linux-kernel - Re: [PATCH 3/9] lib: devres: provide new variants for devm_ioremap

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Date:   Thu, 29 Aug 2019 17:09:35 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Jonathan Corbet <corbet@....net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Alban Bedel <albeu@...e.fr>,
        Linus Walleij <linus.walleij@...aro.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Julia Lawall <Julia.Lawall@...6.fr>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH 3/9] lib: devres: provide new variants for devm_ioremap_resource()

On Thu, Aug 29, 2019 at 4:38 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:

> @@ -710,6 +710,10 @@ extern void devm_free_pages(struct device *dev, unsigned long addr);
>
>  void __iomem *devm_ioremap_resource(struct device *dev,
>                                     const struct resource *res);
> +void __iomem *devm_ioremap_resource_nocache(struct device *dev,
> +                                           const struct resource *res);
> +void __iomem *devm_ioremap_resource_wc(struct device *dev,
> +                                      const struct resource *res);
>
>  void __iomem *devm_of_iomap(struct device *dev,
>                             struct device_node *node, int index,
> diff --git a/lib/devres.c b/lib/devres.c

I think adding devm_ioremap_resource_wc() and
devm_platform_ioremap_resource_wc() makes sense, but I think we're
better off without devm_ioremap_resource_nocache() and
devm_ioremap_resource_cache().

The only architecture that actually has a difference between
ioremap() and ioremap_nocache() seems to be ia64. I would
generally assume that any driver using ioremap_nocache()
that is not ia64 specific should just use ioremap().

The ia64 version of ioremap() tries to guess whether it needs
a cached or uncached mapping, everyone else always
gets uncached these days.

       Arnd