On Wed, 24 Jul 2024 at 18:27, Aditya Garg <gargaditya08@xxxxxxxx> wrote: > > > > > On 24 Jul 2024, at 9:31 PM, Lukas Wunner <lukas@xxxxxxxxx> wrote: > > > > On Tue, Jul 23, 2024 at 04:25:19PM +0000, Aditya Garg wrote: > >>> On Wed, Jul 17, 2024 at 04:35:15PM +0000, Aditya Garg wrote: > >>> For the Macs having a single GPU, in case a person uses an eGPU, > >>> they still need this apple-set-os quirk for hybrid graphics. > >> > >> Sending this message again as for some reason it got sent only to Lukas: > >> > >> Full model name: Mac mini (2018) (Macmini8,1) > >> > >> The drive link below has the logs: > >> > >> https://drive.google.com/file/d/1P3-GlksU6WppvzvWC0A-nAoTZh7oPPxk/view?usp=drive_link > > > > Some observations: > > > > * dmesg-with-egpu.txt: It seems the system was actually booted *without* > > an eGPU, so the filename appears to be a misnomer. > > > > * The two files in the with_apple_set_os_efi directory only contain > > incomplete dmesg output. Boot with log_buf_len=16M to solve this. > > Fortunately the truncated log is sufficient to see what's going on. > > > > * If the apple_set_os protocol is not used, the attached eGPU is not > > enumerated by the kernel on boot and a rescan is required. > > So neither the iGPU nor the eGPU are working. The reason is BIOS > > sets up incorrect bridge windows for the Thunderbolt host controller: > > Its two downstream ports' 64-bit windows overlap. The 32-bit windows > > do not overlap. If apple_set_os is used, the eGPU is using the > > (non-overlapping) 32-bit window. If apple_set_os is not used, > > the attached eGPU is using the (overlapping, hence broken) 64-bit window. > > > > So not only is apple_set_os needed to keep the iGPU enabled, > > but also to ensure BIOS sets up bridge windows in a manner that is > > only halfway broken and not totally broken. > > > > Below, 0000:06:01.0 and 0000:06:04.0 are the downstream ports on the > > Thunderbolt host controller and 0000:09:00.0 is the upstream port of > > the attached eGPU. > > > > iGPU enabled, no eGPU attached (dmesg.txt): > > pci 0000:06:01.0: bridge window [mem 0x81900000-0x888fffff] > > pci 0000:06:01.0: bridge window [mem 0xb1400000-0xb83fffff 64bit pref] > > pci 0000:06:04.0: bridge window [mem 0x88900000-0x8f8fffff] > > pci 0000:06:04.0: bridge window [mem 0xb8400000-0xbf3fffff 64bit pref] > > > > iGPU disabled, eGPU attached, apple_set_os not used (journalctl.txt): > > pci 0000:06:01.0: bridge window [mem 0x81900000-0x888fffff] > > pci 0000:06:01.0: bridge window [mem 0xb1400000-0xc6ffffff 64bit pref] > > pci 0000:06:04.0: bridge window [mem 0x88900000-0x8f8fffff] > > pci 0000:06:04.0: bridge window [mem 0xb8400000-0xbf3fffff 64bit pref] > > pci 0000:06:04.0: bridge window [mem 0xb8400000-0xbf3fffff 64bit pref]: can't claim; address conflict with PCI Bus 0000:09 [mem 0xb1400000-0xbf3fffff 64bit pref] > > > > iGPU enabled, eGPU attached, apple_set_os used (working-journalctl.txt): > > pci 0000:06:01.0: bridge window [mem 0x81900000-0x888fffff] > > pci 0000:06:01.0: bridge window [mem 0xb1400000-0xc6ffffff 64bit pref] > > pci 0000:06:04.0: bridge window [mem 0x88900000-0x8f8fffff] > > pci 0000:06:04.0: bridge window [mem 0xb8400000-0xbf3fffff 64bit pref] > > pci 0000:09:00.0: bridge window [mem 0x81900000-0x81cfffff] > > > > * As to how we can solve this and keep using apple_set_os only when > > necessary: > > > > I note that on x86, the efistub walks over all PCI devices in the system > > (see setup_efi_pci() in drivers/firmware/efi/libstub/x86-stub.c) and > > retrieves the Device ID and Vendor ID. We could additionally retrieve > > the Class Code and count the number of GPUs in the system by checking > > whether the Class Code matches PCI_BASE_CLASS_DISPLAY. If there's > > at least 2 GPUs in the system, invoke apple_set_os. > > This also looks like a good idea, but I'm not well aware of the pci quirks in the Linux kernel. So, would consider it a bug report for the maintainers to fix. That is not how it works. This is not a regression in Linux, and even if it was, it is not the maintainers' job to fix bugs. If Linux is lacking functionality that you find important, please propose a patch the implements it, and argue why it should be merged.
