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Message-ID: <e0855325-37be-63ac-a0d5-9cd4cd4d375d@arm.com>
Date: Tue, 3 Oct 2023 17:18:55 +0100
From: Robin Murphy <robin.murphy@....com>
To: Lorenzo Pieralisi <lpieralisi@...nel.org>,
Marc Zyngier <maz@...nel.org>
Cc: linux-kernel@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
Rob Herring <robh+dt@...nel.org>,
Fang Xiang <fangxiang3@...omi.com>
Subject: Re: [PATCH 2/2] irqchip/gic-v3: Enable non-coherent
redistributors/ITSes probing
On 03/10/2023 3:43 pm, Lorenzo Pieralisi wrote:
> On Tue, Sep 05, 2023 at 12:34:58PM +0100, Marc Zyngier wrote:
>
> [...]
>
>>> * Make sure *all* the ITS are reset before we probe any, as
>>> * they may be sharing memory. If any of the ITS fails to
>>> @@ -5396,7 +5405,8 @@ static int __init its_of_probe(struct device_node *node)
>>> continue;
>>> }
>>>
>>> - its_probe_one(&res, &np->fwnode, of_node_to_nid(np));
>>> + its_probe_one(&res, &np->fwnode, of_node_to_nid(np),
>>> + of_property_read_bool(np, "dma-noncoherent"));
>>> }
>>> return 0;
>>> }
>>> @@ -5533,7 +5543,8 @@ static int __init gic_acpi_parse_madt_its(union acpi_subtable_headers *header,
>>> }
>>>
>>> err = its_probe_one(&res, dom_handle,
>>> - acpi_get_its_numa_node(its_entry->translation_id));
>>> + acpi_get_its_numa_node(its_entry->translation_id),
>>> + false);
>>
>> I came up with the following alternative approach, which is as usual
>> completely untested. It is entirely based on the quirk infrastructure,
>> and doesn't touch the ACPI path at all.
>
> Writing the ACPI bits. We can't use the quirks framework for ACPI (we
> don't have "properties" and I don't think we want to attach any to the
> fwnode_handle) that's why I generalized its_probe_one() above with an
> extra param, that would have simplified ACPI parsing:
>
> - we alloc struct its_node in its_probe_one() but at that stage
> ACPI parsing was already done. If we have to parse the MADT(ITS) again
> just to scan for non-coherent we then have to match the MADT entries
> to the *current* struct its_node* we are handling (MADT parsing
> callbacks don't even take a param - we have to resort to global
> variables - definitely doable but it is a bit ugly).
How about a compromise of passing a whole MADT flags field into
its_probe_one() (where its_of_probe() can just pass 0), to pass through
to its_enable_quirks() to then match against an madt_flags field in the
gic_quirk? gic_acpi_init() could then do something similar for the
redistributor quirk, although I guess it would then need to distinguish
GICC and GICR-based quirks cases since the respective flags are in
different formats.
Thanks,
Robin.
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