When booting without device tree, the Linux kernels uses the $R1
register to determine the machine type. The list of values is
registered at [1].
There are two entries for the Raspberry Pi:
- https://www.arm.linux.org.uk/developer/machines/list.php?mid=3138
name: MACH_TYPE_BCM2708
value: 0xc42 (3138)
status: Active, not mainlined
date: 15 Oct 2010
- https://www.arm.linux.org.uk/developer/machines/list.php?mid=4828
name: MACH_TYPE_BCM2835
value: 4828
status: Active, mainlined
date: 6 Dec 2013
QEMU always used the non-mainlined type MACH_TYPE_BCM2708.
The value 0xc43 is registered to 'MX51_GGC' (processor i.MX51), and
0xc44 to 'Western Digital Sharespace NAS' (processor Marvell 88F5182).
The Raspberry Pi foundation bootloader only sets the BCM2708 machine
type, see [2] or [3]:
133 9:
134 mov r0, #0
135 ldr r1, =3138 @ BCM2708 machine id
136 ldr r2, atags @ ATAGS
137 bx r4
U-Boot only uses MACH_TYPE_BCM2708 (see [4]):
25 /*
26 * 2835 is a SKU in a series for which the 2708 is the first or primary SoC,
27 * so 2708 has historically been used rather than a dedicated 2835 ID.
28 *
29 * We don't define a machine type for bcm2709/bcm2836 since the RPi Foundation
30 * chose to use someone else's previously registered machine ID (3139, MX51_GGC)
31 * rather than obtaining a valid ID:-/
32 *
33 * For the bcm2837, hopefully a machine type is not needed, since everything
34 * is DT.
35 */
While the definition MACH_BCM2709 with value 0xc43 was introduced in
a commit described "Add 2709 platform for Raspberry Pi 2" out of the
mainline Linux kernel, it does not seem used, and the platform is
introduced with Device Tree support anyway (see [5] and [6]).
Remove the unused values (0xc43 introduced in commit 1df7d1f930
"raspi: add raspberry pi 2 machine" and 0xc44 in commit bade58166f
"raspi: Raspberry Pi 3 support"), keeping only MACH_TYPE_BCM2708.
[1] https://www.arm.linux.org.uk/developer/machines/
[2] https://github.com/raspberrypi/tools/blob/920c7ed2e/armstubs/armstub7.S#L135
[3] https://github.com/raspberrypi/tools/blob/49719d554/armstubs/armstub7.S#L64
[4] https://gitlab.denx.de/u-boot/u-boot/blob/v2015.04/include/configs/rpi-common.h#L18
[5] https://github.com/raspberrypi/linux/commit/d9fac63adac#diff-6722037d79570df5b392a49e0e006573R526
[6] http://lists.infradead.org/pipermail/linux-rpi-kernel/2015-February/001268.html
Cc: Zoltán Baldaszti <bztemail@gmail.com>
Cc: Pekka Enberg <penberg@iki.fi>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Kshitij Soni <kshitij.soni@broadcom.com>
Cc: Michael Chan <michael.chan@broadcom.com>
Cc: Andrew Baumann <Andrew.Baumann@microsoft.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Niek Linnenbank <nieklinnenbank@gmail.com>
Message-id: 20200208165645.15657-2-f4bug@amsat.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
918c81a53e