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29 Nov 2018 12:57:40 -0600 Received: from pps.filterd (m0134746.ppops.net [127.0.0.1]) by mx0a-00154901.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id wATIlgt1155006; Thu, 29 Nov 2018 13:57:40 -0500 Received: from esa3.dell-outbound2.iphmx.com (esa3.dell-outbound2.iphmx.com [68.232.154.63]) by mx0a-00154901.pphosted.com with ESMTP id 2p2gf5j6f6-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 29 Nov 2018 13:57:40 -0500 Cc: , , , , , , , , , Received: from ausxipps306.us.dell.com ([143.166.148.156]) by esa3.dell-outbound2.iphmx.com with ESMTP/TLS/DHE-RSA-AES256-SHA256; 30 Nov 2018 00:57:27 +0600 X-LoopCount0: from 10.166.134.89 X-IronPort-AV: E=Sophos;i="5.56,295,1539666000"; d="scan'208";a="244747003" From: To: , Subject: Re: [PATCH] PCI: pciehp: Report degraded links via link bandwidth notification Thread-Topic: [PATCH] PCI: pciehp: Report degraded links via link bandwidth notification Thread-Index: AQHUh3extvl0RTSvTEW+XZDJcp0hUQ== Date: Thu, 29 Nov 2018 18:57:37 +0000 Message-ID: <1828edee07fa483d9600aeb5b9b69456@ausx13mps321.AMER.DELL.COM> References: <20181129000829.14751-1-mr.nuke.me@gmail.com> <20181129173553.GD178809@google.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.178.128.193] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-11-29_11:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=741 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1811290155 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/29/2018 11:36 AM, Bjorn Helgaas wrote:=0A= > On Wed, Nov 28, 2018 at 06:08:24PM -0600, Alexandru Gagniuc wrote:=0A= >> A warning is generated when a PCIe device is probed with a degraded=0A= >> link, but there was no similar mechanism to warn when the link becomes= =0A= >> degraded after probing. The Link Bandwidth Notification provides this=0A= >> mechanism.=0A= >>=0A= >> Use the link bandwidth notification interrupt to detect bandwidth=0A= >> changes, and rescan the bandwidth, looking for the weakest point. This= =0A= >> is the same logic used in probe().=0A= > =0A= > I like the concept of this. What I don't like is the fact that it's=0A= > tied to pciehp, since I don't think the concept of Link Bandwidth=0A= > Notification is related to hotplug. So I think we'll only notice this=0A= > for ports that support hotplug. Maybe it's worth doing it this way=0A= > anyway, even if it could be generalized in the future?=0A= =0A= That makes sense. At first, I thought that BW notification was tied to =0A= hotplug, but our PCIe spec writer disagreed with that assertion. I'm =0A= just not sure where to handle the interrupt otherwise.=0A= =0A= Alex=0A= =0A=