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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DC644C53200 for ; Wed, 29 Jul 2026 09:22:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ZHtLfVWn/ovegS/PZ/ROb1caUO4fsxQkBloC3mFL7ok=; b=w0O3K/QZsHHfmim3hqAY+FZhqf mDo8IeRR6h+HjQS4xK3t3lZiSwQUfASrg6dbZamseZ61PzEMjxyjtD58FHelCeortUkX/a/xYpGVW SYUQHEA95r7uMnLWP9+Yow9Td35otfFIHAGkKv2/xUJbtj8L0iAxDH/BWOFWvMZaJ9lIJACA7qYPY KGCHIAuYwd8qhfAnkYO4gnX5z8es3dJKETw0z4cb0buC0e4RogFYfyHavSpTAdRfC+4INFyg31f4e t1/Xdf/Ha7ypuPCV+NUAIhu15OrkVaLuLAHMajF3DD5cg4/85DLAK0NMXpyHjUF0KcuJ4IpzMdD8F gZUs/pIA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wp0UE-00000007LlD-3Bgj; Wed, 29 Jul 2026 09:22:02 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wp0UB-00000007Ljr-3KIw for linux-arm-kernel@lists.infradead.org; Wed, 29 Jul 2026 09:22:02 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 605E7152B; Wed, 29 Jul 2026 02:21:54 -0700 (PDT) Received: from [192.168.178.24] (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D388F3F86F; Wed, 29 Jul 2026 02:21:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1785316918; bh=SdgyO8G5iP25IYD5ge4DY+hn3gXYlzne0rMW3aBjlWg=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=eCGGK4sOSNHV138Kl45IAkTxuUag4MdNpaxeMSX8cJGgM8suLcf+U4qE7sNhEoVtL X6E3HDtjlUyZnI5zn46pybuMNskt/mcAe7tsi0KXlZHHWgBZYpf5tHtFHs3xONLooG +b0BNzwikX5QiKwR8yERLJ/8k9uhRIl+liiHH5v8= Message-ID: Date: Wed, 29 Jul 2026 11:21:53 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 10/10] arm_mpam: detect and enable MPAM-Fb PCC support To: Ben Horgan , Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , Catalin Marinas , Will Deacon , "Rafael J . Wysocki" , Len Brown , James Morse , Reinette Chatre , Fenghua Yu Cc: Jonathan Cameron , Srivathsa L Rao , Ganapatrao Kulkarni , Trilok Soni , Srinivas Ramana , Niyas Sait , Lee Trager , linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20260723155454.1760823-1-andre.przywara@arm.com> <20260723155454.1760823-11-andre.przywara@arm.com> <07375e75-972e-43af-9588-dabb0e81443f@arm.com> Content-Language: en-GB From: Andre Przywara In-Reply-To: <07375e75-972e-43af-9588-dabb0e81443f@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260729_022159_961929_CFE0AAFF X-CRM114-Status: GOOD ( 29.54 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Ben, On 7/29/26 10:56, Ben Horgan wrote: > Hi Andre, > > Just a couple of nits I spotted just now. Ok, thanks, both fixed. Cheers, Andre > > On 7/23/26 16:54, Andre Przywara wrote: >> The Arm MPAM-Fb specification [1] describes a protocol to access MSC >> registers through a firmware interface. This requires a shared memory >> region to hold the message, and a mailbox to trigger the access. >> For ACPI this is wrapped as a PCC channel, described using existing >> ACPI abstractions. >> >> Add code to parse those PCC table descriptions associated with an MSC, >> and store the parsed information in the MSC struct. >> There can be multiple PCC channels, and each channel can serve multiple >> MSCs, so we need to keep track of the channel usage, using a list and >> a refcount. >> This will be used by the MPAM-Fb access wrapper code. >> >> [1] https://developer.arm.com/documentation/den0144/latest >> >> Signed-off-by: Andre Przywara >> --- >> drivers/acpi/arm64/mpam.c | 6 +- >> drivers/resctrl/mpam_devices.c | 127 ++++++++++++++++++++++++++++++++- >> 2 files changed, 129 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/acpi/arm64/mpam.c b/drivers/acpi/arm64/mpam.c >> index 84963a20c3e7..ca9b8754ae5f 100644 >> --- a/drivers/acpi/arm64/mpam.c >> +++ b/drivers/acpi/arm64/mpam.c >> @@ -220,8 +220,8 @@ static struct platform_device * __init acpi_mpam_parse_msc(struct acpi_mpam_msc_ >> struct platform_device *pdev __free(platform_device_put) = >> platform_device_alloc("mpam_msc", tbl_msc->identifier); >> int next_res = 0, next_prop = 0, err; >> - /* pcc, nrdy, affinity and a sentinel */ >> - struct property_entry props[4] = { 0 }; >> + /* pcc, msc-id, nrdy, affinity and a sentinel */ >> + struct property_entry props[5] = { 0 }; >> /* mmio, 2xirq, no sentinel. */ >> struct resource res[3] = { 0 }; >> struct acpi_device *companion; >> @@ -256,6 +256,8 @@ static struct platform_device * __init acpi_mpam_parse_msc(struct acpi_mpam_msc_ >> } else if (iface == MPAM_IFACE_PCC) { >> props[next_prop++] = PROPERTY_ENTRY_U32("pcc-channel", >> tbl_msc->base_address); >> + props[next_prop++] = PROPERTY_ENTRY_U32("msc-id", >> + tbl_msc->identifier); >> } >> >> acpi_mpam_parse_irqs(pdev, tbl_msc, res, &next_res); >> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c >> index fea3161ffbe9..fc4b5f87fbe9 100644 >> --- a/drivers/resctrl/mpam_devices.c >> +++ b/drivers/resctrl/mpam_devices.c >> @@ -19,14 +19,19 @@ >> #include >> #include >> #include >> +#include >> #include >> #include >> #include >> +#include >> #include >> #include >> #include >> #include >> >> +#include >> +#include >> + >> #include "mpam_internal.h" >> >> /* Values for the T241 errata workaround */ >> @@ -49,6 +54,86 @@ static LIST_HEAD(mpam_all_msc); >> >> struct srcu_struct mpam_srcu; >> >> +/* PCC channels might be serving multiple MSCs, so keep a refcounted list. */ >> +static DEFINE_MUTEX(pcc_chan_list_lock); >> +static LIST_HEAD(pcc_chan_list); >> + >> +static void mpam_pcc_chan_release(struct kref *ref) >> +{ >> + struct mpam_pcc_chan *cur = container_of(ref, struct mpam_pcc_chan, >> + refcount); >> + >> + pcc_mbox_free_channel(cur->pcc_chan); >> + list_del(&cur->pcc_chans); >> + kfree(cur); >> +} >> + >> +static struct mpam_pcc_chan *mpam_pcc_chan_get(struct device *dev, >> + int subspace_id) >> +{ >> + struct mpam_pcc_chan *cur; >> + int ret; >> + >> + guard(mutex)(&pcc_chan_list_lock); >> + >> + list_for_each_entry(cur, &pcc_chan_list, pcc_chans) { >> + if (cur->subspace_id == subspace_id) { >> + kref_get(&cur->refcount); >> + >> + return cur; >> + } >> + } >> + >> + cur = kzalloc_obj(*cur); >> + if (!cur) >> + return ERR_PTR(-ENOMEM); >> + >> + cur->pcc_cl.dev = dev; >> + cur->pcc_cl.tx_block = true; >> + >> + cur->pcc_chan = pcc_mbox_request_channel(&cur->pcc_cl, subspace_id); >> + if (IS_ERR(cur->pcc_chan)) { >> + long err = PTR_ERR(cur->pcc_chan); >> + >> + kfree(cur); >> + return ERR_PTR(err); >> + } >> + >> + /* Timeout based on the "nominal latency" from the PCC ACPI table. */ >> + cur->pcc_cl.tx_tout = cur->pcc_chan->latency * 5; >> + >> + ret = devm_mutex_init(dev, &cur->pcc_chan_lock); >> + if (ret) >> + return ERR_PTR(ret); >> + >> + cur->subspace_id = subspace_id; >> + kref_init(&cur->refcount); >> + >> + list_add_tail(&cur->pcc_chans, &pcc_chan_list); >> + >> + return cur; >> +} >> + >> +static int mpam_pcc_chan_put(struct mpam_pcc_chan *pcc_chan) >> +{ >> + struct mpam_pcc_chan *cur, *tmp; >> + >> + if (!pcc_chan) >> + return 0; >> + >> + guard(mutex)(&pcc_chan_list_lock); >> + >> + list_for_each_entry_safe(cur, tmp, &pcc_chan_list, pcc_chans) { >> + if (cur == pcc_chan) { >> + kref_put(&cur->refcount, mpam_pcc_chan_release); >> + >> + return 0; >> + } >> + } >> + >> + return -ENOENT; >> +} >> + >> /* >> * Number of MSCs that have been probed. Once all MSCs have been probed MPAM >> * can be enabled. >> @@ -2201,6 +2286,8 @@ static void mpam_msc_drv_remove(struct platform_device *pdev) >> { >> struct mpam_msc *msc = platform_get_drvdata(pdev); >> >> + mpam_pcc_chan_put(msc->pcc_chan); >> + >> mutex_lock(&mpam_list_lock); >> mpam_msc_destroy(msc); >> mutex_unlock(&mpam_list_lock); >> @@ -2211,7 +2298,7 @@ static void mpam_msc_drv_remove(struct platform_device *pdev) >> static struct mpam_msc *do_mpam_msc_drv_probe(struct platform_device *pdev) >> { >> int err; >> - u32 tmp; >> + u32 pcc_subspace_id; >> struct mpam_msc *msc; >> struct resource *msc_res; >> struct device *dev = &pdev->dev; >> @@ -2259,7 +2346,8 @@ static struct mpam_msc *do_mpam_msc_drv_probe(struct platform_device *pdev) >> if (err) >> return ERR_PTR(err); >> >> - if (device_property_read_u32(&pdev->dev, "pcc-channel", &tmp)) >> + if (device_property_read_u32(&pdev->dev, "pcc-channel", >> + &pcc_subspace_id)) >> msc->iface = MPAM_IFACE_MMIO; >> else >> msc->iface = MPAM_IFACE_PCC; >> @@ -2275,6 +2363,41 @@ static struct mpam_msc *do_mpam_msc_drv_probe(struct platform_device *pdev) >> } >> msc->mapped_hwpage_sz = msc_res->end - msc_res->start; >> msc->mapped_hwpage = io; >> + } else if (msc->iface == MPAM_IFACE_PCC) { >> + u32 msc_id; >> + int ret; >> + >> + if (device_property_read_u32(&pdev->dev, "msc-id", &msc_id)) { > > We have an existing local variable 'dev' we can use here... > >> + pr_err("missing MPAM-Fb MSC identifier\n"); >> + return ERR_PTR(-EINVAL); >> + } >> + msc->mpam_fb_msc_id = msc_id; >> + >> + msc->pcc_chan = mpam_pcc_chan_get(&pdev->dev, pcc_subspace_id); > > and here. > >> + if (IS_ERR(msc->pcc_chan)) { >> + pr_err("Failed to request MSC PCC channel\n"); >> + return ERR_CAST(msc->pcc_chan); >> + } >> + >> + if (msc->pcc_chan->pcc_chan->shmem_size < MPAM_FB_MAX_MSG_SIZE) { >> + pr_err("MPAM-Fb PCC channel size too small.\n"); >> + mpam_pcc_chan_put(msc->pcc_chan); >> + return ERR_PTR(-ENOMEM); >> + } >> + ret = mpam_fb_get_protocol_version(msc); >> + if (ret < 0) { >> + pr_err("Cannot query MPAM-Fb protocol version.\n"); >> + mpam_pcc_chan_put(msc->pcc_chan); >> + >> + /* ret is an MPAM-Fb error code, return a Linux one. */ >> + return ERR_PTR(-EIO); >> + } >> + if ((ret >> 16) != 1) { > > We can use FIELD_GET() to make this check clearer and to populate the error message just below. > >> + pr_err("Incompatible MPAM-Fb protocol version %d.%d\n", >> + ret >> 16, ret & 0xffff); >> + mpam_pcc_chan_put(msc->pcc_chan); >> + return ERR_PTR(-EINVAL); >> + } >> } else { >> return ERR_PTR(-EINVAL); >> } > > Thanks, > > Ben >