Re: [PATCH 2/2] ARM: Allow either FLATMEM or SPARSEMEM on the multiplatform build

From: Mike Rapoport <rppt@linux.ibm.com>
To: Florian Fainelli <f.fainelli@gmail.com>
Cc: Doug Berger <opendmb@gmail.com>, Arnd Bergmann <arnd@arndb.de>,
	sboyd@kernel.org, Kevin Cernekee <cernekee@gmail.com>,
	rmk+kernel@armlinux.org.uk, Gregory Fong <gregory.0xf0@gmail.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 2/2] ARM: Allow either FLATMEM or SPARSEMEM on the multiplatform build
Date: Mon, 18 May 2020 22:45:33 +0300	[thread overview]
Message-ID: <20200518194533.GD1059226@linux.ibm.com> (raw)
In-Reply-To: <a7c86780-d65c-ab7b-ec3c-4029257cee7a@gmail.com>

On Mon, May 18, 2020 at 08:58:36AM -0700, Florian Fainelli wrote:
> 
> 
> On 5/7/2020 1:11 PM, Florian Fainelli wrote:
> > 
> > 
> > On 5/7/2020 12:27 AM, Mike Rapoport wrote:
> >> On Wed, May 06, 2020 at 04:50:09PM -0700, Florian Fainelli wrote:
> >>> From: Gregory Fong <gregory.0xf0@gmail.com>
> >>>
> >>> ARMv7 chips with LPAE can often benefit from SPARSEMEM, as portions of
> >>> system memory can be located deep in the 36-bit address space.  Allow
> >>> FLATMEM or SPARSEMEM to be selectable at compile time; FLATMEM remains
> >>> the default.
> >>>
> >>> This is based on Kevin's "[PATCH 3/3] ARM: Allow either FLATMEM or
> >>> SPARSEMEM on the multi-v7 build" from [1] and shamelessly rips off his
> >>> commit message text above.  As Arnd pointed out at [2] there doesn't
> >>> seem to be any reason to tie this specifically to ARMv7, so this has
> >>> been changed to apply to all multiplatform kernels.
> >>>
> >>> [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2014-September/286837.html
> >>> [2] http://lists.infradead.org/pipermail/linux-arm-kernel/2014-October/298950.html
> >>>
> >>> Cc: Kevin Cernekee <cernekee@gmail.com>
> >>> Tested-by: Stephen Boyd <sboyd@codeaurora.org>
> >>> Signed-off-by: Gregory Fong <gregory.0xf0@gmail.com>
> >>> Signed-off-by: Doug Berger <opendmb@gmail.com>
> >>> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> >>> ---
> >>>  arch/arm/Kconfig | 5 +++++
> >>>  1 file changed, 5 insertions(+)
> >>>
> >>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> >>> index 5986277296c3..7bb5264a9c3a 100644
> >>> --- a/arch/arm/Kconfig
> >>> +++ b/arch/arm/Kconfig
> >>> @@ -312,6 +312,8 @@ choice
> >>>  config ARCH_MULTIPLATFORM
> >>>  	bool "Allow multiple platforms to be selected"
> >>>  	depends on MMU
> >>> +	select ARCH_FLATMEM_ENABLE
> >>> +	select ARCH_SPARSEMEM_ENABLE
> >>
> >> The logic in mm/Kconfig is quite convoluted, so selecting
> >> ARCH_SPARSEMEM_ENABLE will automatically make SPARSEMEM the only option.
> >>
> >> On top of this you would need to enable ARCH_SELECT_MEMORY_MODEL, e.g.
> >> something like:
> > 
> > Yes indeed, thanks that does allow me to select between flatmem and
> > sparsemem from menuconfig correctly now.
> 
> Mike, do you want to make a formal submission to Russell's patch
> tracker? If so, feel free to add:

I actually hoped to hear from people what do they think about switching
over to SPARSEMEM for the multiplatform builds. I think at least v7 CPUs
it would make sense.

Russel, Arnd, can you comment please?

> Tested-by: Florian Fainelli <f.fainelli@gmail.com>
> 
> Thanks!
> --
> Florian

-- 
Sincerely yours,
Mike.

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