[2/3] Split VGA default device handler out of VGA arbiter

Submitted by Daniel Axtens on Aug. 4, 2017, 10:20 a.m.

Details

Message ID 20170804102033.27731-3-dja@axtens.net
State Changes Requested
Headers show

Commit Message

Daniel Axtens Aug. 4, 2017, 10:20 a.m.
A system without PCI legacy resources (e.g. ARM64, powerpc) may
find that no default/boot VGA device has been marked, because the
VGA arbiter checks for legacy resource decoding before marking a
card as default.

Split the small bit of code that does default VGA handling out from
the arbiter. Add a Kconfig option to allow the kernel to be built
with just the default handling, or the arbiter and default handling.
(You can try with the arbiter and no default handling - I can't see
why that wouldn't work but it seems a bit odd to try.)

Add handling for devices that should be marked as default but aren't
handled by the vga arbiter by adding a late initcall and a class
enable hook. If there is no default from vgaarb then the first card
that is enabled, has a driver bound, and can decode memory or I/O
will be marked as default.

Signed-off-by: Daniel Axtens <dja@axtens.net>

---

I haven't tested this particularly deeply just yet as I wanted to
see if anyone had Strong Feelings before I put too much time into
testing. I have verified that it works on ppc with qemu TCG, both
with and without the following patch.

I know this adds another config option and that's a bit sad, but
we can't include it unconditionally as it depends on PCI.
Suggestions welcome.
---
 arch/ia64/pci/fixup.c            |   2 +-
 arch/powerpc/kernel/pci-common.c |   2 +-
 arch/x86/pci/fixup.c             |   2 +-
 arch/x86/video/fbdev.c           |   2 +-
 drivers/gpu/vga/Kconfig          |  12 +++
 drivers/gpu/vga/Makefile         |   1 +
 drivers/gpu/vga/vga_default.c    | 159 +++++++++++++++++++++++++++++++++++++++
 drivers/gpu/vga/vga_switcheroo.c |   2 +-
 drivers/gpu/vga/vgaarb.c         |  41 +---------
 drivers/pci/pci-sysfs.c          |   2 +-
 include/linux/vga_default.h      |  44 +++++++++++
 include/linux/vgaarb.h           |  14 ----
 12 files changed, 225 insertions(+), 58 deletions(-)
 create mode 100644 drivers/gpu/vga/vga_default.c
 create mode 100644 include/linux/vga_default.h

Comments

Lukas Wunner Aug. 5, 2017, 6:57 a.m.
On Fri, Aug 04, 2017 at 08:20:32PM +1000, Daniel Axtens wrote:
> A system without PCI legacy resources (e.g. ARM64, powerpc) may
> find that no default/boot VGA device has been marked, because the
> VGA arbiter checks for legacy resource decoding before marking a
> card as default.

Would it be feasible to just sprinkle some "if (IS_ENABLED(CONFIG_X86))"
over the portions of vgaarb.c that deal with legacy resources?

I'm missing some context as to the negative consequences you're
experiencing on other arches (the cover letter merely refers to
"quirks in ppc and concerns in arm land" and is missing links to
archived versions of v1 and v2), but clearly legacy resources are
x86-specific so any code dealing with them seems superfluous on
other arches and should be marked as such.

Please cc dri-devel when proposing changes to vgaarb.c (see
MAINTAINERS).

Thanks,

Lukas
Daniel Axtens Aug. 6, 2017, 11:49 p.m.
Hi Lukas,

Let me reply "back-to-front":

> Please cc dri-devel when proposing changes to vgaarb.c (see
> MAINTAINERS).

Sorry, will do in future.

> I'm missing some context as to the negative consequences you're
> experiencing on other arches (the cover letter merely refers to
> "quirks in ppc and concerns in arm land" and is missing links to
> archived versions of v1 and v2), but clearly legacy resources are
> x86-specific so any code dealing with them seems superfluous on
> other arches and should be marked as such.

Quirk/v1: https://www.spinics.net/lists/linux-pci/msg62865.html
Approach 2: https://www.spinics.net/lists/linux-pci/msg63092.html
            https://www.spinics.net/lists/linux-pci/msg63083.html

The quirk in powerpc land that I'm referring to is
arch/powerpc/kernel/pci-common.c::fixup_vga() which is a class enable
hook that marks the first VGA device it comes across as default if the
arbiter has not marked one.

The arm concerns are ventaliated in the threads I linked - they boil
down to "why do we need the arbiter at all on platforms without legacy
resources? Can't we do this more simply?"

> Would it be feasible to just sprinkle some "if (IS_ENABLED(CONFIG_X86))"
> over the portions of vgaarb.c that deal with legacy resources?

Yes and no. That would disable the unnecessary chunks of the VGA
arbiter, but we then still have to figure out how to mark devices as
default if not with the arbiter.

Regards,
Daniel

>
> Thanks,
>
> Lukas

Patch hide | download patch | download mbox

diff --git a/arch/ia64/pci/fixup.c b/arch/ia64/pci/fixup.c
index 41caa99add51..b35d1cf4501a 100644
--- a/arch/ia64/pci/fixup.c
+++ b/arch/ia64/pci/fixup.c
@@ -5,7 +5,7 @@ 
 
 #include <linux/pci.h>
 #include <linux/init.h>
-#include <linux/vgaarb.h>
+#include <linux/vga_default.h>
 #include <linux/screen_info.h>
 
 #include <asm/machvec.h>
diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
index c95fdda3a2dc..6cfaec107374 100644
--- a/arch/powerpc/kernel/pci-common.c
+++ b/arch/powerpc/kernel/pci-common.c
@@ -31,7 +31,7 @@ 
 #include <linux/irq.h>
 #include <linux/vmalloc.h>
 #include <linux/slab.h>
-#include <linux/vgaarb.h>
+#include <linux/vga_default.h>
 
 #include <asm/processor.h>
 #include <asm/io.h>
diff --git a/arch/x86/pci/fixup.c b/arch/x86/pci/fixup.c
index 11e407489db0..b1254bc09a45 100644
--- a/arch/x86/pci/fixup.c
+++ b/arch/x86/pci/fixup.c
@@ -5,7 +5,7 @@ 
 #include <linux/delay.h>
 #include <linux/dmi.h>
 #include <linux/pci.h>
-#include <linux/vgaarb.h>
+#include <linux/vga_default.h>
 #include <asm/hpet.h>
 #include <asm/pci_x86.h>
 
diff --git a/arch/x86/video/fbdev.c b/arch/x86/video/fbdev.c
index 9fd24846d094..62cfa74ea86e 100644
--- a/arch/x86/video/fbdev.c
+++ b/arch/x86/video/fbdev.c
@@ -9,7 +9,7 @@ 
 #include <linux/fb.h>
 #include <linux/pci.h>
 #include <linux/module.h>
-#include <linux/vgaarb.h>
+#include <linux/vga_default.h>
 
 int fb_is_primary_device(struct fb_info *info)
 {
diff --git a/drivers/gpu/vga/Kconfig b/drivers/gpu/vga/Kconfig
index 29437eabe095..81d4105aecf6 100644
--- a/drivers/gpu/vga/Kconfig
+++ b/drivers/gpu/vga/Kconfig
@@ -1,3 +1,14 @@ 
+config VGA_DEFAULT
+	bool "VGA Default Device Support" if EXPERT
+	default y
+	depends on PCI
+	help
+	  Some programs find it helpful to know what VGA device is the default.
+	  On platforms like x86 this means the device used by the BIOS to show
+	  early boot messages. On other platforms this may be an arbitrary PCI
+	  graphics card. Select this to have a default device recorded within
+	  the kernel and exposed to userspace through sysfs.
+
 config VGA_ARB
 	bool "VGA Arbitration" if EXPERT
 	default y
@@ -22,6 +33,7 @@  config VGA_SWITCHEROO
 	depends on X86
 	depends on ACPI
 	select VGA_ARB
+	select VGA_DEFAULT
 	help
 	  Many laptops released in 2008/9/10 have two GPUs with a multiplexer
 	  to switch between them. This adds support for dynamic switching when
diff --git a/drivers/gpu/vga/Makefile b/drivers/gpu/vga/Makefile
index 14ca30b75d0a..1e30f90d40fb 100644
--- a/drivers/gpu/vga/Makefile
+++ b/drivers/gpu/vga/Makefile
@@ -1,2 +1,3 @@ 
 obj-$(CONFIG_VGA_ARB)  += vgaarb.o
+obj-$(CONFIG_VGA_DEFAULT) += vga_default.o
 obj-$(CONFIG_VGA_SWITCHEROO) += vga_switcheroo.o
diff --git a/drivers/gpu/vga/vga_default.c b/drivers/gpu/vga/vga_default.c
new file mode 100644
index 000000000000..f6fcb0eb1507
--- /dev/null
+++ b/drivers/gpu/vga/vga_default.c
@@ -0,0 +1,159 @@ 
+/*
+ * vga_default.c: What is the default/boot PCI VGA device?
+ *
+ * (C) Copyright 2005 Benjamin Herrenschmidt <benh@kernel.crashing.org>
+ * (C) Copyright 2007 Paulo R. Zanoni <przanoni@gmail.com>
+ * (C) Copyright 2007, 2009 Tiago Vignatti <vignatti@freedesktop.org>
+ * (C) Copyright 2017 Canonical Ltd. (Author: Daniel Axtens <dja@axtens.net>)
+ *
+ * (License from vgaarb.c)
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+/*
+ * What device should a graphics system draw to? In order of priority:
+ *
+ *  1) Any devices configured specifically by the user (think
+ *     xorg.conf).
+ *
+ *  2) If the platform has a concept of a boot device for early boot
+ *     messages (think BIOS displays on x86), that device.
+ *
+ *  3) If the platform does not have the concept of a boot device,
+ *     then we still want to pick something. For now, pick the first
+ *     PCI VGA device with a driver bound and with memory or I/O
+ *     control on.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/pci.h>
+#include <linux/init.h>
+
+#include <linux/vga_default.h>
+
+static struct pci_dev *vga_default;
+/*
+ * only go active after the late initcall so as not to interfere with
+ * the arbiter
+ */
+static bool vga_default_active = false;
+
+/**
+ * vga_default_device - return the default VGA device
+ *
+ * This can be defined by the platform. The default implementation
+ * is rather dumb and will probably only work properly on single
+ * vga card setups and/or x86 platforms.
+ *
+ * If your VGA default device is not PCI, you'll have to return
+ * NULL here. In this case, I assume it will not conflict with
+ * any PCI card. If this is not true, I'll have to define two archs
+ * hooks for enabling/disabling the VGA default device if that is
+ * possible. This may be a problem with real _ISA_ VGA cards, in
+ * addition to a PCI one. I don't know at this point how to deal
+ * with that card. Can theirs IOs be disabled at all ? If not, then
+ * I suppose it's a matter of having the proper arch hook telling
+ * us about it, so we basically never allow anybody to succeed a
+ * vga_get()...
+ */
+
+struct pci_dev *vga_default_device(void)
+{
+	return vga_default;
+}
+EXPORT_SYMBOL_GPL(vga_default_device);
+
+void vga_set_default_device(struct pci_dev *pdev)
+{
+	if (vga_default == pdev)
+		return;
+
+	pci_dev_put(vga_default);
+	vga_default = pci_dev_get(pdev);
+}
+
+static bool vga_default_try_device(struct pci_dev *pdev)
+{
+	u16 cmd;
+
+	/* Only deal with VGA class devices */
+	if ((pdev->class >> 8) != PCI_CLASS_DISPLAY_VGA)
+		return false;
+
+	/* Only deal with devices with drivers bound */
+	if (!pdev->driver)
+		return false;
+
+	/* Require I/O or memory control */
+	pci_read_config_word(pdev, PCI_COMMAND, &cmd);
+	if (!(cmd & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY)))
+		return false;
+
+	dev_info(&pdev->dev, "vga_default: setting as default device\n");
+	vga_set_default_device(pdev);
+	return true;
+}
+
+static int __init vga_default_init(void)
+{
+	struct pci_dev *pdev;
+
+	vga_default_active = true;
+
+	if (vga_default_device())
+		return 0;
+
+	pdev = NULL;
+	while ((pdev =
+		pci_get_subsys(PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID,
+			       PCI_ANY_ID, pdev)) != NULL) {
+		if (vga_default_try_device(pdev))
+			return 0;
+	}
+
+	return 0;
+}
+late_initcall(vga_default_init);
+
+/*
+ * A driver could be loaded much later than late_initcall, for example
+ * if it's in a module.
+ *
+ * We want to pick that up. However, we want to make sure this does
+ * not interfere with the arbiter - it should only activate if the
+ * arbiter has already had a chance to operate. To ensure this, we set
+ * vga_default_active in the late_initcall: as the vga arbiter is a
+ * subsys initcall, it is guaranteed to fire first.
+ */
+static void vga_default_enable_hook(struct pci_dev *pdev)
+{
+       if (!vga_default_active)
+	       return;
+
+       if (vga_default_device())
+               return;
+
+       vga_default_try_device(pdev);
+}
+DECLARE_PCI_FIXUP_CLASS_ENABLE(PCI_ANY_ID, PCI_ANY_ID,
+			       PCI_CLASS_DISPLAY_VGA, 8,
+			       vga_default_enable_hook)
diff --git a/drivers/gpu/vga/vga_switcheroo.c b/drivers/gpu/vga/vga_switcheroo.c
index 3cd153c6d271..6612ec7981b6 100644
--- a/drivers/gpu/vga/vga_switcheroo.c
+++ b/drivers/gpu/vga/vga_switcheroo.c
@@ -41,7 +41,7 @@ 
 #include <linux/pm_runtime.h>
 #include <linux/seq_file.h>
 #include <linux/uaccess.h>
-#include <linux/vgaarb.h>
+#include <linux/vga_default.h>
 #include <linux/vga_switcheroo.h>
 
 /**
diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c
index 76875f6299b8..74683286f5f8 100644
--- a/drivers/gpu/vga/vgaarb.c
+++ b/drivers/gpu/vga/vgaarb.c
@@ -51,6 +51,7 @@ 
 
 #include <linux/uaccess.h>
 
+#include <linux/vga_default.h>
 #include <linux/vgaarb.h>
 
 static void vga_arbiter_notify_clients(void);
@@ -119,9 +120,6 @@  static int vga_str_to_iostate(char *buf, int str_size, int *io_state)
 	return 1;
 }
 
-/* this is only used a cookie - it should not be dereferenced */
-static struct pci_dev *vga_default;
-
 static void vga_arb_device_card_gone(struct pci_dev *pdev);
 
 /* Find somebody in our list */
@@ -135,39 +133,6 @@  static struct vga_device *vgadev_find(struct pci_dev *pdev)
 	return NULL;
 }
 
-/**
- * vga_default_device - return the default VGA device, for vgacon
- *
- * This can be defined by the platform. The default implementation
- * is rather dumb and will probably only work properly on single
- * vga card setups and/or x86 platforms.
- *
- * If your VGA default device is not PCI, you'll have to return
- * NULL here. In this case, I assume it will not conflict with
- * any PCI card. If this is not true, I'll have to define two archs
- * hooks for enabling/disabling the VGA default device if that is
- * possible. This may be a problem with real _ISA_ VGA cards, in
- * addition to a PCI one. I don't know at this point how to deal
- * with that card. Can theirs IOs be disabled at all ? If not, then
- * I suppose it's a matter of having the proper arch hook telling
- * us about it, so we basically never allow anybody to succeed a
- * vga_get()...
- */
-struct pci_dev *vga_default_device(void)
-{
-	return vga_default;
-}
-EXPORT_SYMBOL_GPL(vga_default_device);
-
-void vga_set_default_device(struct pci_dev *pdev)
-{
-	if (vga_default == pdev)
-		return;
-
-	pci_dev_put(vga_default);
-	vga_default = pci_dev_get(pdev);
-}
-
 static inline void vga_irq_set_state(struct vga_device *vgadev, bool state)
 {
 	if (vgadev->irq_set_state)
@@ -667,7 +632,7 @@  static bool vga_arbiter_add_pci_device(struct pci_dev *pdev)
 	/* Deal with VGA default device. Use first enabled one
 	 * by default if arch doesn't have it's own hook
 	 */
-	if (vga_default == NULL &&
+	if (vga_default_device() == NULL &&
 	    ((vgadev->owns & VGA_RSRC_LEGACY_MASK) == VGA_RSRC_LEGACY_MASK)) {
 		vgaarb_info(&pdev->dev, "setting as boot VGA device\n");
 		vga_set_default_device(pdev);
@@ -704,7 +669,7 @@  static bool vga_arbiter_del_pci_device(struct pci_dev *pdev)
 		goto bail;
 	}
 
-	if (vga_default == pdev)
+	if (vga_default_device() == pdev)
 		vga_set_default_device(NULL);
 
 	if (vgadev->decodes & (VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM))
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 2f3780b50723..c174b427ea2b 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -27,7 +27,7 @@ 
 #include <linux/security.h>
 #include <linux/pci-aspm.h>
 #include <linux/slab.h>
-#include <linux/vgaarb.h>
+#include <linux/vga_default.h>
 #include <linux/pm_runtime.h>
 #include <linux/of.h>
 #include "pci.h"
diff --git a/include/linux/vga_default.h b/include/linux/vga_default.h
new file mode 100644
index 000000000000..78df6a2a194c
--- /dev/null
+++ b/include/linux/vga_default.h
@@ -0,0 +1,44 @@ 
+/*
+ * vga_default.h: What is the default/boot PCI VGA device?
+ *
+ * (C) Copyright 2005 Benjamin Herrenschmidt <benh@kernel.crashing.org>
+ * (C) Copyright 2007 Paulo R. Zanoni <przanoni@gmail.com>
+ * (C) Copyright 2007, 2009 Tiago Vignatti <vignatti@freedesktop.org>
+ * (C) Copyright 2017 Canonical Ltd. (Author: Daniel Axtens <dja@axtens.net>)
+ *
+ * (License from vgaarb.h)
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#ifndef LINUX_VGA_DEFAULT_H
+#define LINUX_VGA_DEFAULT_H
+
+struct pci_dev;
+
+#ifdef CONFIG_VGA_DEFAULT
+extern struct pci_dev *vga_default_device(void);
+extern void vga_set_default_device(struct pci_dev *pdev);
+#else
+static inline struct pci_dev *vga_default_device(void) { return NULL; };
+static inline void vga_set_default_device(struct pci_dev *pdev) { };
+#endif
+
+#endif
diff --git a/include/linux/vgaarb.h b/include/linux/vgaarb.h
index ee162e3e879b..953e1955efbe 100644
--- a/include/linux/vgaarb.h
+++ b/include/linux/vgaarb.h
@@ -42,12 +42,6 @@ 
 #define VGA_RSRC_NORMAL_IO     0x04
 #define VGA_RSRC_NORMAL_MEM    0x08
 
-/* Passing that instead of a pci_dev to use the system "default"
- * device, that is the one used by vgacon. Archs will probably
- * have to provide their own vga_default_device();
- */
-#define VGA_DEFAULT_DEVICE     (NULL)
-
 struct pci_dev;
 
 /* For use by clients */
@@ -122,14 +116,6 @@  extern void vga_put(struct pci_dev *pdev, unsigned int rsrc);
 #endif
 
 
-#ifdef CONFIG_VGA_ARB
-extern struct pci_dev *vga_default_device(void);
-extern void vga_set_default_device(struct pci_dev *pdev);
-#else
-static inline struct pci_dev *vga_default_device(void) { return NULL; };
-static inline void vga_set_default_device(struct pci_dev *pdev) { };
-#endif
-
 /*
  * Architectures should define this if they have several
  * independent PCI domains that can afford concurrent VGA