Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider: - [High] PCI/VGA: pci_fixup_vgadev() overrides vga_is_firmware_default() on LoongArch - [Medium] PCI/VGA: duplicate non-idempotent screen_info_apply_fixups() call on LoongArch - [Medium] PCI/VGA: vga_is_firmware_default() fails to match Loongson integrated DC --
commit 6de860408bce3c5a20f5a4c23b073eafdc942117 Author: wuqianhai <[email protected]> PCI/VGA: Enable firmware default device detection on LoongArch This commit enables vga_is_firmware_default() on LoongArch, selects CONFIG_SYSFB from CONFIG_VGA_ARB for LoongArch, and calls screen_info_apply_fixups() in vga_arb_device_init() so relocated firmware framebuffer BARs can be matched when selecting the default boot VGA device. > diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c > index 3e58b2c05c854..1b7e915629f97 100644 > --- a/drivers/pci/vgaarb.c > +++ b/drivers/pci/vgaarb.c > @@ -566,7 +566,7 @@ EXPORT_SYMBOL(vga_put); > > static bool vga_is_firmware_default(struct pci_dev *pdev) > { > -#if defined CONFIG_X86 > +#if defined(CONFIG_X86) || defined(CONFIG_LOONGARCH) > return pdev == screen_info_pci_dev(&sysfb_primary_display.screen); [Severity: High] On LoongArch systems with a Loongson display controller (PCI device IDs 0x7a06, 0x7a36, or 0x7a46) and one or more discrete VGA devices, will pci_fixup_vgadev() in arch/loongarch/pci/pci.c later overwrite the firmware default VGA device selected here? During ACPI boot on LoongArch, PCI enumeration runs in subsys_initcall(acpi_init), and vga_arb_device_init() runs next at subsys_initcall_sync: vga_arb_device_init() vga_arbiter_add_pci_device() vga_is_boot_device() vga_is_firmware_default() vga_set_default_device(pdev) After vga_arb_device_init() finishes, pci_apply_final_quirks() in drivers/pci/quirks.c runs at fs_initcall_sync and invokes the DECLARE_PCI_FIXUP_FINAL hooks in arch/loongarch/pci/pci.c: static void pci_fixup_vgadev(struct pci_dev *pdev) { struct pci_dev *devp = NULL; while ((devp = pci_get_class(PCI_CLASS_DISPLAY_VGA << 8, devp))) { if (devp->vendor != PCI_VENDOR_ID_LOONGSON) { vga_set_default_device(devp); dev_info(&pdev->dev, "Overriding boot device as %X:%X\n", devp->vendor, devp->device); } } } DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LOONGSON, PCI_DEVICE_ID_LOONGSON_DC1, pci_fixup_vgadev); DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LOONGSON, PCI_DEVICE_ID_LOONGSON_DC2, pci_fixup_vgadev); DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LOONGSON, PCI_DEVICE_ID_LOONGSON_DC3, pci_fixup_vgadev); Because pci_fixup_vgadev() unconditionally calls vga_set_default_device(devp) for every non-Loongson VGA device without checking whether a firmware default device was already chosen, won't it clobber vga_default whenever firmware selected a Loongson display device or the first of multiple non-Loongson discrete GPUs as the primary display? [Severity: Medium] Also in vga_is_firmware_default() in drivers/pci/vgaarb.c, can this pointer comparison ever match when the firmware framebuffer resides on Loongson integrated graphics (such as on LS7A1000, LS7A2000, or LS2K2000)? As shown in lsdc_get_dedicated_vram() in drivers/gpu/drm/loongson/lsdc_drv.c, the integrated graphics subsystem is split across two PCI functions: /* * The GPU has 00:06.0 as its BDF, while the DC has 00:06.1 * This is true for the LS7A1000, LS7A2000 and LS2K2000. */ pdev_gpu = pci_get_domain_bus_and_slot(pci_domain_nr(pdev_dc->bus), pdev_dc->bus->number, PCI_DEVFN(6, 0)); ... base = pci_resource_start(pdev_gpu, 2); size = pci_resource_len(pdev_gpu, 2); When the firmware framebuffer is placed in integrated VRAM, screen_info_pci_dev(&sysfb_primary_display.screen) matches BAR 2 of the companion GPU device at 00:06.0 (PCI_DEVICE_ID_LOONGSON_GPU1/2/3). However, vga_arb_device_init() and pci_notify() filter devices using pci_is_vga(pdev), so only the VGA-class Display Controller function at 00:06.1 (PCI_DEVICE_ID_LOONGSON_DC1/2/3, whose BAR 0 only maps MMIO registers) is passed to vga_is_firmware_default(pdev). Doesn't comparing pdev (00:06.1) against screen_info_pci_dev() (00:06.0) always evaluate to false for the integrated display controller? > #else > return false; > @@ -1527,6 +1527,16 @@ static int __init vga_arb_device_init(void) > int rc; > struct pci_dev *pdev; > > +#if defined(CONFIG_LOONGARCH) > + /* > + * On LoongArch, PCI resource assignment completes during > + * subsys_initcall (acpi_init), before the VGA arbiter runs. Refresh > + * screen_info so vga_is_firmware_default() can match the relocated > + * BAR. > + */ > + screen_info_apply_fixups(); > +#endif [Severity: Medium] With CONFIG_VGA_ARB selecting CONFIG_SYSFB on LoongArch, calling screen_info_apply_fixups() here in vga_arb_device_init() at subsys_initcall_sync means screen_info_apply_fixups() will be called a second time when sysfb_init() in drivers/firmware/sysfb.c runs at device_initcall: drivers/firmware/sysfb.c:sysfb_init() { ... screen_info_apply_fixups(); mutex_lock(&disable_lock); if (disabled) goto unlock_mutex; ... } Looking at screen_info_apply_fixups() in drivers/video/screen_info_pci.c: void screen_info_apply_fixups(void) { struct screen_info *si = &sysfb_primary_display.screen; if (screen_info_lfb_pdev) { struct resource *pr = &screen_info_lfb_pdev->resource[screen_info_lfb_bar]; if (pr->start != screen_info_lfb_res_start) { if (__screen_info_relocation_is_valid(si, pr)) { __screen_info_set_lfb_base(si, pr->start + screen_info_lfb_offset); pr_info("Relocating firmware framebuffer to offset %pa[d] within %pr\n", &screen_info_lfb_offset, pr); } else { pr_warn("Invalid relocating, disabling firmware framebuffer\n"); } } } } Because screen_info_apply_fixups() neither updates screen_info_lfb_res_start nor clears screen_info_lfb_pdev after applying the fixup, won't the second call in sysfb_init() re-run the relocation logic and print a duplicate message whenever the framebuffer BAR was relocated, or emit a spurious warning if a built-in GPU driver probed earlier in device_initcall and resized the BAR after calling sysfb_disable()? -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=1
