apple-gmux currently: https://lkml.org/lkml/2012/7/9/715 
>> https://lkml.org/lkml/2012/8/3/300
> 
> I'm slowly making progress on the graphics switching stuff. I've
> got patches for vga_switcheroo and apple-gmux that make the muxing
> itself work fine, the problems now all revolve around making the
> graphics drivers deal with difficult behavior from Apple machines.
Looking forward to it, although the essential stuff (for Intel GPU
operation only) already works well for me.
In case you need something tested you can always CC me!

Bernhard
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Re: [PATCH] apple-gmux: Add support for message box interface (as found in MBP10,1/Retina MacBook Pro)

[Greg KH]

On Mon, Aug 13, 2012 at 08:01:33PM +0200, Bernhard Froemel wrote:
> On 08/13/2012 07:09 PM, Seth Forshee wrote:
> > Matthew also made some progress with this last week, at least
> > enough to get the backlight working. From what I remember of
> > looking at his changes these look fairly similar, but I think his
> > implementation looked cleaner and possibly more complete.
> Aw.. pity; then I wasted ~8h :/ .. but I had fun anyway.  Is there
> another (patch) thread where this is already discussed?
> 
> >> I see that there is a lot going on concerning and related to the 
> >> apple-gmux currently: https://lkml.org/lkml/2012/7/9/715 
> >> https://lkml.org/lkml/2012/8/3/300
> > 
> > I'm slowly making progress on the graphics switching stuff. I've
> > got patches for vga_switcheroo and apple-gmux that make the muxing
> > itself work fine, the problems now all revolve around making the
> > graphics drivers deal with difficult behavior from Apple machines.
> Looking forward to it, although the essential stuff (for Intel GPU
> operation only) already works well for me.
> In case you need something tested you can always CC me!

So with this patch you don't have to boot to os-x to change the graphics
card and it works properly?

thanks,

greg k-h

Re: [PATCH] apple-gmux: Add support for message box interface (as found in MBP10,1/Retina MacBook Pro)

[Seth Forshee]

On Mon, Aug 13, 2012 at 08:01:33PM +0200, Bernhard Froemel wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> On 08/13/2012 07:09 PM, Seth Forshee wrote:
> > Matthew also made some progress with this last week, at least
> > enough to get the backlight working. From what I remember of
> > looking at his changes these look fairly similar, but I think his
> > implementation looked cleaner and possibly more complete.
> Aw.. pity; then I wasted ~8h :/ .. but I had fun anyway.  Is there
> another (patch) thread where this is already discussed?

It was discussed briefly on irc.

http://irclogs.ubuntu.com/2012/08/09/%23ubuntu-kernel.txt

Re: [PATCH] apple-gmux: Add support for message box interface (as found in MBP10,1/Retina MacBook Pro)

[Seth Forshee]

On Mon, Aug 13, 2012 at 11:13:44AM -0700, Greg KH wrote:
> On Mon, Aug 13, 2012 at 08:01:33PM +0200, Bernhard Froemel wrote:
> > On 08/13/2012 07:09 PM, Seth Forshee wrote:
> > > Matthew also made some progress with this last week, at least
> > > enough to get the backlight working. From what I remember of
> > > looking at his changes these look fairly similar, but I think his
> > > implementation looked cleaner and possibly more complete.
> > Aw.. pity; then I wasted ~8h :/ .. but I had fun anyway.  Is there
> > another (patch) thread where this is already discussed?
> > 
> > >> I see that there is a lot going on concerning and related to the 
> > >> apple-gmux currently: https://lkml.org/lkml/2012/7/9/715 
> > >> https://lkml.org/lkml/2012/8/3/300
> > > 
> > > I'm slowly making progress on the graphics switching stuff. I've
> > > got patches for vga_switcheroo and apple-gmux that make the muxing
> > > itself work fine, the problems now all revolve around making the
> > > graphics drivers deal with difficult behavior from Apple machines.
> > Looking forward to it, although the essential stuff (for Intel GPU
> > operation only) already works well for me.
> > In case you need something tested you can always CC me!
> 
> So with this patch you don't have to boot to os-x to change the graphics
> card and it works properly?

No, this one is only going to get you backlight control. There is a
switching patch ([1], see patch 12), but based on Matthew's comments it
sounds like i915 will need some work before graphics switching will
work.

Seth

[1] http://people.canonical.com/~sforshee/apple-gmux-patches/

Re: [PATCH] apple-gmux: Add support for message box interface (as found in MBP10,1/Retina MacBook Pro)

[Seth Forshee]

On Mon, Aug 13, 2012 at 01:21:16PM -0500, Seth Forshee wrote:
> On Mon, Aug 13, 2012 at 11:13:44AM -0700, Greg KH wrote:
> > On Mon, Aug 13, 2012 at 08:01:33PM +0200, Bernhard Froemel wrote:
> > > On 08/13/2012 07:09 PM, Seth Forshee wrote:
> > > > Matthew also made some progress with this last week, at least
> > > > enough to get the backlight working. From what I remember of
> > > > looking at his changes these look fairly similar, but I think his
> > > > implementation looked cleaner and possibly more complete.
> > > Aw.. pity; then I wasted ~8h :/ .. but I had fun anyway.  Is there
> > > another (patch) thread where this is already discussed?
> > > 
> > > >> I see that there is a lot going on concerning and related to the 
> > > >> apple-gmux currently: https://lkml.org/lkml/2012/7/9/715 
> > > >> https://lkml.org/lkml/2012/8/3/300
> > > > 
> > > > I'm slowly making progress on the graphics switching stuff. I've
> > > > got patches for vga_switcheroo and apple-gmux that make the muxing
> > > > itself work fine, the problems now all revolve around making the
> > > > graphics drivers deal with difficult behavior from Apple machines.
> > > Looking forward to it, although the essential stuff (for Intel GPU
> > > operation only) already works well for me.
> > > In case you need something tested you can always CC me!
> > 
> > So with this patch you don't have to boot to os-x to change the graphics
> > card and it works properly?
> 
> No, this one is only going to get you backlight control. There is a
> switching patch ([1], see patch 12), but based on Matthew's comments it
> sounds like i915 will need some work before graphics switching will
> work.

I should note that this patch alone won't support the gmux on the
retina, it would need to be merged with one of the patches that adds
support for that gmux.

> 
> Seth
> 
> [1] http://people.canonical.com/~sforshee/apple-gmux-patches/

Re: [PATCH] apple-gmux: Add support for message box interface (as found in MBP10,1/Retina MacBook Pro)

[Bernhard Froemel]

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On 08/13/2012 08:21 PM, Seth Forshee wrote:
>> So with this patch you don't have to boot to os-x to change the
>> graphics card and it works properly?
No - although I only need to boot to OSX once and force integrated
GPU. The setting seems to remain persistent across reboots and power
cycles (probably stored somewhere as an EFI variable?).

Anyway, (like Seth and Matthew) I think the problem is i915 and not
the gmux device. It seems to me that if i915 has no output connected
during startup/module initialization it won't find one later on: e.g.
even though gmux is setup correctly I get a black screen and in my X log:
(WW) intel(0): No outputs definitely connected, trying again...


> 
> No, this one is only going to get you backlight control.
Actually, my patch only allows you to talk to the gmux device of
MBP10,1. Only with forcing the integrated GPU in OSX and with:
> [..] switching patch ([1], see patch 12), [..]
the MBP works well with the Intel GPU across reboots and suspends/resumes.
(With 'echo OFF > /sys/kernel/debug/vgaswitcheroo/switch' the discrete
GPU can be turned off and I get an estimate of 7 hours runtime on
lowest brightness settings)

Also in support of that the problem is with i915 is the fact that
actual runtime GPU switching works (2 times) if the MBP is booted with
the Intel GPU. See my post on the Ubuntu forums:
http://ubuntuforums.org/showpost.php?p=12167124&postcount=89

Bernhard

> 
> [1] http://people.canonical.com/~sforshee/apple-gmux-patches/
> 

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Re: [PATCH] apple-gmux: Add support for message box interface (as found in MBP10,1/Retina MacBook Pro)

[Bernhard Froemel]

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On 08/13/2012 08:17 PM, Seth Forshee wrote:
> It was discussed briefly on irc.
> 
> http://irclogs.ubuntu.com/2012/08/09/%23ubuntu-kernel.txt
> 
Yes, it's very similar. Don't want to start any wars here ;) but:
>>> but I think his implementation looked cleaner
I only occasionally write kernel code, but can't there be any
concurrency issues during reads/writes of internal gmux registers (I
used a semaphore to prevent that)? Especially if vga_switcheroo also
taps in?

Aw.. maybe we should wait until Matthew actually posts his patch.
Seems like we invested both some work, pity that I didn't know of it.

Bernhard
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Re: [PATCH] apple-gmux: Add support for message box interface (as found in MBP10,1/Retina MacBook Pro)

[Seth Forshee]

On Mon, Aug 13, 2012 at 08:59:41PM +0200, Bernhard Froemel wrote:
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> 
> On 08/13/2012 08:17 PM, Seth Forshee wrote:
> > It was discussed briefly on irc.
> > 
> > http://irclogs.ubuntu.com/2012/08/09/%23ubuntu-kernel.txt
> > 
> Yes, it's very similar. Don't want to start any wars here ;) but:
> >>> but I think his implementation looked cleaner
> I only occasionally write kernel code, but can't there be any
> concurrency issues during reads/writes of internal gmux registers (I
> used a semaphore to prevent that)? Especially if vga_switcheroo also
> taps in?

There aren't concurrency issues right now since only backlight is
supported, and the backlight class driver serializes callbacks into the
driver with a mutex. But when switcheroo support is added some
concurrency protection is probably necessary. A mutex should be used
rather than a semaphore however.

Seth