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Message-ID: <2821782c-67af-432d-8569-4328e6354147@arm.com>
Date: Thu, 30 Jul 2026 12:20:14 +0100
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Subject: Re: [PATCH v5 01/10] arm_mpam: let low level MSC accessors return an
 error
To: Andre Przywara <andre.przywara@arm.com>,
 Lorenzo Pieralisi <lpieralisi@kernel.org>, Hanjun Guo
 <guohanjun@huawei.com>, Sudeep Holla <sudeep.holla@kernel.org>,
 Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>,
 "Rafael J . Wysocki" <rafael@kernel.org>, Len Brown <lenb@kernel.org>,
 James Morse <james.morse@arm.com>,
 Reinette Chatre <reinette.chatre@intel.com>, Fenghua Yu <fenghuay@nvidia.com>
Cc: Jonathan Cameron <jic23@kernel.org>,
 Srivathsa L Rao <srivathsa.rao@oss.qualcomm.com>,
 Ganapatrao Kulkarni <ganapatrao.kulkarni@oss.qualcomm.com>,
 Trilok Soni <tsoni@quicinc.com>, Srinivas Ramana <sramana@qti.qualcomm.com>,
 Niyas Sait <niyas.sait@arm.com>, Lee Trager <lee@trager.us>,
 linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
 linux-kernel@vger.kernel.org
References: <20260729134124.2506269-1-andre.przywara@arm.com>
 <20260729134124.2506269-2-andre.przywara@arm.com>
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From: Ben Horgan <ben.horgan@arm.com>
In-Reply-To: <20260729134124.2506269-2-andre.przywara@arm.com>
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Hi Andre,

On 7/29/26 14:41, Andre Przywara wrote:
> The upcoming MPAM-Fb support does not use MMIO primitives to access an
> MSC, but employs a shared-memory/doorbell based firmware protocol.
> Its complexity means that it must be able to handle errors, whereas we
> always assume an MMIO based MSC access succeeds today.
> 
> Change the __mpam_read_reg() low level accessor function to return the
> requested data through a pointer, and return an error code instead.
> Also change the __mpam_write_reg() accessor function to return an error
> code. At the moment this is always 0, so all error handling paths are
> not exercised at the moment. This will change later when alternative
> MSC access methods like MPAM-Fb are activated.
> 
> Change all direct users of those MSC wrappers to comply with the new
> prototypes, though the errors are not propagated all the way up yet.
> 
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
Reviewed-by: Ben Horgan <ben.horgan@arm.com>

Thanks,

Ben