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 43548CA5FDD for ; Fri, 2 Oct 2026 15:43:09 +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=6gmpRROWAmgc41T2fhwhnBK3pKrYTzgeeA65AXp4T2U=; b=x7/tu3lDmFdk1z5a5AqxT6mHeX /pYzfQMi0G85YtCwDlQ0Pd4yioqlB2zQJpkLRDFMULGcvWHySfUeFoKa5tfoPoJW9ccUrIUQ5LhFp k3H8kEeqd2KdH8O+ERhvwmGJXeN6dBfMRMPBFA0UGhRoDnkMBc7GoNU3x1EG/gHROhh+xGy7fc3Ko RhwVXnO48pzRExv0F8iwPuiGPfvMEIMVTkXS5DKRfT/F8KE3J4ksbGamzBuU1I8H2OEe/d1D8d1Cu wsw760XQsDtEAQOG7HjOILRA2ffH2ewL1RPadwQqxiXupYS3XItR9pwlTCSBTRU81JcrYAXH41Mz1 5rOfUQeA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xCfPb-0000000By56-0nju; Fri, 02 Oct 2026 15:43:03 +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 1xCfPX-0000000By4J-3Vjt for linux-arm-kernel@lists.infradead.org; Fri, 02 Oct 2026 15:43:01 +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 E02B4143D; Fri, 2 Oct 2026 08:42:54 -0700 (PDT) Received: from [10.211.55.3] (unknown [10.57.85.160]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E47D53F85F; Fri, 2 Oct 2026 08:42:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1790955778; bh=4PLdO4/skYl3QEeQLtcsbR5rTEL+OQYa3stqLZxDFxU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=q5QWC6FuqTAj77ipxz0w2YDhA2CkWarqO7EuYuZwfyMGPGkdSWjjGSVHpAM4AhUzk yBC81GB0ZG2/zGQl/KdQSxSCUdf8ZnhvLAH6zm9KXIcjosFhPKX1fHOsDJogEAzXs/ enLcKGsfZRteWhHmskLcZcGiKVT9YJoBAGZR3RaU= Message-ID: <81ab15fa-98db-499b-9a97-efac6afbcc74@arm.com> Date: Fri, 2 Oct 2026 16:42:53 +0100 MIME-Version: 1.0 User-Agent: Thunderbird Daily Subject: Re: [PATCH v12 13/13] 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--cc, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20261001153439.3295416-1-andre.przywara@arm.com> <20261001153439.3295416-14-andre.przywara@arm.com> Content-Language: en-US From: Ben Horgan In-Reply-To: <20261001153439.3295416-14-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-20261002_084259_970088_403017C9 X-CRM114-Status: GOOD ( 35.00 ) 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 01/10/2026 16:34, 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 Reviewed-by: Ben Horgan Thanks, Ben > --- > 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..f5ff9b1f6c48e 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 08b1e84e3f794..94d6eb6d3a1b2 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. > @@ -2286,6 +2372,8 @@ static void mpam_msc_destroy(struct mpam_msc *msc) > mpam_ris_destroy(ris); > > list_del_rcu(&msc->all_msc_list); > + synchronize_srcu(&mpam_srcu); > + mpam_pcc_chan_put(msc->pcc_chan); > platform_set_drvdata(pdev, NULL); > > add_to_garbage(msc); > @@ -2308,7 +2396,7 @@ 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; > @@ -2352,7 +2440,7 @@ 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; > @@ -2373,6 +2461,33 @@ 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->fb_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 72f45e9582df9..54834052cbde0 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 > @@ -215,3 +220,39 @@ int mpam_fb_send_write_request(struct mpam_msc *msc, u16 reg, u32 value) > return mpam_fb_send_request(msc, msc->fb_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 99057d6abee1e..ee7c3953a9b6c 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: