From: Bjorn Helgaas <helgaas@kernel.org>
To: David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>
Cc: Xuefeng Li <lixuefeng@loongson.cn>,
Huacai Chen <chenhuacai@gmail.com>,
Huacai Chen <chenhuacai@loongson.cn>,
linux-pci@vger.kernel.org, dri-devel@lists.freedesktop.org,
linux-kernel@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>,
Huacai Chen <chenhuacai@kernel.org>,
Daniel Axtens <dja@axtens.net>,
Zhou Wang <wangzhou1@hisilicon.com>
Subject: [PATCH v8 05/10] vgaarb: Move non-legacy VGA detection to ADD_DEVICE path
Date: Wed, 5 Jan 2022 18:06:53 -0600 [thread overview]
Message-ID: <20220106000658.243509-6-helgaas@kernel.org> (raw)
In-Reply-To: <20220106000658.243509-1-helgaas@kernel.org>
From: Bjorn Helgaas <bhelgaas@google.com>
a37c0f48950b ("vgaarb: Select a default VGA device even if there's no
legacy VGA") extended the vga_arb_device_init() subsys_initcall so it could
select a non-legacy VGA device as the default.
That failed to consider that PCI devices may be enumerated after
vga_arb_device_init(), e.g., hot-added devices or non-ACPI systems that do
PCI enumeration in pcibios_init(). Devices found then could never be
selected as the default.
One system where this is a problem is the MIPS-based Loongson where an
ASpeed AST2500 VGA device is behind a bridge that doesn't implement the VGA
Enable bit, so legacy resources are not routed to the VGA device. [1]
Fix this by moving the non-legacy VGA device selection from
vga_arb_select_default_device() to vga_arbiter_add_pci_device(), which is
called after every PCI device is enumerated, either by the
vga_arb_device_init() subsys_initcall or as an ADD_DEVICE notifier.
[1] https://lore.kernel.org/r/20210514080025.1828197-6-chenhuacai@loongson.cn
Link: https://lore.kernel.org/r/20211015061512.2941859-5-chenhuacai@loongson.cn
Link: https://lore.kernel.org/r/20211015061512.2941859-7-chenhuacai@loongson.cn
Based-on-patch-by: Huacai Chen <chenhuacai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Daniel Axtens <dja@axtens.net>
Cc: Zhou Wang <wangzhou1@hisilicon.com>
---
drivers/gpu/vga/vgaarb.c | 54 ++++++++++++++++++++++++----------------
1 file changed, 32 insertions(+), 22 deletions(-)
diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c
index aefa4f406f7d..123b81628061 100644
--- a/drivers/gpu/vga/vgaarb.c
+++ b/drivers/gpu/vga/vgaarb.c
@@ -624,6 +624,7 @@ static bool vga_is_boot_device(struct vga_device *vgadev)
{
struct vga_device *boot_vga = vgadev_find(vga_default_device());
struct pci_dev *pdev = vgadev->pdev;
+ u16 cmd, boot_cmd;
/*
* We select the default VGA device in this order:
@@ -661,6 +662,37 @@ static bool vga_is_boot_device(struct vga_device *vgadev)
if ((vgadev->owns & VGA_RSRC_LEGACY_MASK) == VGA_RSRC_LEGACY_MASK)
return true;
+ /*
+ * If we haven't found a legacy VGA device, accept a non-legacy
+ * device. It may have either IO or MEM enabled, and bridges may
+ * not have PCI_BRIDGE_CTL_VGA enabled, so it may not be able to
+ * use legacy VGA resources. Prefer an integrated GPU over others.
+ */
+ pci_read_config_word(pdev, PCI_COMMAND, &cmd);
+ if (cmd & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY)) {
+
+ /*
+ * An integrated GPU overrides a previous non-legacy
+ * device. We expect only a single integrated GPU, but if
+ * there are more, we use the *last* because that was the
+ * previous behavior.
+ */
+ if (vga_arb_integrated_gpu(&pdev->dev))
+ return true;
+
+ /*
+ * We prefer the first non-legacy discrete device we find.
+ * If we already found one, vgadev is no better.
+ */
+ if (boot_vga) {
+ pci_read_config_word(boot_vga->pdev, PCI_COMMAND,
+ &boot_cmd);
+ if (boot_cmd & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY))
+ return false;
+ }
+ return true;
+ }
+
return false;
}
@@ -1529,30 +1561,8 @@ static struct miscdevice vga_arb_device = {
static void __init vga_arb_select_default_device(void)
{
- struct pci_dev *pdev, *found = NULL;
struct vga_device *vgadev;
- if (!vga_default_device()) {
- list_for_each_entry_reverse(vgadev, &vga_list, list) {
- struct device *dev = &vgadev->pdev->dev;
- u16 cmd;
-
- pdev = vgadev->pdev;
- pci_read_config_word(pdev, PCI_COMMAND, &cmd);
- if (cmd & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY)) {
- found = pdev;
- if (vga_arb_integrated_gpu(dev))
- break;
- }
- }
- }
-
- if (found) {
- vgaarb_info(&found->dev, "setting as boot device (VGA legacy resources not available)\n");
- vga_set_default_device(found);
- return;
- }
-
if (!vga_default_device()) {
vgadev = list_first_entry_or_null(&vga_list,
struct vga_device, list);
--
2.25.1
next prev parent reply other threads:[~2022-01-06 0:07 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-06 0:06 [PATCH v8 00/10] vgaarb: Rework default VGA device selection Bjorn Helgaas
2022-01-06 0:06 ` [PATCH v8 01/10] vgaarb: Move vga_arb_integrated_gpu() earlier in file Bjorn Helgaas
2022-01-06 0:06 ` [PATCH v8 02/10] vgaarb: Factor out vga_select_framebuffer_device() Bjorn Helgaas
2022-01-06 0:06 ` [PATCH v8 03/10] vgaarb: Factor out default VGA device selection Bjorn Helgaas
2022-01-06 0:06 ` [PATCH v8 04/10] vgaarb: Move framebuffer detection to ADD_DEVICE path Bjorn Helgaas
2022-01-06 6:44 ` Huacai Chen
2022-01-06 16:20 ` Bjorn Helgaas
2022-01-25 2:51 ` Huacai Chen
2022-01-25 15:38 ` Bjorn Helgaas
2022-01-26 2:25 ` Huacai Chen
2022-01-06 0:06 ` Bjorn Helgaas [this message]
2022-01-06 0:06 ` [PATCH v8 06/10] vgaarb: Move disabled VGA device " Bjorn Helgaas
2022-01-06 0:06 ` [PATCH v8 07/10] vgaarb: Remove empty vga_arb_device_card_gone() Bjorn Helgaas
2022-01-06 0:06 ` [PATCH v8 08/10] vgaarb: Log bridge control messages when adding devices Bjorn Helgaas
2022-01-06 0:06 ` [PATCH v8 09/10] vgaarb: Use unsigned format string to print lock counts Bjorn Helgaas
2022-01-06 0:06 ` [PATCH v8 10/10] vgaarb: Replace full MIT license text with SPDX identifier Bjorn Helgaas
2022-01-06 16:30 ` [PATCH v8 00/10] vgaarb: Rework default VGA device selection Bjorn Helgaas
2022-01-08 3:26 ` Huacai Chen
2022-01-31 22:23 ` Bjorn Helgaas
2022-02-01 15:46 ` Maarten Lankhorst
2022-02-07 17:59 ` Bjorn Helgaas
2022-02-08 2:14 ` Huacai Chen
2022-02-14 16:19 ` Bjorn Helgaas
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