From: gregory.clement@free-electrons•com (Gregory CLEMENT)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 7/7] ARM: redo TTBR setup code for LPAE
Date: Thu, 06 Aug 2015 13:14:48 +0200 [thread overview]
Message-ID: <55C341A8.5040504@free-electrons.com> (raw)
In-Reply-To: <20150805160112.GZ7557@n2100.arm.linux.org.uk>
On 05/08/2015 18:01, Russell King - ARM Linux wrote:
> On Wed, Aug 05, 2015 at 05:26:25PM +0200, Gregory CLEMENT wrote:
>> It seems that since the merge of this commit the secondary CPUs on
>> Armada XP failed to come online in Big Endian (my configuration is
>> mvebu_v7_defconfig+CONFIG_CPU_BIG_ENDIAN=y).
>
> That's probably because I don't test big endian at all, never have done,
> and I suspect never will as I've never had systems using BE. So, I regard
> BE as something of a troublesome untestable burden on kernel development.
> (And I've always regarded BE to be an abomination.) In short, I loath
> big endian, which really doesn't bode well for me not constantly cocking
> it up...
>
> My guess is that it all comes down to much of the new code expecting the
> value in r4/r5 to be the least significant 32bits in r4 and the most
> significant 32bits in r5. However, in the secondary code, we load this
> using ldrd, which on BE probably reverses that.
Thanks for the explanation.
>
>> Once I found that this commit introduced the regression I also tested
>> but with LPAE but I had the same result: only the first CPU boot.
>
> Not surprising. I guess BE would need the two registers to mcrr reversing
> if they were a 64-bit value loaded with ldrd.
>
> The simple answer may just be to swap r4/r5 after the ldrd.
I tried this and it fixed the issue.
I will send a patch shortly and if you agree I will submit it to your
patch system.
Thanks,
Gregory
--
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
prev parent reply other threads:[~2015-08-06 11:14 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-06 10:30 [PATCH v2 0/7] Fix Keystone 2 physical address switch Russell King - ARM Linux
2015-05-06 10:30 ` [PATCH 1/7] ARM: keystone2: move platform notifier initialisation into platform init Russell King
2015-05-06 10:30 ` [PATCH 2/7] ARM: keystone2: move update of the phys-to-virt constants into generic code Russell King
2015-05-06 10:30 ` [PATCH 3/7] ARM: keystone2: move address space switch printk " Russell King
2015-05-06 10:30 ` [PATCH 4/7] ARM: keystone2: rename init_meminfo to pv_fixup Russell King
2015-05-06 10:30 ` [PATCH 5/7] ARM: re-implement physical address space switching Russell King
2015-05-11 18:58 ` Nishanth Menon
2015-05-11 19:59 ` Russell King - ARM Linux
2015-05-12 17:22 ` Nishanth Menon
2015-05-06 10:30 ` [PATCH 6/7] ARM: cleanup early_paging_init() calling Russell King
2015-05-06 10:30 ` [PATCH 7/7] ARM: redo TTBR setup code for LPAE Russell King
2015-08-05 15:26 ` Gregory CLEMENT
2015-08-05 16:01 ` Russell King - ARM Linux
2015-08-06 11:14 ` Gregory CLEMENT [this message]
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