Re: [Qemu-devel] [PATCH v2 2/3] raspi: Raspberry Pi 3 support

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

Hi Pekka and Zoltán,

On Fri, Feb 16, 2018 at 8:04 AM Pekka Enberg <penberg@iki.fi> wrote:
>
> This patch adds Raspberry Pi 3 support to hw/arm/raspi.c. The
> differences to Pi 2 are:
>
>  - Firmware address
>  - Board ID
>  - Board revision
>
> The CPU is different too, but that's going to be configured as part of
> the machine default CPU when we introduce a new machine type.
>
> The patch was written from scratch by me but the logic is similar to
> Zoltán Baldaszti's previous work, which I used as a reference (with
> permission from the author):
>
>   https://github.com/bztsrc/qemu-raspi3
>
> Signed-off-by: Pekka Enberg <penberg@iki.fi>
> ---
>  hw/arm/raspi.c | 31 +++++++++++++++++++++----------
>  1 file changed, 21 insertions(+), 10 deletions(-)
>
> diff --git a/hw/arm/raspi.c b/hw/arm/raspi.c
> index c24a4a1b14..66fe10e376 100644
> --- a/hw/arm/raspi.c
> +++ b/hw/arm/raspi.c
> @@ -5,6 +5,9 @@
>   * Rasperry Pi 2 emulation Copyright (c) 2015, Microsoft
>   * Written by Andrew Baumann
>   *
> + * Raspberry Pi 3 emulation Copyright (c) 2018 Zoltán Baldaszti
> + * Upstream code cleanup (c) 2018 Pekka Enberg
> + *
>   * This code is licensed under the GNU GPLv2 and later.
>   */
>
> @@ -22,10 +25,11 @@
>  #define SMPBOOT_ADDR    0x300 /* this should leave enough space for ATAGS */
>  #define MVBAR_ADDR      0x400 /* secure vectors */
>  #define BOARDSETUP_ADDR (MVBAR_ADDR + 0x20) /* board setup code */
> -#define FIRMWARE_ADDR   0x8000 /* Pi loads kernel.img here by default */
> +#define FIRMWARE_ADDR_2 0x8000 /* Pi 2 loads kernel.img here by default */
> +#define FIRMWARE_ADDR_3 0x80000 /* Pi 3 loads kernel.img here by default */
>
>  /* Table of Linux board IDs for different Pi versions */
> -static const int raspi_boardid[] = {[1] = 0xc42, [2] = 0xc43};
> +static const int raspi_boardid[] = {[1] = 0xc42, [2] = 0xc43, [3] = 0xc44};

Where does the value 0xc44 comes from?

I can only find 0xc42/0xc43 defined:
https://github.com/raspberrypi/linux/blob/rpi-3.18.y/arch/arm/tools/mach-types#L525

0xc43 seems controversial, see
http://lists.infradead.org/pipermail/linux-rpi-kernel/2015-February/001268.html
addition: https://github.com/raspberrypi/linux/commit/d9fac63adac#diff-6722037d79570df5b392a49e0e006573R526

Looking at the firmware source, the r1 register is always set to the
BCM2708 machine id before calling the kernel:
https://github.com/raspberrypi/tools/blob/920c7ed2ee/armstubs/armstub7.S#L133

Thanks,

Phil.