From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from fanzine2.igalia.com (fanzine2.igalia.com [213.97.179.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3DE1333A032; Wed, 20 May 2026 12:54:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.97.179.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779281697; cv=none; b=Pu0qxGupNF24BegZ9HLjdem5L4sfT9pcycq21cgbNyb853a0wj6l1GMaTHif5VmJbCk6sgUSg4QwW3MGm0v5Yr19SJbimD9utueQQrndRyHwLo+X0fOqtigjwcrVfo/4GvKzGc4TkcacYLzJyscn/1WWAYAa/Tg+yi6HDCxeLLY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779281697; c=relaxed/simple; bh=45ij5qVAtYd5ZZF0L2p1N4BhNc9P6McUYfmny33QDMw=; h=MIME-Version:Date:From:To:Cc:Subject:In-Reply-To:References: Message-ID:Content-Type; b=ups8GQ11h8s3k0EiTCb/hUtFJOacwKNZGguUutORH6A9TxYpRxfe7CWcRBnjilYnvWmVopo69MSBVD6xRAwUK9O1vpVyH37UWAnJW6ahCIsIbGpiANhWL8/Vb41rZqeuqnv5nT/BtaPd5uZl7ZUVS0fDEtsMCj1g3oCneOUYbTw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com; spf=pass smtp.mailfrom=igalia.com; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b=CPMiPABG; arc=none smtp.client-ip=213.97.179.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=igalia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b="CPMiPABG" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:Content-Type:Message-ID:References: In-Reply-To:Subject:Cc:To:From:Date:MIME-Version:Sender:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=Mk2e1oeJq8p0n04P90LtVXvOIUOONjx8hxrYg+0UT9o=; b=CPMiPABGOeuocLIec6CY1JXSHL 2ARttKN1ljp1wGlapTf5JPmVNl/l4yiFbd3tyxUTpZMdEMDzTXiWwS78pazoFuBciWIqHNRpkbi+y QEX0vwvcNowFOO853NxOuW7KXzuvd2dsNxt6g9mbmp243Rw6E//htfdx1q6ZwxKV4TlS5Qqb4KaAF LhL2g6AZeb1Ek+ExSeEantc2jDDIViFGNZTOoAhq4DwqkhrAwXoN37EwHY6UZ6xB7WsX7eUR9ngDC T9Qt/TTeQidVwifbOv3iI/+xTaPX7IjYJRbfQ3Gm5Ehw0zB/faqcEyNWckstMhtNfeOMs2dCRf+vI nqD+Bu1Q==; Received: from maestria.local.igalia.com ([192.168.10.14] helo=mail.igalia.com) by fanzine2.igalia.com with esmtps (Cipher TLS1.3:ECDHE_SECP256R1__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim) id 1wPgRi-003pQx-5A; Wed, 20 May 2026 14:54:46 +0200 Received: from webmail.service.igalia.com ([192.168.21.45]) by mail.igalia.com with esmtp (Exim) id 1wPgRf-007pOJ-Qi; Wed, 20 May 2026 14:54:46 +0200 Received: from localhost ([127.0.0.1] helo=webmail.igalia.com) by webmail.service.igalia.com with esmtp (Exim 4.98.2) (envelope-from ) id 1wPgRf-00000002jWN-0ZI6; Wed, 20 May 2026 14:54:43 +0200 Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Wed, 20 May 2026 12:54:43 +0000 From: Umang Jain To: Greg Kroah-Hartman Cc: Lucas De Marchi , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-dev@igalia.com Subject: Re: [PATCH] usb: early: xhci-dbc: Ensure correct memory size for early_ioremap() In-Reply-To: <2026052001-regally-dizziness-2271@gregkh> References: <20260520094804.2981960-1-uajain@igalia.com> <2026052001-ruined-pesticide-9de7@gregkh> <81d706a4d1977ed39529336b2a8bc15f@igalia.com> <2026052001-regally-dizziness-2271@gregkh> Message-ID: <329c3970d932c21ca0ead6a84e573bd2@igalia.com> X-Sender: uajain@igalia.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Spam-Report: NO, Score=-4.7, Tests=ALL_TRUSTED=-3,AWL=-2.550,BAYES_50=0.8,URIBL_DBL_BLOCKED_OPENDNS=0.001,URIBL_ZEN_BLOCKED_OPENDNS=0.001 X-Spam-Score: -46 X-Spam-Bar: ---- On 2026-05-20 12:42, Greg Kroah-Hartman wrote: > On Wed, May 20, 2026 at 12:27:39PM +0000, Umang Jain wrote: >> Hi Greg, >> >> On 2026-05-20 11:22, Greg Kroah-Hartman wrote: >> > On Wed, May 20, 2026 at 03:18:04PM +0530, Umang Jain wrote: >> >> early_ioremap() checks and fail, if the memory size exceeds the fixed >> >> boot-time mappings (dictated by NR_FIX_BTMAPS macro). We should ensure >> >> the correct maximum memory size is passed to early_ioremap() in the >> >> driver. >> >> >> >> Without this check and page size being 4K(4096), enabling xhci-dbc >> >> on steamdeck seems to issue the warning: >> >> >> >> steamdeck kernel: xhci_dbc:early_xdbc_parse_parameter: dbgp_num: 0 >> >> steamdeck kernel: ------------[ cut here ]------------ >> >> ay 19 13:42:57 steamdeck kernel: WARNING: CPU: 0 PID: 0 at mm/early_ioremap.c:139 __early_ioremap+0xae/0x180 >> >> steamdeck kernel: Modules linked in: >> >> steamdeck kernel: CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.18.25-valve1-gcab630e7af50 #13 PREEMPT(undef) 4b70872d9de6788b7f2d10dce46ada89e6cd177b >> >> steamdeck kernel: RIP: 0010:__early_ioremap+0xae/0x180 >> >> steamdeck kernel: Code: 60 ba 3f a0 4c 89 ca 48 81 e3 00 f0 ff ff 48 81 e2 00 f0 ff ff 48 29 d3 48 89 14 24 48 89 da 48 c1 ea 0c 89 d5 83 fa 40 76 04 <0f> 0b eb a2 6b c0 c0 4d 89 ce 41 81 e6 ff 0f 00 00 44 8d b8 ff 05 >> >> steamdeck kernel: RSP: 0000:ffffffff9fa03cb8 EFLAGS: 00010006 ORIG_RAX: 0000000000000000 >> >> steamdeck kernel: RAX: 0000000000000000 RBX: 0000000000100000 RCX: 0000000000100000 >> >> steamdeck kernel: RDX: 0000000000000100 RSI: 0000000000100000 RDI: 0000000080200000 >> >> steamdeck kernel: RBP: 0000000000000100 R08: 0000000000000000 R09: 0000000080200000 >> >> steamdeck kernel: R10: 0000000000000004 R11: ffffffff9fa03ad0 R12: 8000000000000163 >> >> steamdeck kernel: R13: 0000000000000000 R14: 0000000080200000 R15: 0000000000000000 >> >> steamdeck kernel: FS: 0000000000000000(0000) GS:0000000000000000(0000) knlGS:0000000000000000 >> >> steamdeck kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> >> steamdeck kernel: CR2: ffff888000000413 CR3: 000000020ed02000 CR4: 00000000000000b0 >> >> steamdeck kernel: Call Trace: >> >> steamdeck kernel: >> >> steamdeck kernel: ? early_xdbc_parse_parameter+0x32c/0x360 >> >> steamdeck kernel: ? setup_early_printk+0x4f5/0x520 >> >> steamdeck kernel: ? do_early_param+0x44/0x70 >> >> steamdeck kernel: ? parse_args+0x233/0x420 >> >> steamdeck kernel: ? __pfx_do_early_param+0x10/0x10 >> >> steamdeck kernel: ? parse_early_options+0x29/0x30 >> >> steamdeck kernel: ? __pfx_do_early_param+0x10/0x10 >> >> steamdeck kernel: ? parse_early_param+0x64/0xc0 >> >> steamdeck kernel: ? setup_arch+0x542/0xbc0 >> >> steamdeck kernel: ? _printk+0x6b/0x90 >> >> steamdeck kernel: ? start_kernel+0x66/0x9a0 >> >> steamdeck kernel: ? x86_64_start_reservations+0x24/0x30 >> >> steamdeck kernel: ? x86_64_start_kernel+0xcc/0xd0 >> >> steamdeck kernel: ? common_startup_64+0x13e/0x141 >> >> steamdeck kernel: >> >> steamdeck kernel: ---[ end trace 0000000000000000 ]--- >> >> >> >> Signed-off-by: Umang Jain >> >> --- >> >> drivers/usb/early/xhci-dbc.c | 8 ++++++++ >> >> 1 file changed, 8 insertions(+) >> >> >> >> diff --git a/drivers/usb/early/xhci-dbc.c b/drivers/usb/early/xhci-dbc.c >> >> index 41118bba9197..699a9ac6d6c3 100644 >> >> --- a/drivers/usb/early/xhci-dbc.c >> >> +++ b/drivers/usb/early/xhci-dbc.c >> >> @@ -76,6 +76,14 @@ static void __iomem * __init xdbc_map_pci_mmio(u32 bus, u32 dev, u32 func) >> >> >> >> sz64 = 1ULL << __ffs64(sz64); >> >> >> >> + /* >> >> + * Check that size does not exceed fixed boot-time mappings >> >> + * dictated by NR_FIX_BTMAPS. early_ioremap() will WARN_ON() >> >> + * and not map memory in those cases. >> >> + */ >> >> + if (sz64 > (NR_FIX_BTMAPS << PAGE_SHIFT)) >> >> + sz64 = NR_FIX_BTMAPS << PAGE_SHIFT; >> > >> > You are bounding the size here, but does this mean that the hardware >> > itself is just broken and should be fixed up to properly report the >> > correct size? Does this hardware actually have a debug controller? >> >> Hmm, to answer your first question as far as I have read, the size is >> inferred from PCI config with base address. My understanding here is >> that >> for early xhci debugging - the page mappings are fixed, so we need to >> bound the size for early_ioremap(). > > So the device is providing the wrong size here? Why is this an issue > only for this hardware and not other hardware? > >> The second answer is, yes the hardware has debug controller. We can >> configure it after boot >> and it works with USB3.1 Superspeed cable with host: >> >> (on target) >> (A+)(root@steamdeck ~)# echo enable > >> /sys/devices/pci0000:00/0000:00:08.1/0000:04:00.3/dbc >> (A+)(root@steamdeck ~)# dmesg | grep DbC >> [ 366.276124] xhci_hcd 0000:04:00.3: DbC connected >> [ 366.637223] xhci_hcd 0000:04:00.3: DbC configured >> >> (on host) >> [114288.650481] usb 4-2: new SuperSpeed USB device number 55 using >> xhci_hcd >> [114288.662907] usb 4-2: New USB device found, idVendor=1d6b, >> idProduct=0010, bcdDevice= 0.10 >> [114288.662935] usb 4-2: New USB device strings: Mfr=1, Product=2, >> SerialNumber=3 >> [114288.662945] usb 4-2: Product: Linux USB Debug Target >> [114288.662953] usb 4-2: Manufacturer: Linux Foundation >> [114288.662960] usb 4-2: SerialNumber: 0001 >> [114288.666320] usb_debug 4-2:1.0: xhci_dbc converter detected >> [114288.666474] usb 4-2: xhci_dbc converter now attached to ttyUSB0 >> >> >> > >> > And what changed to cause this to start complaining? Does it fix a >> > specific commit? This hardware has been around for a long time, did we >> > mess something up in the kernel for it recently? >> >> This fix/patch is only for early xdbc. As mentioned above, it can be >> used/configured after boot. >> So yes, the hardware has been around but I don't think that early xdbc >> capability was investigated at any point in time. I don't see recents >> commits early xhci as well so maybe it was hidden all this time. > > Ok, but it is good to figure out what is "wrong" here that this hardware > is causing this warning to happen, yet other hardware does not. Either > the kernel has always been wrong (totally a possibility), or this > hardware is reporting invalid ranges. Figuring out which is true would > be good to figure out here. Oh yes definitely. I, although don't have any order hardware so I will look around. I haven't investigated the ranges yet, so I will investigate that too. My logic initially was that it's the "early boot" that is forcing a pages/size capping so we need to fit there. >From __early_ioremap() in mm/early_ioremap.c ... /* * Mappings have to fit in the FIX_BTMAP area. */ nrpages = size >> PAGE_SHIFT; if (WARN_ON(nrpages > NR_FIX_BTMAPS)) return NULL; ... > > thanks, > > greg k-h