From: Mark Rutland <mark.rutland@arm.com>
To: u-boot@lists.denx.de
Subject: [U-Boot] 64Bit device tree compilation
Date: Tue, 24 Mar 2015 10:31:00 +0000 [thread overview]
Message-ID: <20150324103059.GA21642@leverpostej> (raw)
In-Reply-To: <CAEUhbmW2wGxhu3SkyzoOPiUYcqevD46d=_xcfJJdm-fEAin2qw@mail.gmail.com>
Hi,
> Maybe a dumb question, why do we need to have a 64-bit U-Boot for
> arm64? I don't see we ever created 64-bit U-Boot for ppc64.
In ARMv8 it's not possible to change the register width at an exception
level (i.e. you can't change 64->32 or vice-versa), and lower exception
levels cannot be wider (so if your code at EL3 is 32-bit, you cannot run
64-bit code at EL3, EL2, EL1, or EL0).
Therefore you need a purely 64-bit path from EL3 to EL2 or EL1N in order
to boot a 64-bit kernel, so the bootloader needs to be 64-bit.
Mark.
prev parent reply other threads:[~2015-03-24 10:31 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-18 17:17 [U-Boot] 64Bit device tree compilation Hanna Hawa
2015-03-19 13:43 ` Simon Glass
2015-03-19 18:04 ` Thierry Reding
2015-03-24 2:12 ` Bin Meng
2015-03-24 10:31 ` Mark Rutland [this message]
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