Re: Fwd: USB DBC hang during earlyprintk initialization

[Mathias Nyman <mathias.nyman@linux.intel.com>]

On 10/15/25 22:11, Milan Oravec wrote:
> Hello Greg,
> thank you for looking into it.
> 
> On Wed, Oct 15, 2025 at 11:13 AM Greg KH <gregkh@linuxfoundation.org> wrote:
>>
>> On Wed, Oct 15, 2025 at 09:43:02AM +0200, Milan Oravec wrote:
>>> Hello, I'm trying to debug some hibernation related problems on my
>>> system, and need a USB DBC to see what is going on after screen off.
>>> I've connected USB debugging cable and got this error:
> > [St okt 15 20:57:24 2025] Linux version 6.17.3 (migo@migoG17) (gcc
> (GCC) 15.2.1 20250813, GNU ld (GNU Binutils) 2.45.0) #55 SMP
> PREEMPT_DYNAMIC Wed Oct 15 19:24:41 CEST 2025
> [St okt 15 20:57:24 2025] Command line: BOOT_IMAGE=/vmlinuz
> root=UUID=584262b6-b020-4e4f-95a3-1db754e28b6c earlyprintk=keep,xdbc1
> debug ignore_loglevel sysrq_always_enabled
> force_early_printk sched_verbose ft usbcore.autosuspend=-1
> no_console_suspend hib_compression=lz4
> resume=UUID=54ed98b5-56c0-4ab9-95ea-da1a9322ce49
> [St okt 15 20:57:24 2025] BIOS-provided physical RAM map:
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x0000000000000000-0x000000000009ffff] usable
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x00000000000a0000-0x00000000000fffff] reserved
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x0000000000100000-0x0000000009afefff] usable
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x0000000009aff000-0x0000000009ffffff] reserved
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x000000000a000000-0x000000000a1fffff] usable
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x000000000a200000-0x000000000a211fff] ACPI NVS
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x000000000a212000-0x000000008e43dfff] usable
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x000000008e43e000-0x000000009443dfff] reserved
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x000000009443e000-0x000000009453dfff] ACPI data
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x000000009453e000-0x000000009653dfff] ACPI NVS
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x000000009653e000-0x000000009a5fefff] reserved
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x000000009a5ff000-0x000000009bffafff] usable
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x000000009bffb000-0x000000009cffffff] reserved
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x000000009d7f3000-0x000000009fffffff] reserved
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x00000000f0000000-0x00000000f7ffffff] reserved
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x00000000fd000000-0x00000000ffffffff] reserved
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x0000000100000000-0x0000000837ffffff] usable
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x0000000838000000-0x0000000857ffffff] reserved
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x0000000858000000-0x000000085de7ffff] usable
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x000000085eec0000-0x00000008801fffff] reserved
> [St okt 15 20:57:24 2025] BIOS-e820: [mem
> 0x000000fd00000000-0x000000ffffffffff] reserved
> [St okt 15 20:57:24 2025] xhci_dbc:early_xdbc_parse_parameter: dbgp_num: 1
> [St okt 15 20:57:24 2025] ------------[ cut here ]------------
> [St okt 15 20:57:24 2025] WARNING: CPU: 0 PID: 0 at
> mm/early_ioremap.c:139 __early_ioremap+0xae/0x190

This WARN in __early_ioremap() is triggered when the size is too large

	/*
	 * Mappings have to fit in the FIX_BTMAP area.
	 */
	nrpages = size >> PAGE_SHIFT;
	if (WARN_ON(nrpages > NR_FIX_BTMAPS))
		return NULL;

The size is in this case read from the PCI config space of the second xHCI PCI
controller.

Maybe the controller returns odd BAR Address0 size, or we parse it incorrectly.

what does "lspci -vv -d ::0c03:30" show?

Thanks
Mathias