Re: [PATCH v3 01/13] hw/arm/raspi: Use BCM2708 machine type with pre Device Tree kernels

[Niek Linnenbank <nieklinnenbank@gmail.com>]

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On Sat, Feb 8, 2020 at 5:57 PM Philippe Mathieu-Daudé <f4bug@amsat.org>
wrote:

> 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 1df7d1f9303aef
> "raspi: add raspberry pi 2 machine" and 0xc44 in commit bade58166f4
> "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>


> ---
> v3: Improved MACH_TYPE_BCM2708 comment (Zoltán)
> ---
>  hw/arm/raspi.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/hw/arm/raspi.c b/hw/arm/raspi.c
> index 3996f6c63a..f2ccabc662 100644
> --- a/hw/arm/raspi.c
> +++ b/hw/arm/raspi.c
> @@ -29,8 +29,8 @@
>  #define FIRMWARE_ADDR_3 0x80000 /* Pi 3 loads kernel.img here by default
> */
>  #define SPINTABLE_ADDR  0xd8 /* Pi 3 bootloader spintable */
>
> -/* Table of Linux board IDs for different Pi versions */
> -static const int raspi_boardid[] = {[1] = 0xc42, [2] = 0xc43, [3] =
> 0xc44};
> +/* Registered machine type (matches RPi Foundation bootloader and U-Boot)
> */
> +#define MACH_TYPE_BCM2708   3138
>
>  typedef struct RasPiState {
>      BCM283XState soc;
> @@ -116,7 +116,7 @@ static void setup_boot(MachineState *machine, int
> version, size_t ram_size)
>      static struct arm_boot_info binfo;
>      int r;
>
> -    binfo.board_id = raspi_boardid[version];
> +    binfo.board_id = MACH_TYPE_BCM2708;
>      binfo.ram_size = ram_size;
>      binfo.nb_cpus = machine->smp.cpus;
>
> --
> 2.21.1
>
>

-- 
Niek Linnenbank

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