From: Arnd Bergmann <arnd@arndb.de>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: Linux ARM <linux-arm-kernel@lists.infradead.org>,
Shawn Guo <shawnguo@kernel.org>,
Fabio Estevam <festevam@gmail.com>,
NXP Linux Team <linux-imx@nxp.com>,
Sascha Hauer <kernel@pengutronix.de>
Subject: Re: [PATCH 09/13] ARM: imx: Remove unused IO_ADDRESS() macros
Date: Tue, 29 Sep 2020 15:21:43 +0200 [thread overview]
Message-ID: <CAK8P3a1wpGTN6C=9eyJzwcwvHSZ5=_HDyJwWrJZx_eYrQ_u2Ng@mail.gmail.com> (raw)
In-Reply-To: <CACRpkdavqDt1do9hAG-eWc0MD-NtyHroocMbt96sRUc__y6q=A@mail.gmail.com>
On Tue, Sep 29, 2020 at 3:11 PM Linus Walleij <linus.walleij@linaro.org> wrote:
> On Thu, Sep 17, 2020 at 9:16 AM Arnd Bergmann <arnd@arndb.de> wrote:
>
> > If all of the devices in here are now also mapped using of_iomap() or
> > ioremap(), then the iotables are not strictly needed any more, but most
> > of them are 1MB section sized, which helps slightly reduce TLB usage
> > compared to non-section ioremap() mappings, so we might want to
> > keep them anyway, possibly with the constants moved from the header
> > into the mm-imx??.c files.
> >
> > Adding Linus to Cc for further thoughts, as he was looking at the early
> > io mappings recently.
>
> There is early fixmap which I think should replace the iotables
> completely if we can, since it is generic kernel code. I was meaning
> to look into this "at some point".
>
> The early fixmap seems to be page (0x1000) based so the iotables
> might be more efficient if using 1MB sections but I doubt that it is
> worth it.
As far as I can tell, the 1MB section maps are the only reason
this exists, as all of them are actually ioremap()ed later on before
use.
I don't know if it makes a difference to real-world performance.
Note that there are only 64 TLB entries on ARM926, or 128 on
ARM1136, so avoiding the lookup/eviction at least theoretically
should be measurably faster.
Arnd
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next prev parent reply other threads:[~2020-09-29 13:23 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-16 20:55 [PATCH 00/13] ARM: imx: Further cleanups due to dt-only conversion Fabio Estevam
2020-09-16 20:55 ` [PATCH 01/13] ARM: dts: imx27: Fix the register range for CCM Fabio Estevam
2020-09-16 20:55 ` [PATCH 02/13] ARM: dts: imx27: Add the SYSCTRL description Fabio Estevam
2020-09-16 20:55 ` [PATCH 03/13] ARM: imx27: Retrieve the SYSCTRL base address from devicetree Fabio Estevam
2020-09-16 21:30 ` Arnd Bergmann
2020-09-16 21:36 ` Fabio Estevam
2020-09-16 20:55 ` [PATCH 04/13] ARM: imx27: Retrieve the CCM " Fabio Estevam
2020-09-16 20:55 ` [PATCH 05/13] ARM: imx31: Retrieve the IIM " Fabio Estevam
2020-09-16 20:55 ` [PATCH 06/13] ARM: imx3: Retrieve the CCM " Fabio Estevam
2020-09-16 20:55 ` [PATCH 07/13] ARM: imx3: Retrieve the AVIC " Fabio Estevam
2020-09-16 20:55 ` [PATCH 08/13] ARM: imx35: Retrieve the IIM " Fabio Estevam
2020-09-16 20:55 ` [PATCH 09/13] ARM: imx: Remove unused IO_ADDRESS() macros Fabio Estevam
2020-09-16 21:34 ` Arnd Bergmann
2020-09-16 21:56 ` Fabio Estevam
2020-09-17 7:16 ` Arnd Bergmann
2020-09-17 10:17 ` Fabio Estevam
2020-09-29 13:11 ` Linus Walleij
2020-09-29 13:21 ` Arnd Bergmann [this message]
2020-09-30 9:34 ` Linus Walleij
2020-09-16 20:55 ` [PATCH 10/13] clk: imx: imx27: Remove mx27_clocks_init() Fabio Estevam
2020-09-16 20:55 ` [PATCH 11/13] clk: imx: imx31: Remove mx31_clocks_init() Fabio Estevam
2020-09-16 20:55 ` [PATCH 12/13] clk: imx: imx35: Remove mx35_clocks_init() Fabio Estevam
2020-09-16 20:55 ` [PATCH 13/13] clk: imx: imx21: Remove clock driver Fabio Estevam
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