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 5A09AC5516F for ; Fri, 31 Jul 2026 17:04:47 +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: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=1dePP6SoMYOYJBGn1av6tf1YT2EBjHkE2iHv9UFdr8Q=; b=YV7BajIlf3MWbtUvqBiUxWsAOv NdWOi9mnfPLMU2JPjXe4Jgvaxc5TXq8R/eCqQ1RbPDiiHzZUcXjCfwocKrLhdS1bXB0U/4vm/FOzr wMuZDTR3MEGcp9Hmtu/nZo8V7msWCj8VO69LDGTpQWmzFVXtUbbkwztbDXhJLR8+auf05ZDV3x11O RgrLzIWCk/qx3Jmkwq1yKRRyMYpqP0poxZevlkZhjm3Y8Iuk4BuEyEy6dLNGnVX/tP9G2C0gp4Ld2 ZjjvYtont+LMBggT9TTWSOVs0xTEk9Y4qiiNqFVnU2rh3SbUQM2fXbKMVF55YghgcEftgqcpa+k/F OA+eUSGQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wpqex-0000000DCoi-49k1; Fri, 31 Jul 2026 17:04:35 +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 1wpqei-0000000DCfz-3Kkz for linux-arm-kernel@lists.infradead.org; Fri, 31 Jul 2026 17:04:22 +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 276CD15A1; Fri, 31 Jul 2026 10:04:16 -0700 (PDT) Received: from e142021.fritz.box (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A3F0D3F66F; Fri, 31 Jul 2026 10:04:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1785517460; bh=LoUEAE2XLCho+gKtHf451hFKv6eP+Y34GDB8AG2wDnQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mMMGsUZCG/9JmPMfQlXkPRJUs/CtKWAPKfJiPbbWDKiNhqci4oQ+LBgnYPW5iqgKc kELlVC4Xqr04THpmS/3t5QA4oLEKvQsNlGxCtgXrsvav0kKpbuW6YJM1kr1PBtVraA dAx1Xj6Bf62OLgP9lNTWQPHu5KBZBMHIMNWQ45Xs= From: Andre Przywara To: Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , Catalin Marinas , Will Deacon , "Rafael J . Wysocki" , Len Brown , James Morse , Ben Horgan , Reinette Chatre , Fenghua Yu Cc: Jonathan Cameron , Srivathsa L Rao , Ganapatrao Kulkarni , Trilok Soni , Srinivas Ramana , Niyas Sait , Lee Trager , Ritwick Sharma , linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v7 11/11] arm_mpam: detect and enable MPAM-Fb PCC support Date: Fri, 31 Jul 2026 19:03:24 +0200 Message-ID: <20260731170324.2927758-12-andre.przywara@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260731170324.2927758-1-andre.przywara@arm.com> References: <20260731170324.2927758-1-andre.przywara@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260731_100420_925074_25DA6535 X-CRM114-Status: GOOD ( 21.77 ) 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 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 Reviewed-by: Jonathan Cameron --- drivers/resctrl/mpam_devices.c | 113 +++++++++++++++++++++++++++++++- drivers/resctrl/mpam_fb.c | 41 ++++++++++++ drivers/resctrl/mpam_internal.h | 2 + 3 files changed, 154 insertions(+), 2 deletions(-) diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c index b238feb559d4..40b247a89f8e 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 +54,88 @@ 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.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" 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. @@ -2274,6 +2361,8 @@ 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); @@ -2284,7 +2373,7 @@ 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; @@ -2328,7 +2417,7 @@ 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; @@ -2349,6 +2438,26 @@ 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) { + 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); + } } else { return ERR_PTR(-EINVAL); } diff --git a/drivers/resctrl/mpam_fb.c b/drivers/resctrl/mpam_fb.c index 61a91c6cec0a..7a7fb6d067ba 100644 --- a/drivers/resctrl/mpam_fb.c +++ b/drivers/resctrl/mpam_fb.c @@ -37,6 +37,11 @@ #define MPAM_MSC_TOKEN_MASK GENMASK(27, 18) #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_VERSION_MAJOR_MASK GENMASK(31, 16) +#define MPAM_FB_VERSION_MINOR_MASK GENMASK(15, 0) static atomic_t mpam_fb_token = ATOMIC_INIT(0); @@ -207,3 +212,39 @@ int mpam_fb_send_write_request(struct mpam_msc *msc, u16 reg, u32 value) return mpam_fb_send_request(msc->pcc_chan, 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->pcc_chan, 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 %ld.%ld\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 f13a79a84c58..8859189088f3 100644 --- a/drivers/resctrl/mpam_internal.h +++ b/drivers/resctrl/mpam_internal.h @@ -528,6 +528,8 @@ 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: -- 2.43.0