[PATCH v2 1/1] Split VGA default device handler out of VGA arbiter
Lorenzo Pieralisi
lorenzo.pieralisi at arm.com
Mon Aug 21 20:53:01 AEST 2017
On Thu, Aug 17, 2017 at 09:30:28PM +1000, Daniel Axtens wrote:
> A system without PCI legacy resources (e.g. ARM64) 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.
I do not understand this paragraph, in particular:
- "A system without PCI legacy resources (e.g. ARM64)". What does this
mean ? I take this as "ARM64 does not support IO space"; if a PCI host
bridge supports IO space, there is nothing from an architectural
point of view that prevents an MMIO based IO space implementation to
work on ARM64. It is PCI bridge specific, not arch specific.
- "the VGA arbiter checks for legacy resources". Do you mean it checks
if a VGA class device enabled IO/MEM address spaces (and if the
bridges upstream forwards those address spaces), correct ?
The assumption relying on ARM64 not supporting IO space (if that's what
you mean by "a system without PCI legacy resources") is not correct.
Thanks,
Lorenzo
> 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.
>
> 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 at axtens.net>
>
> ---
>
> v2: Tested on:
> - x86_64 laptop
> - arm64 D05 board with hibmc card
> - qemu powerpc with tcg and bochs std-vga
>
> 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
>
> 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 341a7469cab8..4fd890a51d18 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 at kernel.crashing.org>
> + * (C) Copyright 2007 Paulo R. Zanoni <przanoni at gmail.com>
> + * (C) Copyright 2007, 2009 Tiago Vignatti <vignatti at freedesktop.org>
> + * (C) Copyright 2017 Canonical Ltd. (Author: Daniel Axtens <dja at 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 at kernel.crashing.org>
> + * (C) Copyright 2007 Paulo R. Zanoni <przanoni at gmail.com>
> + * (C) Copyright 2007, 2009 Tiago Vignatti <vignatti at freedesktop.org>
> + * (C) Copyright 2017 Canonical Ltd. (Author: Daniel Axtens <dja at 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
> --
> 2.11.0
>
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