linux-kernel - Re: [PATCH v8 1/6] gpio: Remove dynamic allocation from populate_parent_alloc

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Date:   Fri, 8 Jul 2022 17:51:39 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Prabhakar <prabhakar.csengg@...il.com>
Cc:     Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Linus Walleij <linus.walleij@...aro.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        devicetree <devicetree@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Biju Das <biju.das.jz@...renesas.com>,
        Daniel Palmer <daniel@...ngy.jp>,
        Romain Perier <romain.perier@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Robert Richter <rric@...nel.org>,
        Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@...hiba.co.jp>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH v8 1/6] gpio: Remove dynamic allocation from populate_parent_alloc_arg()

On Thu, Jul 7, 2022 at 8:24 PM <prabhakar.csengg@...il.com> wrote:
>
> From: Marc Zyngier <maz@...nel.org>
>
> The gpiolib is unique in the way it uses intermediate fwspecs
> when feeding an interrupt specifier to the parent domain, as it
> relies on the populate_parent_alloc_arg() callback to perform
> a dynamic allocation.
>
> This is pretty inefficient (we free the structure almost immediately),
> and the only reason this isn't a stack allocation is that our
> ThunderX friend uses MSIs rather than a FW-constructed structure.
>
> Let's solve it by providing a new type composed of the union
> of a struct irq_fwspec and a msi_info_t, which satisfies both
> requirements. This allows us to use a stack allocation, and we
> can move the handful of users to this new scheme.
>
> Also perform some additional cleanup, such as getting rid of the
> stub versions of the irq_domain_translate_*cell helpers, which
> are never used when CONFIG_IRQ_DOMAIN_HIERARCHY isn't selected.
>
> Tested on a Tegra186.
>
> Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> Cc: Daniel Palmer <daniel@...ngy.jp>
> Cc: Romain Perier <romain.perier@...il.com>
> Cc: Bartosz Golaszewski <brgl@...ev.pl>
> Cc: Thierry Reding <thierry.reding@...il.com>
> Cc: Jonathan Hunter <jonathanh@...dia.com>
> Cc: Robert Richter <rric@...nel.org>
> Cc: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@...hiba.co.jp>
> Cc: Andy Gross <agross@...nel.org>
> Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
> ---

Acked-by: Bartosz Golaszewski <brgl@...ev.pl>