From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id A1B2D21638D; Thu, 9 Jul 2026 09:42:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783590133; cv=none; b=R05LQp7ViIwmKY0omBMVOvzwfAAUzWvTyjwHY7RG1RInoH/HFqR9xUOl6ZGUihAaxi12wlxlYuX/snOba7IoGvNjmydkrdzcZd62jDRa1LnDr7c6CZ7nJ493ZiphBV+eP11MVqWa2X7zwgEpzx5PeTt6JcDJWGNLphD11HWSprM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783590133; c=relaxed/simple; bh=cBftvfYKfjyrhkBoYN/QBxyh1X9llmuITuh/+JJ4C4w=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=qXxfEEuqh1ubyhDGHXzmfz12cgkGghvnYw2tVfF3CoW+2d1GIzHfCmAumHkRavnYrk1BPQFFYjQfXGJVoTfwdSQ55bNVjJL7tNLzGMrqdGsZiQPwteb9EgClakidMlUgYhk/e03K61vZUbmjCZibQ8PSCZf4657mPjd9YMmUWT4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=WiH6vkn6; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="WiH6vkn6" 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 9DF6C357B; Thu, 9 Jul 2026 02:42:06 -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 4E6243FDE2; Thu, 9 Jul 2026 02:42:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1783590130; bh=cBftvfYKfjyrhkBoYN/QBxyh1X9llmuITuh/+JJ4C4w=; h=Date:Subject:From:To:Cc:References:In-Reply-To:From; b=WiH6vkn6b7SXPDUKa1/hnnKeDU9DHSXIplaQy9IF6i2hz3+c58RQvK4xJoM0DzH8V q2E56Y8XKozu7W3HaDr4ra6yOBmnPjIzStuOEBte0ZGXgDX6zJLPmt5FbNtaXaPAMc sAZRfMk0qTjRqvSLd/S8JSnOVk0R2VTm/vAAmhdw= Message-ID: <299507de-b8f0-4d2f-8845-5266ce495eb1@arm.com> Date: Thu, 9 Jul 2026 10:42:06 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Thunderbird Daily Subject: Re: [PATCH v2 15/15] arm_mpam: detect and enable MPAM-Fb PCC support From: Ben Horgan 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 , linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20260702162229.4008659-1-andre.przywara@arm.com> <20260702162229.4008659-16-andre.przywara@arm.com> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Andre, On 7/3/26 12:00, Ben Horgan wrote: > Hi Andre, > > On 7/2/26 17:22, 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 | 2 + >> drivers/resctrl/mpam_devices.c | 113 ++++++++++++++++++++++++++++++++- >> 2 files changed, 113 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/acpi/arm64/mpam.c b/drivers/acpi/arm64/mpam.c >> index 84963a20c3e7..64bc84bb2029 100644 >> --- a/drivers/acpi/arm64/mpam.c >> +++ b/drivers/acpi/arm64/mpam.c >> @@ -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); I expect it's easier if changes in this file are a separate patch Just to help bring this to the attention of the ACPI/arm64 maintainers. Thanks, Ben >> } >> >> 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 4a088e6cd235..35214520bfd4 100644 >> --- a/drivers/resctrl/mpam_devices.c >> +++ b/drivers/resctrl/mpam_devices.c >> @@ -19,6 +19,7 @@ >> #include >> #include >> #include >> +#include >> #include >> #include >> #include >> @@ -27,6 +28,9 @@ >> #include >> #include >> >> +#include >> +#include >> + >> #include "mpam_internal.h" >> #include "mpam_fb.h" >> >> @@ -50,6 +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_rx_callback(struct mbox_client *cl, void *msg) >> +{ >> + /* TODO: wake up tasks blocked on this MSC's PCC channel */ >> +} >> + >> +static struct mpam_pcc_chan *mpam_pcc_chan_get(struct device *dev, >> + int subspace_id) >> +{ >> + struct mpam_pcc_chan *cur; >> + >> + mutex_lock(&pcc_chan_list_lock); >> + >> + list_for_each_entry(cur, &pcc_chan_list, pcc_chans) { >> + if (cur->subspace_id == subspace_id) { >> + cur->refcount++; >> + mutex_unlock(&pcc_chan_list_lock); >> + >> + return cur; >> + } >> + } >> + >> + cur = kzalloc_obj(*cur); >> + if (!cur) { >> + mutex_unlock(&pcc_chan_list_lock); >> + return ERR_PTR(-ENOMEM); >> + } >> + >> + cur->pcc_cl.dev = dev; >> + cur->pcc_cl.rx_callback = mpam_pcc_rx_callback; >> + cur->pcc_cl.tx_block = true; >> + cur->pcc_cl.tx_tout = 1000; /* 1s */ >> + >> + 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); >> + mutex_unlock(&pcc_chan_list_lock); >> + return ERR_PTR(err); >> + } >> + >> + mutex_init(&cur->pcc_chan_lock); >> + cur->subspace_id = subspace_id; >> + cur->refcount = 1; >> + >> + list_add_tail(&cur->pcc_chans, &pcc_chan_list); >> + >> + mutex_unlock(&pcc_chan_list_lock); >> + >> + 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; >> + >> + mutex_lock(&pcc_chan_list_lock); >> + >> + list_for_each_entry_safe(cur, tmp, &pcc_chan_list, pcc_chans) { >> + if (cur == pcc_chan) { >> + if (!--cur->refcount) { >> + pcc_mbox_free_channel(cur->pcc_chan); >> + list_del(&pcc_chan->pcc_chans); >> + kfree(cur); >> + } >> + mutex_unlock(&pcc_chan_list_lock); >> + return 0; >> + } >> + } >> + >> + mutex_unlock(&pcc_chan_list_lock); >> + >> + return -ENOENT; >> +} >> + >> /* >> * Number of MSCs that have been probed. Once all MSCs have been probed MPAM >> * can be enabled. >> @@ -2202,6 +2288,8 @@ 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); >> @@ -2212,7 +2300,7 @@ 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; >> @@ -2257,7 +2345,8 @@ 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; >> @@ -2273,6 +2362,26 @@ 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) { >> + u32 msc_id; >> + >> + if (device_property_read_u32(&pdev->dev, "msc-id", &msc_id)) { >> + 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); >> + if (IS_ERR(msc->pcc_chan)) { >> + pr_err("Failed to request MSC PCC channel\n"); >> + return (void *)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); >> + } > > I think we need a version check here just in case a MPAM-Fb 2.x is released. > > Thanks, > > Ben > >> } else { >> return ERR_PTR(-EINVAL); >> } >