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 DA760271453 for ; Thu, 7 Aug 2025 18:27:13 +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=1754591235; cv=none; b=LGOfc0a6V6AovT6JVMI+T5CbHXzaTTDGVn32ybPBZWoGRJ8GL0ZFIWW1KF1D8IC4AOT/28v0QIgpYHXtJLdSsw8/XDilli7uqfera7XlFfSKxyuGVqhWnJp+pWx1QpMC3dynHBZdRI/KVYVXdIhbSA1fxtAWG7iMw195j0e3UHU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754591235; c=relaxed/simple; bh=r1tB9aNjTLZ/EWhxtigsydBYEwQj0aorRKIY+uQcnWk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=JDbu2gD4ZtsHdwRaeGqnOKBQpnYThyj8rBwoxMy69oBGIdchlEipOzT6r76aGhMbldlFx8u98N6FfJ+MFn3Ifb6YZPopAXwbF3sL0hj43qFhzNoC6SAgwnAFqmnmrlwslutFmfvMzwV8MD6GCwSECOOYFskrbztv+UvFaDlV0gE= 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; 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 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 D51561756; Thu, 7 Aug 2025 11:27:04 -0700 (PDT) Received: from [10.1.197.43] (eglon.cambridge.arm.com [10.1.197.43]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id ACF743F5A1; Thu, 7 Aug 2025 11:27:04 -0700 (PDT) Message-ID: <48556d36-947b-4e07-aa7e-602bb9fe052d@arm.com> Date: Thu, 7 Aug 2025 19:26:19 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 20/36] arm_mpam: Probe the hardware features resctrl supports To: Ben Horgan , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: Rob Herring , Rohit Mathew , Shanker Donthineni , Zeng Heng , Lecopzer Chen , Carl Worth , shameerali.kolothum.thodi@huawei.com, D Scott Phillips OS , lcherian@marvell.com, bobo.shaobowang@huawei.com, tan.shaopeng@fujitsu.com, baolin.wang@linux.alibaba.com, Jamie Iles , Xin Hao , peternewman@google.com, dfustini@baylibre.com, amitsinght@marvell.com, David Hildenbrand , Rex Nie , Dave Martin , Koba Ko References: <20250711183648.30766-1-james.morse@arm.com> <20250711183648.30766-21-james.morse@arm.com> Content-Language: en-GB From: James Morse In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Ben, On 24/07/2025 16:08, Ben Horgan wrote: > On 7/11/25 19:36, James Morse wrote: >> Expand the probing support with the control and monitor types >> we can use with resctrl. >> diff --git a/drivers/platform/arm64/mpam/mpam_devices.c b/drivers/platform/arm64/mpam/ >> mpam_devices.c >> index 8646fb85ad09..61911831ab39 100644 >> --- a/drivers/platform/arm64/mpam/mpam_devices.c >> +++ b/drivers/platform/arm64/mpam/mpam_devices.c >> @@ -645,6 +659,137 @@ static struct mpam_msc_ris *mpam_get_or_create_ris(struct mpam_msc >> *msc, >>       return found; >>   } >>   +/* >> + * IHI009A.a has this nugget: "If a monitor does not support automatic behaviour >> + * of NRDY, software can use this bit for any purpose" - so hardware might not >> + * implement this - but it isn't RES0. >> + * >> + * Try and see what values stick in this bit. If we can write either value, >> + * its probably not implemented by hardware. >> + */ >> +#define mpam_ris_hw_probe_hw_nrdy(_ris, _mon_reg, _result)            \ >> +do {                                        \ >> +    u32 now;                                \ >> +    u64 mon_sel;                                \ >> +    bool can_set, can_clear;                        \ >> +    struct mpam_msc *_msc = _ris->vmsc->msc;                \ >> +                                        \ >> +    if (WARN_ON_ONCE(!mpam_mon_sel_inner_lock(_msc))) {            \ >> +        _result = false;                        \ >> +        break;                                \ >> +    }                                    \ >> +    mon_sel = FIELD_PREP(MSMON_CFG_MON_SEL_MON_SEL, 0) |            \ >> +          FIELD_PREP(MSMON_CFG_MON_SEL_RIS, _ris->ris_idx);        \ >> +    mpam_write_monsel_reg(_msc, CFG_MON_SEL, mon_sel);            \ >> +                                        \ >> +    mpam_write_monsel_reg(_msc, _mon_reg, MSMON___NRDY);            \ >> +    now = mpam_read_monsel_reg(_msc, _mon_reg);                \ >> +    can_set = now & MSMON___NRDY;                        \ >> +                                        \ >> +    mpam_write_monsel_reg(_msc, _mon_reg, 0);                \ >> +    now = mpam_read_monsel_reg(_msc, _mon_reg);                \ >> +    can_clear = !(now & MSMON___NRDY);                    \ >> +    mpam_mon_sel_inner_unlock(_msc);                    \ >> +                                        \ >> +    _result = (!can_set || !can_clear);                    \ >> +} while (0) > It is a bit surprising that something that looks like a function modifies a boolean passed > by value. > Consider continuing the pattern you have above: > #define mpam_ris_hw_probe_hw_nrdy(_ris, _mon_reg, _result) > _mpam_ris_hw_probe_hw_nrdy(_ris, MSMON##_mon_reg, _result) > > with signature: > void _mpam_ris_hw_probe_hw_nrdy(struct mpam_msc *msc, u16 reg, bool *hw_managed); > > and using the _mpam functions from the new _mpam_ris_hw_probe_hw_nrdy(). With that, it may as well return the result. Done. Thanks, James