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 AC631C88E75 for ; Tue, 15 Sep 2026 16:34:05 +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=6lrQWW/YEq4ebFQGF0OLKk9Iw69XrrnuLi271OSb9HA=; b=cZL/z98fvwuJBJGTBrm9acM/Wj jHpMGqdbkYet+00zwBhhjIsb/la9ZDIzagWdkV7qNQl1tFF7nXm9TAvvDz9IHG/tMLmndrfkXtAMi iuYZ8pi8gJsu1fYEdUpscBmx5aMOQsT24sUiUdcDo0a5iwIDmY8CHDVNXO9rGlihVUwBDlpmbXauh qAkBMN3AUynndxgnDoGJlnna7OJUVfRtHzkEC8RJeDbf7ub9mEEghnJHiI+2KyIGN7rS1CoJGBTHI TaZRZaBtbY9CKskoXTbCdRQU8/ghQ17IpDBRLn5YJvalswxqkUfpVJYbvZJjcZ54tDrwo/1eLPVMZ RhC0qWGA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x6W6W-00000007PoD-2crC; Tue, 15 Sep 2026 16:33:56 +0000 Received: from desiato.infradead.org ([2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x6W6M-00000007PmN-3B4B for linux-arm-kernel@bombadil.infradead.org; Tue, 15 Sep 2026 16:33:46 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Transfer-Encoding:Content-Type :In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date:Message-ID: Sender:Reply-To:Content-ID:Content-Description; bh=6lrQWW/YEq4ebFQGF0OLKk9Iw69XrrnuLi271OSb9HA=; b=AaUJbBdpqXMLt6rCpxZhx0p7Jh tZWBCMYmEKj+PO8RSUGW6UtqRg6ZiWu4swWrcQoX1lgMPvkl2DTejkFgasXyMtgkRL6wmtGgGDF2X Dzio0gorQbzLaAZcRIbR401J/n4hwzs5TZd6DWsLax5o8DQmimg8L9lFDPn1FuA6wcOJ4wKmWZKNt OXQ28VCQ1kQcwrflok4yOf8rJ4c8SDTrH2BAh0BC+udkmJbvY3klFip+4B1LGmOqKIUZVSZxMM/sm vlQpO6/ufGV0Gszd0upnzYgSFMLIctcekPjZ0iNKwQ8t5gMVblsW5ktIQrB1d5tkFev7nKG0s6E9h 8VjbeVqQ==; Received: from foss.arm.com ([217.140.110.172]) by desiato.infradead.org with esmtp (Exim 4.99.2 #2 (Red Hat Linux)) id 1x6W6I-000000071em-3YXo for linux-arm-kernel@lists.infradead.org; Tue, 15 Sep 2026 16:33:45 +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 D36A3153B; Tue, 15 Sep 2026 09:33:36 -0700 (PDT) Received: from [10.2.212.8] (e134344.arm.com [10.2.212.8]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D028F3F882; Tue, 15 Sep 2026 09:33:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1789490020; bh=xx9eB9u6r/WPdeitcGw2Om+PjZvqR8Z+lIOP5XRrVY8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=vqwxgydT5NzhSN2Z0f9rmyeFnEtco07D31rIA9SQlSfdE/XzlJiHZkDflSA7mNkJc Rt7eAFb/2C7+ukOgRoKB0XBmy5vieAWEpflOB33ervcsvf9gWWnmmoGnXFejOYsblI 35ZRlK1YmKTVj3O/JeUwKO91ZaT0TwGXhFYXSGAM= Message-ID: Date: Tue, 15 Sep 2026 17:33:36 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 12/14] arm_mpam: detect and enable MPAM-Fb PCC support To: Andre Przywara , 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 , Ritwick Sharma , Gavin Shan , linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20260911112835.714162-1-andre.przywara@arm.com> <20260911112835.714162-13-andre.przywara@arm.com> Content-Language: en-US From: Ben Horgan In-Reply-To: <20260911112835.714162-13-andre.przywara@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260915_173343_219613_96A19D4C X-CRM114-Status: GOOD ( 36.36 ) 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 Andre, On 11/09/2026 12:28, 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 > Tested-by: Ritwick Sharma # on Arm AGI CPU > Reviewed-by: Jonathan Cameron > Tested-by: Srivathsa L Rao > Reviewed-by: Srivathsa L Rao > Reviewed-by: Gavin Shan > --- > drivers/resctrl/Kconfig | 1 + > drivers/resctrl/mpam_devices.c | 119 +++++++++++++++++++++++++++++++- > drivers/resctrl/mpam_fb.c | 41 +++++++++++ > drivers/resctrl/mpam_internal.h | 2 + > 4 files changed, 161 insertions(+), 2 deletions(-) > > diff --git a/drivers/resctrl/Kconfig b/drivers/resctrl/Kconfig > index 9591d792736e5..3f81638f57be3 100644 > --- a/drivers/resctrl/Kconfig > +++ b/drivers/resctrl/Kconfig > @@ -2,6 +2,7 @@ menuconfig ARM64_MPAM_DRIVER > bool "MPAM driver" > depends on ARM64 && ARM64_MPAM > select ACPI_MPAM if ACPI > + select PCC if ACPI > select MAILBOX > help > Memory System Resource Partitioning and Monitoring (MPAM) driver for > diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c > index 14dc8461e4b8f..150a529458388 100644 > --- a/drivers/resctrl/mpam_devices.c > +++ b/drivers/resctrl/mpam_devices.c > @@ -20,14 +20,19 @@ > #include > #include > #include > +#include > #include > #include > #include > +#include > #include > #include > #include > #include > > +#include > +#include > + > #include "mpam_internal.h" > > /* Values for the T241 errata workaround */ > @@ -50,6 +55,87 @@ 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); > + mutex_destroy(&cur->pcc_chan_lock); > + kfree(cur); > +} > + > +static struct mpam_pcc_chan *mpam_pcc_chan_get(struct device *dev, > + int subspace_id) > +{ > + struct mpam_pcc_chan *cur; > + > + 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.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" in us, from the > + * PCC ACPI table. tx_tout is in ms. > + * Add some margin here to be on the safe side. > + */ > + cur->pcc_cl.tx_tout = DIV_ROUND_UP(cur->pcc_chan->latency * 5, 1000); > + > + mutex_init(&cur->pcc_chan_lock); > + > + 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. > @@ -2285,6 +2371,8 @@ static void mpam_msc_drv_remove(struct platform_device *pdev) > if (!msc) > return; > > + mpam_pcc_chan_put(msc->pcc_chan); > + I think this should be in mpam_msc_destroy() so we don't leak the channel on mpam_disable(). Thanks, Ben > mutex_lock(&mpam_list_lock); > mpam_msc_destroy(msc); > mutex_unlock(&mpam_list_lock); > @@ -2295,7 +2383,7 @@ 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; > @@ -2339,7 +2427,7 @@ 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(dev, "pcc-channel", &pcc_subspace_id)) > msc->iface = MPAM_IFACE_MMIO; > else > msc->iface = MPAM_IFACE_PCC; > @@ -2360,6 +2448,33 @@ 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 mpam_fb_msc_id; > + > + msc->pcc_chan = mpam_pcc_chan_get(dev, pcc_subspace_id); > + if (IS_ERR(msc->pcc_chan)) { > + pr_err("Failed to request MSC PCC channel\n"); > + return ERR_CAST(msc->pcc_chan); > + } > + > + err = mpam_fb_check_shared_buffer_size(msc); > + if (err) { > + mpam_pcc_chan_put(msc->pcc_chan); > + > + return ERR_PTR(err); > + } > + > + err = mpam_fb_check_protocol_version(msc); > + if (err) { > + mpam_pcc_chan_put(msc->pcc_chan); > + > + return ERR_PTR(err); > + } > + > + if (device_property_read_u32(&pdev->dev, "mpam-fb-msc-id", > + &mpam_fb_msc_id)) > + mpam_fb_msc_id = msc->id; > + msc->mpam_fb_msc_id = mpam_fb_msc_id; > } else { > return ERR_PTR(-EINVAL); > } > diff --git a/drivers/resctrl/mpam_fb.c b/drivers/resctrl/mpam_fb.c > index 98212f761de38..8fc1d78a7b5ab 100644 > --- a/drivers/resctrl/mpam_fb.c > +++ b/drivers/resctrl/mpam_fb.c > @@ -20,10 +20,15 @@ > #define MPAM_FB_PROTOCOL_ID 0x1a > > #define MPAM_PROTOCOL_VERSION_CMD 0x0 > +#define MPAM_FB_VERSION_MAJOR_MASK GENMASK_U32(31, 16) > +#define MPAM_FB_VERSION_MINOR_MASK GENMASK_U32(15, 0) > + > #define MPAM_MSC_READ_CMD 0x4 > #define MPAM_MSC_WRITE_CMD 0x5 > > #define MPAM_FB_PROT_HEADER_LEN sizeof(u32) > +/* The longest message is MPAM_MSC_WRITE, with 4 parameters. */ > +#define MPAM_FB_MAX_MSG_SIZE (4 * sizeof(u32)) > > #define MPAM_FB_SUCCESS 0 > #define MPAM_FB_ERR_NOT_SUPPORTED -1 > @@ -209,3 +214,39 @@ int mpam_fb_send_write_request(struct mpam_msc *msc, u16 reg, u32 value) > return mpam_fb_send_request(msc, msc->mpam_fb_msc_id, reg, &value, > MPAM_MSC_WRITE_CMD); > } > + > +/* We only support MPAM-Fb protocol version 1.x */ > +int mpam_fb_check_protocol_version(struct mpam_msc *msc) > +{ > + u32 version; > + int ret; > + > + ret = mpam_fb_send_request(msc, 0, 0, &version, > + MPAM_PROTOCOL_VERSION_CMD); > + if (ret) > + return ret; > + > + if (FIELD_GET(MPAM_FB_VERSION_MAJOR_MASK, version) != 1) { > + pr_err("Incompatible MPAM-Fb protocol version %d.%d\n", > + FIELD_GET(MPAM_FB_VERSION_MAJOR_MASK, version), > + FIELD_GET(MPAM_FB_VERSION_MINOR_MASK, version)); > + > + return -EINVAL; > + } > + > + return 0; > +} > + > +int mpam_fb_check_shared_buffer_size(struct mpam_msc *msc) > +{ > + int min_buffer_size = MPAM_FB_MAX_MSG_SIZE + > + sizeof(struct acpi_pcct_ext_pcc_shared_memory); > + > + if (msc->pcc_chan->pcc_chan->shmem_size < min_buffer_size) { > + pr_err("MPAM-Fb PCC channel size too small.\n"); > + > + return -ENOMEM; > + } > + > + return 0; > +} > diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h > index e5a2804facd2d..314d3b48ca9fd 100644 > --- a/drivers/resctrl/mpam_internal.h > +++ b/drivers/resctrl/mpam_internal.h > @@ -538,6 +538,8 @@ static inline void mpam_resctrl_teardown_class(struct mpam_class *class) { } > /* MPAM-Fb Firmware-backed protocol wrappers */ > int mpam_fb_send_read_request(struct mpam_msc *msc, u16 reg, u32 *result); > int mpam_fb_send_write_request(struct mpam_msc *msc, u16 reg, u32 value); > +int mpam_fb_check_protocol_version(struct mpam_msc *msc); > +int mpam_fb_check_shared_buffer_size(struct mpam_msc *msc); > > /* > * MPAM MSCs have the following register layout. See: