From: Florian Fainelli <f.fainelli@gmail.com>
To: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Doug Berger <opendmb@gmail.com>, Arnd Bergmann <arnd@arndb.de>,
sboyd@kernel.org, Kevin Cernekee <cernekee@gmail.com>,
Mike Rapoport <rppt@linux.ibm.com>,
Gregory Fong <gregory.0xf0@gmail.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/2] ARM: Remove redundant ARCH_SPARSEMEM_DEFAULT setting
Date: Thu, 7 May 2020 10:25:16 -0700 [thread overview]
Message-ID: <3e7ee3ba-fae9-0ec3-fe1f-c076fc28aba9@gmail.com> (raw)
In-Reply-To: <20200507103039.GR1551@shell.armlinux.org.uk>
On 5/7/2020 3:30 AM, Russell King - ARM Linux admin wrote:
> On Wed, May 06, 2020 at 04:50:08PM -0700, Florian Fainelli wrote:
>> From: Kevin Cernekee <cernekee@gmail.com>
>>
>> If ARCH_SPARSEMEM_ENABLE=y and ARCH_{FLATMEM,DISCONTIGMEM}_ENABLE=n,
>> then the logic in mm/Kconfig already makes CONFIG_SPARSEMEM the only
>> choice. This is true for all of the existing ARM users of
>> ARCH_SPARSEMEM_ENABLE.
>>
>> Forcing ARCH_SPARSEMEM_DEFAULT=y if ARCH_SPARSEMEM_ENABLE=y prevents
>> us from ever defaulting to FLATMEM, so we should remove this setting.
>
> No explanation why that is desirable.
This was explained in the original submission out of which only the
first patch landed upstream:
https://lkml.org/lkml/2015/6/4/756
>
>> -config ARCH_SPARSEMEM_DEFAULT
>> - def_bool ARCH_SPARSEMEM_ENABLE
>> -
>
> What this basically says is ARCH_SPARSEMEM_ENABLE=ARCH_SPARSEMEM_DEFAULT,
> which is exactly what we want for the non-multiplatform boards that
> select ARCH_SPARSEMEM_ENABLE - we _want_ them to default to sparsemem
> because that is what the platform requires.
>
> For example, with RiscPC, which selects ARCH_SPARSEMEM_ENABLE, we have
> four banks of memory at 0x10000000, 0x14000000, 0x18000000 and
> 0x1c000000. These correspond with the two memory slots - the first two
> for the first slot, and the second two for the second slot. Each slot
> has two banks. The size of each memory bank depends on the size of the
> module.
>
> Flatmem is completely unable to work with this setup if all banks are
> populated, and the first bank does not contain enough memory to allocate
> the struct page array. So, sparsemem is the only option there.
>
> Hence, for these platforms, we want sparsemem and only sparsemem, not
> flatmem.
>
> So, this patch which makes it possible to select flatmem is completely
> out of the question for these platforms.
OK.
--
Florian
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next prev parent reply other threads:[~2020-05-07 17:28 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-06 23:50 [PATCH 0/2] Allow either FLATMEM or SPARSEMEM on the multiplatform build Florian Fainelli
2020-05-06 23:50 ` [PATCH 1/2] ARM: Remove redundant ARCH_SPARSEMEM_DEFAULT setting Florian Fainelli
2020-05-07 7:27 ` Mike Rapoport
2020-05-07 10:30 ` Russell King - ARM Linux admin
2020-05-07 17:25 ` Florian Fainelli [this message]
2020-05-07 18:50 ` Russell King - ARM Linux admin
2020-05-07 19:38 ` Florian Fainelli
2020-05-07 20:08 ` [PATCH] arm: use SPARSMEM_STATIC when SPARSEMEM is enabled (Was: [PATCH 1/2] ARM: Remove redundant ARCH_SPARSEMEM_DEFAULT setting) Mike Rapoport
2020-05-08 20:20 ` Florian Fainelli
2020-05-07 20:29 ` [PATCH 1/2] ARM: Remove redundant ARCH_SPARSEMEM_DEFAULT setting Mike Rapoport
2020-05-07 20:47 ` Florian Fainelli
2020-05-08 21:41 ` Mike Rapoport
2020-05-08 21:45 ` Florian Fainelli
2020-05-06 23:50 ` [PATCH 2/2] ARM: Allow either FLATMEM or SPARSEMEM on the multiplatform build Florian Fainelli
2020-05-07 7:27 ` Mike Rapoport
2020-05-07 20:11 ` Florian Fainelli
2020-05-18 15:58 ` Florian Fainelli
2020-05-18 19:45 ` Mike Rapoport
2020-05-19 7:59 ` Arnd Bergmann
2020-05-19 14:43 ` Mike Rapoport
2020-05-19 15:04 ` Russell King - ARM Linux admin
2020-05-19 15:27 ` Mike Rapoport
2020-05-19 15:32 ` Arnd Bergmann
2020-05-19 16:54 ` Russell King - ARM Linux admin
2020-05-19 17:59 ` Mike Rapoport
2020-05-19 20:42 ` Arnd Bergmann
2020-05-21 2:45 ` Florian Fainelli
2020-05-21 7:47 ` Arnd Bergmann
2020-05-07 8:14 ` [PATCH 0/2] " Russell King - ARM Linux admin
2020-05-07 10:09 ` Mike Rapoport
2020-05-21 8:18 [PATCH 0/2] ARM: " Mike Rapoport
2020-05-21 8:18 ` [PATCH 1/2] ARM: Remove redundant ARCH_SPARSEMEM_DEFAULT setting Mike Rapoport
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