[{"id":3681345,"web_url":"http://patchwork.ozlabs.org/comment/3681345/","msgid":"<252eee19-3a89-42ca-8ccf-60ec93a3724d@kaod.org>","list_archive_url":null,"date":"2026-04-23T09:04:42","subject":"Re: [PATCH v4 14/17] hw/usb/hcd-ehci: Add ctrldssegment-default\n property","submitter":{"id":68548,"url":"http://patchwork.ozlabs.org/api/people/68548/","name":"Cédric Le Goater","email":"clg@kaod.org"},"content":"On 4/23/26 07:18, Jamin Lin wrote:\n> When 64-bit addressing is supported, the Linux EHCI driver programs the\n> segment register to zero. See ehci_run function:\n> https://github.com/torvalds/linux/blob/master/drivers/usb/host/ehci-hcd.c\n> \n> The driver comment also notes that descriptor structures allocated from\n> the DMA pool use segment zero semantics.\n> \n> Descriptor memory is allocated using the DMA API. The platform driver\n> configures a 64-bit DMA mask so memory can be allocated above 4GB.\n> See ehci_platform_probe function:\n> https://github.com/torvalds/linux/blob/master/drivers/usb/host/ehci-platform.c\n> \n> On AST2700 platforms, system DRAM is mapped above 4GB at 0x400000000.\n> As a result, descriptor addresses constructed directly from the guest\n> EHCI registers do not match the actual system address used by the\n> controller when fetching queue heads (QH) and queue element transfer\n> descriptors (qTD).\n> \n> Add a ctrldssegment-default property so platforms can provide a\n> descriptor address offset when constructing descriptor addresses.\n> This allows systems where DRAM resides above 4GB to access EHCI\n> descriptors correctly.\n> \n> The default value is zero, so existing machines are not affected.\n> \n> Signed-off-by: Jamin Lin \n> ---\n> hw/usb/hcd-ehci.h | 5 ++++-\n> hw/usb/hcd-ehci.c | 1 +\n> 2 files changed, 5 insertions(+), 1 deletion(-)\n> \n> diff --git a/hw/usb/hcd-ehci.h b/hw/usb/hcd-ehci.h\n> index 8e6a8cdfb0..3d57e1de5f 100644\n> --- a/hw/usb/hcd-ehci.h\n> +++ b/hw/usb/hcd-ehci.h\n> @@ -264,6 +264,7 @@ struct EHCIState {\n> uint32_t maxframes;\n> bool migrate_fetch_addr_64bit;\n> bool caps_64bit_addr;\n> + uint32_t ctrldssegment_default;\n> \n> /*\n> * EHCI spec version 1.0 Section 2.3\n> @@ -322,7 +323,9 @@ struct EHCIState {\n> DEFINE_PROP_BOOL(\"x-migrate-fetch-addr-64bit\", _state, \\\n> ehci.migrate_fetch_addr_64bit, true), \\\n> DEFINE_PROP_BOOL(\"caps-64bit-addr\", _state, \\\n> - ehci.caps_64bit_addr, false)\n> + ehci.caps_64bit_addr, false), \\\n> + DEFINE_PROP_UINT32(\"ctrldssegment-default\", _state, \\\n> + ehci.ctrldssegment_default, 0)\n> \n> extern const VMStateDescription vmstate_ehci;\n> \n> diff --git a/hw/usb/hcd-ehci.c b/hw/usb/hcd-ehci.c\n> index dfeb8ef70f..e8086f0432 100644\n> --- a/hw/usb/hcd-ehci.c\n> +++ b/hw/usb/hcd-ehci.c\n> @@ -1134,6 +1134,7 @@ static void ehci_opreg_write(void *ptr, hwaddr addr,\n> \" 64-bit addressing capability is disabled\\n\");\n> return;\n> }\n> + val |= s->ctrldssegment_default;\n> break;\n> \n> case ASYNCLISTADDR:\n\nReviewed-by: Cédric Le Goater \n\nThanks,\n\nC.","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=kaod.org header.i=@kaod.org header.a=rsa-sha256\n header.s=ovhmo393970-selector1 header.b=vwGnJmlG;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; helo=lists1p.gnu.org;\n envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n receiver=patchwork.ozlabs.org)","garm.ovh; auth=pass\n (GARM-97G00279735c74-0cf6-43c1-a82d-51e8868adb0d,\n C846149266E0C9F4D826987B86006927C6E58490) smtp.auth=clg@kaod.org"],"Received":["from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17])\n\t(using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits))\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4g1VZW3P9Xz1y2d\n\tfor ; Thu, 23 Apr 2026 19:06:27 +1000 (AEST)","from localhost ([::1] helo=lists1p.gnu.org)\n\tby lists1p.gnu.org with esmtp (Exim 4.90_1)\n\t(envelope-from )\n\tid 1wFpzy-0008FH-OD; Thu, 23 Apr 2026 05:05:28 -0400","from eggs.gnu.org ([2001:470:142:3::10])\n by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)\n (Exim 4.90_1) (envelope-from ) id 1wFpzk-0008Dr-BO\n for qemu-devel@nongnu.org; Thu, 23 Apr 2026 05:05:12 -0400","from 9.mo533.mail-out.ovh.net ([188.165.47.174])\n by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)\n (Exim 4.90_1) (envelope-from ) id 1wFpzZ-0005UK-Rd\n for qemu-devel@nongnu.org; Thu, 23 Apr 2026 05:05:09 -0400","from director5.derp.mail-out.ovh.net\n (director5.derp.mail-out.ovh.net [51.68.94.138])\n by mo533.mail-out.ovh.net (Postfix) with ESMTPS id 4g1VXZ4xjrz5xHC;\n Thu, 23 Apr 2026 09:04:46 +0000 (UTC)","from director5.derp.mail-out.ovh.net\n (director5.derp.mail-out.ovh.net. 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