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Message-ID: <9b630f76-2f9e-fc42-012e-403f4b8c1dee@arm.com>
Date: Mon, 7 Aug 2023 11:03:40 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Will Deacon <will@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org, suzuki.poulose@....com,
Sami Mujawar <sami.mujawar@....com>,
Catalin Marinas <catalin.marinas@....com>,
Mark Rutland <mark.rutland@....com>,
Mike Leach <mike.leach@...aro.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
coresight@...ts.linaro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 1/4] arm_pmu: acpi: Refactor
arm_spe_acpi_register_device()
On 8/4/23 22:09, Will Deacon wrote:
> On Thu, Aug 03, 2023 at 11:43:27AM +0530, Anshuman Khandual wrote:
>>
>>
>> On 8/3/23 11:26, Anshuman Khandual wrote:
>>> + /*
>>> + * Sanity check all the GICC tables for the same interrupt
>>> + * number. For now, only support homogeneous ACPI machines.
>>> + */
>>> + for_each_possible_cpu(cpu) {
>>> + struct acpi_madt_generic_interrupt *gicc;
>>> +
>>> + gicc = acpi_cpu_get_madt_gicc(cpu);
>>> + if (gicc->header.length < len)
>>> + return gsi ? -ENXIO : 0;
>>> +
>>> + this_gsi = parse_gsi(gicc);
>>> + if (!this_gsi)
>>> + return gsi ? -ENXIO : 0;
>>
>> Hello Will,
>>
>> Moved parse_gsi() return code checking to its original place just to
>> make it similar in semantics to existing 'gicc->header.length check'.
>> If 'gsi' is valid i.e atleast a single cpu has been probed, return
>> -ENXIO indicating mismatch, otherwise just return 0.
>
> Wouldn't that still be the case without the check in this hunk? We'd run
> into the homogeneous check and return -ENXIO from there, no?
Although the return code will be the same i.e -ENXIO, but not for the same reason.
this_gsi = parse_gsi(gicc);
if (!this_gsi)
return gsi ? -ENXIO : 0;
This returns 0 when IRQ could not be parsed for the first cpu, but returns -ENXIO
for subsequent cpus. Although return code -ENXIO here still indicates IRQ parsing
to have failed.
} else if (hetid != this_hetid || gsi != this_gsi) {
pr_warn("ACPI: %s: must be homogeneous\n", pdev->name);
return -ENXIO;
}
This returns -ENXIO when there is a IRQ mismatch. But if the above check is not
there, -ENXIO return code here could not be classified into IRQ parse problem or
mismatch without looking into the IRQ value.
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