Re: [PATCH v3 1/2] ARM: ITS: implement quirks and add support for Renesas Gen4 ITS

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 15 Jan 2025, Mykyta Poturai wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> 
> There are number of ITS implementations exist which are different from
> the base one which have number of functionalities defined as is
> "IMPLEMENTATION DEFINED", e.g. there may exist differences in cacheability,
> shareability and memory requirements and others. This requires
> appropriate handling of such HW requirements which are implemented as
> ITS quirks: GITS_IIDR (ITS Implementer Identification Register) is used to
> differentiate the ITS implementations and select appropriate set of
> quirks if any.
> 
> As an example of such ITSes add quirk implementation for Renesas Gen4 ITS:
> - add possibility to override default cacheability and shareability
> settings used for ITS memory allocations;
> - change relevant memory allocations to alloc_xenheap_pages which allows
> to specify memory access flags, free_xenheap_pages is used to free;
> - add quirks validation to ensure that all ITSes share the same quirks
> in case of multiple ITSes are present in the system;
> 
> The Gen4 ITS memory requirements are not covered in any errata as of yet,
> but observed behavior suggests that they are indeed required.
> 
> The idea of the quirk implementation is inspired by the Linux kernel ITS
> quirk implementation [1].
> 
> Changelog:
> v2 -> v3:
> - added missing memset;
> v1 -> v2:
> - switched to using alloc_xenheap_pages/free_xenheap_pages for ITS memory
> allocations;
> - updated declaration of its_quirk_flags;
> - added quirks validation to ensure that all ITSes share the same quirks;
> - removed unnecessary vITS changes;
> 
> 
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> Signed-off-by: Mykyta Poturai <mykyta_poturai@xxxxxxxx>
> 
> [1] 
> https://elixir.bootlin.com/linux/v5.16.1/source/drivers/irqchip/irq-gic-v3-its.c

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>