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Subject[PATCH v8 04/10] vgaarb: Move framebuffer detection to ADD_DEVICE path
Date
From: Bjorn Helgaas <bhelgaas@google.com>

Previously we selected a device that owns the boot framebuffer as the
default device in vga_arb_select_default_device(). This was only done in
the vga_arb_device_init() subsys_initcall, so devices enumerated later,
e.g., by pcibios_init(), were not eligible.

Fix this by moving the framebuffer 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.

Note that if vga_arb_select_default_device() found a device owning the boot
framebuffer, it unconditionally set it to be the default VGA device, and no
subsequent device could replace it.

Link: https://lore.kernel.org/r/20211015061512.2941859-7-chenhuacai@loongson.cn
Based-on-patch-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Bruno Prémont <bonbons@linux-vserver.org>
---
drivers/gpu/vga/vgaarb.c | 37 +++++++++++++++++--------------------
1 file changed, 17 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c
index b0ae0f177c6f..aefa4f406f7d 100644
--- a/drivers/gpu/vga/vgaarb.c
+++ b/drivers/gpu/vga/vgaarb.c
@@ -72,6 +72,7 @@ struct vga_device {
unsigned int io_norm_cnt; /* normal IO count */
unsigned int mem_norm_cnt; /* normal MEM count */
bool bridge_has_one_vga;
+ bool is_framebuffer; /* BAR covers firmware framebuffer */
unsigned int (*set_decode)(struct pci_dev *pdev, bool decode);
};

@@ -565,10 +566,9 @@ void vga_put(struct pci_dev *pdev, unsigned int rsrc)
}
EXPORT_SYMBOL(vga_put);

-static void __init vga_select_framebuffer_device(struct pci_dev *pdev)
+static bool vga_is_framebuffer_device(struct pci_dev *pdev)
{
#if defined(CONFIG_X86) || defined(CONFIG_IA64)
- struct device *dev = &pdev->dev;
u64 base = screen_info.lfb_base;
u64 size = screen_info.lfb_size;
u64 limit;
@@ -583,15 +583,6 @@ static void __init vga_select_framebuffer_device(struct pci_dev *pdev)

limit = base + size;

- /*
- * Override vga_arbiter_add_pci_device()'s I/O based detection
- * as it may take the wrong device (e.g. on Apple system under
- * EFI).
- *
- * Select the device owning the boot framebuffer if there is
- * one.
- */
-
/* Does firmware framebuffer belong to us? */
for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {
flags = pci_resource_flags(pdev, i);
@@ -608,13 +599,10 @@ static void __init vga_select_framebuffer_device(struct pci_dev *pdev)
if (base < start || limit >= end)
continue;

- if (!vga_default_device())
- vgaarb_info(dev, "setting as boot device\n");
- else if (pdev != vga_default_device())
- vgaarb_info(dev, "overriding boot device\n");
- vga_set_default_device(pdev);
+ return true;
}
#endif
+ return false;
}

static bool vga_arb_integrated_gpu(struct device *dev)
@@ -635,6 +623,7 @@ static bool vga_arb_integrated_gpu(struct device *dev)
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;

/*
* We select the default VGA device in this order:
@@ -645,6 +634,18 @@ static bool vga_is_boot_device(struct vga_device *vgadev)
* Other device (see vga_arb_select_default_device())
*/

+ /*
+ * We always prefer a firmware framebuffer, so if we've already
+ * found one, there's no need to consider vgadev.
+ */
+ if (boot_vga && boot_vga->is_framebuffer)
+ return false;
+
+ if (vga_is_framebuffer_device(pdev)) {
+ vgadev->is_framebuffer = true;
+ return true;
+ }
+
/*
* A legacy VGA device has MEM and IO enabled and any bridges
* leading to it have PCI_BRIDGE_CTL_VGA enabled so the legacy
@@ -1531,10 +1532,6 @@ static void __init vga_arb_select_default_device(void)
struct pci_dev *pdev, *found = NULL;
struct vga_device *vgadev;

- list_for_each_entry(vgadev, &vga_list, list) {
- vga_select_framebuffer_device(vgadev->pdev);
- }
-
if (!vga_default_device()) {
list_for_each_entry_reverse(vgadev, &vga_list, list) {
struct device *dev = &vgadev->pdev->dev;
--
2.25.1
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