From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.3 required=3.0 tests=DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,HTML_MESSAGE,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 40E5DC3F68F for ; Thu, 13 Feb 2020 17:42:12 +0000 (UTC) Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id AFAD0206ED for ; Thu, 13 Feb 2020 17:42:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="MrPWscfW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AFAD0206ED Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernelnewbies-bounces@kernelnewbies.org Received: from localhost ([::1] helo=shelob.surriel.com) by shelob.surriel.com with esmtp (Exim 4.92.3) (envelope-from ) id 1j2IUO-0003BS-7q; Thu, 13 Feb 2020 12:41:24 -0500 Received: from mail-il1-x130.google.com ([2607:f8b0:4864:20::130]) by shelob.surriel.com with esmtps (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.92.3) (envelope-from ) id 1j2IUM-0003BM-78 for Kernelnewbies@kernelnewbies.org; Thu, 13 Feb 2020 12:41:22 -0500 Received: by mail-il1-x130.google.com with SMTP id b15so5705221iln.3 for ; Thu, 13 Feb 2020 09:41:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:from:date:message-id:subject:to; bh=vbiWmzs0puHckBF+g1LoJPONc++bHz7gsirEmouSYdM=; b=MrPWscfWJ4pURoAyUHbrFeGfWA+xp0BNXsxkglRDHLs6cipg4bMWYcuKu+/1KBiBvX XMfGHNKt5jQHuPmu2+BTK6D7XIyX1Oe3J8RS0LxE7SrHhJ9q6ON5WEzRtPtp24+nHekJ g8RhlDpoe2vJ5BpoqjTRpooQtF8FOwRYaIGeA5bqtrTvld9I2Tn03KDN3i/ZyWVL1QE3 akq0/3ZkHtihzJFzPkk5lP4ZiFfVvaaC5BkrlCOu1trrD+4Lhc5buWejFvjNw+Y3cZAg rTZmLrWglMbsvPXP+Dhub7qtgAPQ2GD74dFgbDJxtpysTGQzhKmWimrGgwbxEG6ild+N hZOA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to; bh=vbiWmzs0puHckBF+g1LoJPONc++bHz7gsirEmouSYdM=; b=CCX2c8/YudxBbMaCp+75uKAu5dwwv8/tfCO1MOZx7Vh/Ks/cw0deCbLZtq5STSBujh skeFAq7Rv/7RaOuW+MNFikuSQnLzbQW/xyZXfrUuqCJ6SFHVQ2S5zVHP7zw1beC8kMmG LqhJ75OkSgkS8HAEkx2EQQ2AWAg4nZYOUz9b9jeJV6PJfQXgkW08tg+Fa3xudJcN71bw 8RUxQq1oPBfX5bDi13IWxsTWpcvzHZngC03xtblMq6H5wOyrzY57i4GoV25XDTEV31Bi 5pukxFiG1UFAi2+M/aJ2OfpcW37lqJlfoqqxinW9ot4mAzkfGwh03h8TUOzSJK2W0vEt YF8Q== X-Gm-Message-State: APjAAAUsZPvbPlyFMWG0IaWIPieKq6TPQteDySX/GnZyJNpEqrBVD1p3 t/N0gMCIaaAVjUMBtCqPm3+z8RHHCNEaP2XXoZLA+Q== X-Google-Smtp-Source: APXvYqxJKFI5Zvn3cbIC/+XzqF0JwBYq8j2qSCg5Kh99PCwJLna6mMtnTAtm5sb76g2uZFpeVcSEULB1W/7QW0u62oY= X-Received: by 2002:a05:6e02:80c:: with SMTP id u12mr17095783ilm.273.1581615669814; Thu, 13 Feb 2020 09:41:09 -0800 (PST) MIME-Version: 1.0 From: Sadanand Warrier Date: Thu, 13 Feb 2020 12:40:59 -0500 Message-ID: Subject: PCIe hotplug To: Kernelnewbies@kernelnewbies.org X-BeenThere: kernelnewbies@kernelnewbies.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Learn about the Linux kernel List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============4407809974734854281==" Errors-To: kernelnewbies-bounces@kernelnewbies.org --===============4407809974734854281== Content-Type: multipart/alternative; boundary="0000000000002bad72059e789865" --0000000000002bad72059e789865 Content-Type: text/plain; charset="UTF-8" Hi I had question about PCIe hotplug. We have hardware that is connected to the host by means of two PCIe switches. i.e. the host sees a PCIe switch connected to one of its buses and on the far side of that switch another PCIe switch which has a PCIe device. It is possible that this device does not train its host facing PCIe links before the server enumerates down its PCI bus and reaches those links. It is also possible the PCIe switch to which the device is attached has not been able to train its own links before server enumeration. Is PCIe hotplug built to work on schemes like this? Let us assume that the hardware has been designed to trasmit a presence signal once the links are trained but this could happen after the server enumeration? Incidentally does the server take advantage of the BIOS/UEFI enumeration? Thanks S --0000000000002bad72059e789865 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hi
=C2=A0 =C2=A0I had=C2=A0 question about PCIe hotplu= g. We have hardware that is connected to the host by means of two PCIe swit= ches. i.e. the host sees a PCIe switch connected to one of its buses and on= the far side of that switch another PCIe switch which has a PCIe device.
=C2=A0 =C2=A0It is possible that this device does not train its ho= st facing PCIe links before the server enumerates down its PCI bus and reac= hes those links. It is also possible the PCIe switch to which the device is= attached has not been able to train its own links before server enumeratio= n.
=C2=A0 Is PCIe hotplug built to work on schemes like this? Let= us assume that the hardware has been designed to trasmit a presence signal= once the links are trained but this could happen=C2=A0after the server enu= meration?
=C2=A0 Incidentally does the server take advantage of t= he BIOS/UEFI enumeration?

Thanks

S
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