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=-13.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 14B78C433EF for ; Mon, 13 Sep 2021 16:20:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F2A8460EE5 for ; Mon, 13 Sep 2021 16:20:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229732AbhIMQVQ (ORCPT ); Mon, 13 Sep 2021 12:21:16 -0400 Received: from mga01.intel.com ([192.55.52.88]:3398 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229614AbhIMQVP (ORCPT ); Mon, 13 Sep 2021 12:21:15 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10106"; a="244047141" X-IronPort-AV: E=Sophos;i="5.85,290,1624345200"; d="scan'208";a="244047141" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Sep 2021 09:19:59 -0700 X-IronPort-AV: E=Sophos;i="5.85,290,1624345200"; d="scan'208";a="609067345" Received: from dvannith-mobl.amr.corp.intel.com (HELO intel.com) ([10.252.128.229]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Sep 2021 09:19:58 -0700 Date: Mon, 13 Sep 2021 09:19:57 -0700 From: Ben Widawsky To: Jonathan Cameron Cc: linux-cxl@vger.kernel.org, Alison Schofield , Dan Williams , Ira Weiny , Vishal Verma Subject: Re: [PATCH 04/13] cxl: Introduce endpoint decoders Message-ID: <20210913161957.qzaoibfalyoamc5c@intel.com> References: <20210902195017.2516472-1-ben.widawsky@intel.com> <20210902195017.2516472-5-ben.widawsky@intel.com> <20210903153542.00004518@Huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210903153542.00004518@Huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-cxl@vger.kernel.org On 21-09-03 15:35:42, Jonathan Cameron wrote: > On Thu, 2 Sep 2021 12:50:08 -0700 > Ben Widawsky wrote: > > > Endpoints have decoders too. It is useful to share the same > > infrastructure from cxl_core. Endpoints do not have dports (downstream > > targets), only the underlying physical medium. As a result, some special > > casing is needed. > > > > There is no functional change introduced yet as endpoints don't actually > > enumerate decoders yet. > > > > Signed-off-by: Ben Widawsky > > Comments inline... > > > --- > > drivers/cxl/core/bus.c | 29 +++++++++++++++++++++++++---- > > 1 file changed, 25 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/cxl/core/bus.c b/drivers/cxl/core/bus.c > > index 8d5061b0794d..6202ce5a5ac2 100644 > > --- a/drivers/cxl/core/bus.c > > +++ b/drivers/cxl/core/bus.c > > @@ -175,6 +175,12 @@ static const struct attribute_group *cxl_decoder_switch_attribute_groups[] = { > > NULL, > > }; > > > > +static const struct attribute_group *cxl_decoder_endpoint_attribute_groups[] = { > > + &cxl_decoder_base_attribute_group, > > + &cxl_base_attribute_group, > > + NULL, > > +}; > > + > > static void cxl_decoder_release(struct device *dev) > > { > > struct cxl_decoder *cxld = to_cxl_decoder(dev); > > @@ -184,6 +190,12 @@ static void cxl_decoder_release(struct device *dev) > > kfree(cxld); > > } > > > > +static const struct device_type cxl_decoder_endpoint_type = { > > + .name = "cxl_decoder_endpoint", > > + .release = cxl_decoder_release, > > + .groups = cxl_decoder_endpoint_attribute_groups, > > +}; > > + > > static const struct device_type cxl_decoder_switch_type = { > > .name = "cxl_decoder_switch", > > .release = cxl_decoder_release, > > @@ -196,6 +208,11 @@ static const struct device_type cxl_decoder_root_type = { > > .groups = cxl_decoder_root_attribute_groups, > > }; > > > > +static bool is_endpoint_decoder(struct device *dev) > > +{ > > + return dev->type == &cxl_decoder_endpoint_type; > > +} > > + > > bool is_root_decoder(struct device *dev) > > { > > return dev->type == &cxl_decoder_root_type; > > @@ -472,7 +489,7 @@ struct cxl_decoder *cxl_decoder_alloc(struct cxl_port *port, int nr_targets) > > struct device *dev; > > int rc = 0; > > > > - if (nr_targets > CXL_DECODER_MAX_INTERLEAVE || nr_targets < 1) > > Why do we let nr_targets go negative? Could make the parameter unsigned perhaps or > check for that here (even though it makes no sense). Unsigned seems like a good idea to me as well. > > > + if (nr_targets > CXL_DECODER_MAX_INTERLEAVE) > > return ERR_PTR(-EINVAL); > > > > cxld = kzalloc(struct_size(cxld, target, nr_targets), GFP_KERNEL); > > @@ -491,8 +508,11 @@ struct cxl_decoder *cxl_decoder_alloc(struct cxl_port *port, int nr_targets) > > dev->parent = &port->dev; > > dev->bus = &cxl_bus_type; > > > > + /* Endpoints don't have a target list */ > > + if (nr_targets == 0) > > + dev->type = &cxl_decoder_endpoint_type; > > Hmm. Whilst the check seems valid, it's a bit inelegant. > The capability register unhelpfully simply has it defined > as not applicable rather than 0, so I'd be nervous that might > end up here (not checked yet). AFAICT, 0 isn't a valid value in the register at all. Additionally, from the API perspective I don't see much of an issue because nr_targets is the decoded value. So the only entity that should call this with a value of 0 would have to be something which is ignoring the field in the capability register, which would only be an endpoint. > > > /* root ports do not have a cxl_port_type parent */ > > - if (port->dev.parent->type == &cxl_port_type) > > + else if (port->dev.parent->type == &cxl_port_type) > > dev->type = &cxl_decoder_switch_type; > > else > > dev->type = &cxl_decoder_root_type; > > @@ -532,9 +552,11 @@ int cxl_decoder_add(struct device *host, struct cxl_decoder *cxld, > > if (IS_ERR(cxld)) > > return PTR_ERR(cxld); > > > > + dev = &cxld->dev; > > + > > port = to_cxl_port(cxld->dev.parent); > > device_lock(&port->dev); > > - if (list_empty(&port->dports)) { > > + if (is_endpoint_decoder(dev) && list_empty(&port->dports)) { > > rc = -EINVAL; > > goto out_unlock; > > } > > @@ -551,7 +573,6 @@ int cxl_decoder_add(struct device *host, struct cxl_decoder *cxld, > > } > > device_unlock(&port->dev); > > > > - dev = &cxld->dev; > > rc = dev_set_name(dev, "decoder%d.%d", port->id, cxld->id); > > if (rc) > > return rc; >