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From: Sascha Hauer <s.hauer@pengutronix.de>
To: Rouven Czerwinski <r.czerwinski@pengutronix.de>
Cc: barebox@lists.infradead.org
Subject: Re: [PATCH 2/8] mtd: cfi_flash: allow 0x0 mapping
Date: Tue, 10 Nov 2020 10:15:43 +0100	[thread overview]
Message-ID: <20201110091543.GP29830@pengutronix.de> (raw)
In-Reply-To: <20201110074811.GM29830@pengutronix.de>

On Tue, Nov 10, 2020 at 08:48:11AM +0100, Sascha Hauer wrote:
> On Tue, Nov 10, 2020 at 07:33:53AM +0100, Rouven Czerwinski wrote:
> > On Mon, 2020-11-09 at 14:52 +0100, Lucas Stach wrote:
> > > Am Montag, den 09.11.2020, 14:44 +0100 schrieb Rouven Czerwinski:
> > > > Annotate the different read and write functions with
> > > > zero_page_{access/faulting}. This allows the cfi_flash driver to be used
> > > > on the QEMU virt machine with an enabled MMU.
> > > 
> > > I don't like this zero-page access allow in a driver at all. If you
> > > have some free address space somewhere, you could also solve this issue
> > > by remapping the IO resource to somewhere else in the address space,
> > > deviating from the 1:1 mapping. The Tegra PCIe host driver does this,
> > > if you need some inspiration.
> > 
> > I totally agree, remapping the IO region sounds like a much better
> > choice.
> 
> But where should it be mapped to? Just 4k upwards and hope that the area
> just above the cfi flash isn't occupied by something else?

Ok, here's the plan:

In a board specific initcall map the memory to wherever it's convenient,
modify the address of the CFI flash in the device node and add a big
comment that there's nothing to see here.

Sascha


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  reply	other threads:[~2020-11-10  9:15 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-09 13:44 [PATCH 0/8] QEMU virt machine support via mach-vexpress Rouven Czerwinski
2020-11-09 13:44 ` [PATCH 1/8] ARM: MMU: add zero_page_{access,faulting} Rouven Czerwinski
2020-11-09 13:44 ` [PATCH 2/8] mtd: cfi_flash: allow 0x0 mapping Rouven Czerwinski
2020-11-09 13:52   ` Lucas Stach
2020-11-10  6:33     ` Rouven Czerwinski
2020-11-10  7:48       ` Sascha Hauer
2020-11-10  9:15         ` Sascha Hauer [this message]
2020-11-10  9:36           ` Ahmad Fatoum
2020-11-10  9:43             ` Ahmad Fatoum
2020-11-12 10:06               ` Sascha Hauer
2020-11-12 10:09                 ` Rouven Czerwinski
2020-11-09 13:44 ` [PATCH 3/8] amba: add *_amba_driver helper macros Rouven Czerwinski
2020-11-09 13:44 ` [PATCH 4/8] ARM: vexpress: remove unused KConfig file Rouven Czerwinski
2020-11-09 13:44 ` [PATCH 5/8] ARM: vexpress: convert to board driver Rouven Czerwinski
2020-11-09 13:44 ` [PATCH 6/8] ARM: vexpress: move Options to ARCH_VEXPRESS Rouven Czerwinski
2020-11-09 13:44 ` [PATCH 7/8] ARM: qemu: add support for qemu virt platform Rouven Czerwinski
2020-11-09 13:44 ` [PATCH 8/8] ARM: vexpress: enable VIRT board, MMU and cmds Rouven Czerwinski
2020-11-12 10:30 ` [PATCH 0/8] QEMU virt machine support via mach-vexpress Sascha Hauer

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