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=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 D575BC4332F for ; Tue, 14 Sep 2021 21:18:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BBC3E61209 for ; Tue, 14 Sep 2021 21:18:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235326AbhINVTa (ORCPT ); Tue, 14 Sep 2021 17:19:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50128 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235415AbhINVTU (ORCPT ); Tue, 14 Sep 2021 17:19:20 -0400 Received: from mail-pj1-x1030.google.com (mail-pj1-x1030.google.com [IPv6:2607:f8b0:4864:20::1030]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 376A6C0613EE for ; Tue, 14 Sep 2021 14:16:56 -0700 (PDT) Received: by mail-pj1-x1030.google.com with SMTP id g13-20020a17090a3c8d00b00196286963b9so3285226pjc.3 for ; Tue, 14 Sep 2021 14:16:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=jBwDA/ErLIDdu9O9SYU4CQzLY5YQQYi96b4HqA8zEOg=; b=ymVxLSxntmCex2iOuR1Af0qb+ZYKjDkLJJBG4Yix1JHfO241X9mIyo31b5E4GHh0YC XfvRIcTtCXNnZoF/rpfwPGrqsfX6jB/xLb9XkIaxKBFiwFS4q+UVqMnwJbiDcfHIXmZW SKKpvQt5emjPo30cqo/GK0vZBUzxVqldt8t4aIg3hxrOJSxRJBX3qk6SctKldZrNPd04 253gpNeAYSX4cljJBTxPN7IritJ/U6EpB2QBQof/uHQV+F870s3I5VHv6E3E1WgOVH0f AWpJd+uh2hp9dnojf7URe5+BLr2ZpIaNOguw8QMLvg7v5l6YKSeBY8YXtKEOq1jBaqvP UAJQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=jBwDA/ErLIDdu9O9SYU4CQzLY5YQQYi96b4HqA8zEOg=; b=vtYJtizSdTs5Fyx4t/CPYNVahRiqLA/uKzpoJz7+3Qmj/2NFb7RSmLfyvPCYCBq/b8 aVo9jJqAf1+D+IL50FAoKMiLxKQTedgnm05HqhiE2ly+ijznZen9K09ikG7rCuUnXOFO /xrRJclh+Bl3DHGIxLfD7pPkz9h1hE2tnG1lO+cvff37ELVxQjTa6d79no2Zm+j4elz3 ZojXELl0THGnBQ7A3ypYpiiSKoGoDE5sdcUcaA0G2lN/lLlD1E7+6W+d4C3KAW+B+S4U Nr2npck/w35vZQ27lnChtqQKAaRW9xFoNvJjpCMNV9fQdugJ+Tuu3+LHPJ1G7+30Ff66 8ixg== X-Gm-Message-State: AOAM530gP+66GR7oQcqo7NOLyjZEILoMrZyGX5GQOdpsoIJo8wGOoHr/ zUyVpGCgQHvSoU5O6JJkUk0fv6A0wMLgcCS3sOmaJg== X-Google-Smtp-Source: ABdhPJwNbGLX50LIB5DPTVHeZuGS+NGNREa0vxHkxd1RDgJ67moxMPKeJ14C5qLzKpmhyCH3yMdqgG2jmFPPpOM+rhU= X-Received: by 2002:a17:902:cec8:b0:13b:9ce1:b3ef with SMTP id d8-20020a170902cec800b0013b9ce1b3efmr8113297plg.4.1631654215629; Tue, 14 Sep 2021 14:16:55 -0700 (PDT) MIME-Version: 1.0 References: <20210902195017.2516472-1-ben.widawsky@intel.com> <20210902195017.2516472-5-ben.widawsky@intel.com> <20210913161149.ggbd5jmro2davaq5@intel.com> <20210913231921.w2rujefmewgraopi@intel.com> In-Reply-To: <20210913231921.w2rujefmewgraopi@intel.com> From: Dan Williams Date: Tue, 14 Sep 2021 14:16:44 -0700 Message-ID: Subject: Re: [PATCH 04/13] cxl: Introduce endpoint decoders To: Ben Widawsky Cc: linux-cxl@vger.kernel.org, Alison Schofield , Ira Weiny , Jonathan Cameron , Vishal Verma Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-cxl@vger.kernel.org On Mon, Sep 13, 2021 at 4:19 PM Ben Widawsky wrote: > > On 21-09-13 15:07:44, Dan Williams wrote: > > On Mon, Sep 13, 2021 at 9:11 AM Ben Widawsky wrote: > > > > > > On 21-09-10 12:19:24, Dan Williams wrote: > > > > On Thu, Sep 2, 2021 at 12:50 PM 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 > > > > > --- > > > > > 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) > > > > > + 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; > > > > > > > > Do you also plan to introduce the concept of endpoint ports, and if > > > > yes should that come before this patch? That would seem to be more > > > > robust than, for example, allowing a switch port to carry an endpoint > > > > decoder object as this allows. > > > > > > I didn't see a need as of yet to differentiate between endpoint ports and other > > > ports. I don't entirely understand what you mean by "allowing a switch port to > > > carry an endpoint decoder" means. Can you please elaborate? > > > > If endpoint ports were an explicit type then this check could make > > sure that someone did not pass nr_targets set to 0 where the @port > > argument is referring to a switch where the target_list must be > > specified. > > > > Either that, or a comment in kernel-doc for this routine about the > > special meaning of nr_targets == 0 and expected usage. > > Well, since Jonathan also brought up a concern here perhaps I should entertain > other ideas. I suppose future versions of the spec could break things, but as it > stands today the only CXL component that implements decoders that can have a 0 > value for this are endpoint devices (T2 or T3, or LD). I think it's fine to wait > until we have a second reason to make an endpoint port type and update kdocs for > now, but maybe it will also be a natural fit with a proper port driver. "Document only" sounds good to me.