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 48A9B39F160; Thu, 30 Apr 2026 09:20:54 +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=1777540856; cv=none; b=QDiYeqgPTnaqQO/bWjFFmwRUmb71WHoduJyLw0RWAB0OpKFBC9gqdqniiU3E6QM6rDfmN5+4lBPUuOpragxHegSTKrtERJ6DjyHsTcQOQXUWURRBkT4ui617ETan8dakOm4UcV/8ukMtDc1VQm1JI5A3p4is+Fq5VRYNfbE6dj0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777540856; c=relaxed/simple; bh=rEuYE3BOp0rZUoRuwFkMAOix88kidy9F1/N55h8chlI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=HQXWUbI+wc6A5dW0CxXOV9ukICdCzceYSf5fnzi9mKjCKz9iFHaqvFyPHHdjAQCG0KYIvTq6AT/0thm29t7vVqZRUfX7Qf54V6+nfJPjPvQCnwXaTbziFffzmPjjTuEMTfm2BnW/6exbS2FDzgWlSB2gvCsDRZHTv2EQIEMidjc= 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=te8cLsXc; 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="te8cLsXc" 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 619F41A9A; Thu, 30 Apr 2026 02:20:41 -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 A06173F7B4; Thu, 30 Apr 2026 02:20:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1777540846; bh=rEuYE3BOp0rZUoRuwFkMAOix88kidy9F1/N55h8chlI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=te8cLsXc/9padMNn1HNRnZmVeeS4irCJgGQmkQUJx4a0oAGiUezq/YFx/bt1hZWB+ POTepneGGzzLeDhIG4eJ7QNqLdMl+Fim4jSGEYfDdhhOMh7KsHE6bFLb79b30UpwCB Eka39O2o43ZkyU0GGXm69bd6Sp8vsAt7UpJDuVVM= Message-ID: Date: Thu, 30 Apr 2026 11:20:42 +0200 Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 5/5] arm_mpam: detect and enable MPAM-Fb PCC support To: Sudeep Holla Cc: Lorenzo Pieralisi , Hanjun Guo , Catalin Marinas , Will Deacon , "Rafael J . Wysocki" , Len Brown , James Morse , Ben Horgan , Reinette Chatre , Fenghua Yu , Jonathan Cameron , linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20260429141339.3171205-1-andre.przywara@arm.com> <20260429141339.3171205-6-andre.przywara@arm.com> <20260430-brave-hoatzin-of-fascination-e7d4ad@sudeepholla> Content-Language: en-US From: Andre Przywara In-Reply-To: <20260430-brave-hoatzin-of-fascination-e7d4ad@sudeepholla> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Sudeep, thanks for having a look! On 4/30/26 10:35, Sudeep Holla wrote: > On Wed, Apr 29, 2026 at 04:13:39PM +0200, 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. >> 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 | 46 +++++++++++++++++++++++++++++++--- >> 2 files changed, 45 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/acpi/arm64/mpam.c b/drivers/acpi/arm64/mpam.c >> index 99c2bdbb3314..edb4d10e8dc3 100644 >> --- a/drivers/acpi/arm64/mpam.c >> +++ b/drivers/acpi/arm64/mpam.c >> @@ -341,6 +341,8 @@ 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 may be looking at the wrong documents, but neither DEN0065 nor DEN0144 carry > any definitions of pcc-channel and msc-id for the device with HID > "“ARMHAA5C". Since "pcc-channel" is already merged, I think I am looking at > wrong documents, please point me to the right one. Please excuse my ignorance, but I was under the assumption that the strings used here are just unique identifiers that need to match the property_get calls in the MPAM code. Is there any requirement to match those property_entry.name fields with the names given in some spec? And those strings are kernel-internal only, right? But for DT would match exactly the property names? Those properties correspond to fields in table 4 in DEN0065, as also described in struct acpi_mpam_msc_node in include/acpi/actbl2.h: - There is "Identifier", that uses distinct IDs for PCC and native MSCs. I named it msc-id, because I'd assume that to be a good name for any (yet to be defined) DT property. - Then there is "Base address", which doubles as the "subspace ID of the PCC channel", when MPAM-Fb is used. As you mentioned, this is already in, and the original spec name would be very misleading, I think. So shall those strings be renamed to match the struct names? Or shall I keep the more readable names as of now, and add comments linking them to the spec/struct? Cheers, Andre