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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 11944C433EF for ; Tue, 30 Nov 2021 13:19:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231351AbhK3NXA (ORCPT ); Tue, 30 Nov 2021 08:23:00 -0500 Received: from frasgout.his.huawei.com ([185.176.79.56]:4182 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230253AbhK3NW7 (ORCPT ); Tue, 30 Nov 2021 08:22:59 -0500 Received: from fraeml735-chm.china.huawei.com (unknown [172.18.147.201]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4J3N7r5BHkz67Mdm; Tue, 30 Nov 2021 21:18:16 +0800 (CST) Received: from lhreml710-chm.china.huawei.com (10.201.108.61) by fraeml735-chm.china.huawei.com (10.206.15.216) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.20; Tue, 30 Nov 2021 14:19:38 +0100 Received: from localhost (10.202.226.41) by lhreml710-chm.china.huawei.com (10.201.108.61) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.20; Tue, 30 Nov 2021 13:19:38 +0000 Date: Tue, 30 Nov 2021 13:19:36 +0000 From: Jonathan Cameron To: Ben Widawsky CC: , Alison Schofield , Dan Williams , "Ira Weiny" , Vishal Verma Subject: Re: [PATCH 4/9] cxl/pci: Implement Interface Ready Timeout Message-ID: <20211130131936.000039ab@Huawei.com> In-Reply-To: <20211129214721.1668325-5-ben.widawsky@intel.com> References: <20211129214721.1668325-1-ben.widawsky@intel.com> <20211129214721.1668325-5-ben.widawsky@intel.com> Organization: Huawei Technologies Research and Development (UK) Ltd. X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.29; i686-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.226.41] X-ClientProxiedBy: lhreml733-chm.china.huawei.com (10.201.108.84) To lhreml710-chm.china.huawei.com (10.201.108.61) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-cxl@vger.kernel.org On Mon, 29 Nov 2021 13:47:16 -0800 Ben Widawsky wrote: > The original driver implementation used the doorbell timeout for the > Mailbox Interface Ready bit to piggy back off of, since the latter > doesn't have a defined timeout. This functionality, introduced in commit > 8adaf747c9f0 ("cxl/mem: Find device capabilities"), can now be improved > since a timeout has been defined with an ECN to the 2.0 spec. > > While devices implemented prior to the ECN could have an arbitrarily > long wait and still be within spec, the max ECN value (256s) is chosen > as the default for all devices. All vendors in the consortium agreed to > this amount and so it is reasonable to assume no devices made will > exceed this amount. Update the description to talk about the 60 seconds choice. I'm fine with 60 seconds, but I can see it being controversial... > > Signed-off-by: Ben Widawsky > > --- > Changes since v1: > - Use 60 seconds for timeout instead of 256 (Dan) > --- > drivers/cxl/pci.c | 33 +++++++++++++++++++++++++++++++++ > 1 file changed, 33 insertions(+) > > diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c > index 6c8d09fb3a17..b28c220d48ea 100644 > --- a/drivers/cxl/pci.c > +++ b/drivers/cxl/pci.c > @@ -2,6 +2,7 @@ > /* Copyright(c) 2020 Intel Corporation. All rights reserved. */ > #include > #include > +#include > #include > #include > #include > @@ -298,6 +299,38 @@ static int cxl_pci_mbox_send(struct cxl_dev_state *cxlds, struct cxl_mbox_cmd *c > static int cxl_pci_setup_mailbox(struct cxl_dev_state *cxlds) > { > const int cap = readl(cxlds->regs.mbox + CXLDEV_MBOX_CAPS_OFFSET); > + unsigned long timeout; > + u64 md_status; > + int rc; > + > + /* > + * CXL 2.0 ECN "Add Mailbox Ready Time" defines a capability field to > + * dictate how long to wait for the mailbox to become ready. The new > + * field allows the device to tell software the amount of time to wait > + * before mailbox ready. This field allows for up to 255 seconds. 255 > + * seconds is unreasonable long, and longer than other default timeouts > + * in the OS. Use the more sane, 60 seconds instead. > + * > + * 100ms is chosen as the specified pause as it is the value used in the > + * CXL Type 3 Memory Device Software Guide. > + */ > + timeout = jiffies + 60 * HZ; > + > + rc = check_device_status(cxlds); > + if (rc) > + return rc; > + > + do { > + md_status = readq(cxlds->regs.memdev + CXLMDEV_STATUS_OFFSET); > + if (md_status & CXLMDEV_MBOX_IF_READY) > + break; > + if (msleep_interruptible(100)) > + break; > + } while (!time_after(jiffies, timeout)); > + > + /* It's assumed that once the interface is ready, it will remain ready. */ > + if (!(md_status & CXLMDEV_MBOX_IF_READY)) > + return -EIO; > > cxlds->mbox_send = cxl_pci_mbox_send; > cxlds->payload_size =