[PATCH 1/2] rpi: Copy properties from firmware dtb to the loaded dtb

[Antoine Mazeas]

Hi Peter,
Thanks for looking at this patch

Le 05/09/2022 à 15:41, Peter Robinson a écrit :
> On Wed, Aug 10, 2022 at 1:58 PM Antoine Mazeas <antoine at karthanis.net> wrote:
>>
>> The RPI firmware adjusts several property values in the dtb it passes
>> to u-boot depending on the board/SoC revision. Inherit some of these
>> when u-boot loads a dtb itself. Specificaly copy:
>>
>> * /model: The firmware provides a more specific string
>> * /memreserve: The firmware defines a reserved range, better keep it
> 
> Is this the CMA range or a different one? If so this makes sense.

This a different range than that of the CMA (which itself is defined at 
/reserved-memory/linux,cma): it's a reserved memory range for the 
VideoCore module on the SoC. In the case of the rpi 400 (and sister 
boards like 4B based on the same chip), the dummy value in the DTB is 
patched by the firmware to a dynamic value set in config.txt; absent 
this config, the default amount is 76 MiBs (see: datasheet 
https://datasheets.raspberrypi.com/bcm2711/bcm2711-peripherals.pdf and 
rpi config reference 
https://www.raspberrypi.com/documentation/computers/config_txt.html#memory-options). 
I can see this happening on my board, where looking at the device tree 
on a running system:

memreserve = <0x3b400000 0x4c00000>; // 0x4c00000 == 76 MiBs

Note the start of the range is also patched in. Given the dynamic nature 
of this setting on at least bcm2711 rpi boards, I think this is worth 
carrying over.

>> * emmc2bus and pcie0 dma-ranges: The C0T revision of the bcm2711 Soc (as
>>    present on rpi 400 and some rpi 4B boards) has different values for
>>    these then the B0T revision. So these need to be adjusted to boot on
>>    these boards
>> * blconfig: The firmware defines the memory area where the blconfig
>>    stored. Copy those over so it can be enabled.
>> * /chosen/kaslr-seed: The firmware generates a kaslr seed, take advantage
>>    of that.
> 
> U-Boot has a rpi4 iproc_rng200 driver for this and provides it via the
> UEFI random seed as well, if you're booting using UEFI that takes
> precedence so providing this might not be useful but also it doesn't
> matter much.
> 
>> Signed-off-by: Sjoerd Simons <sjoerd at collabora.com>
> 
> Reviewed-by: Peter Robinson <pbrobinson at gmail.com>
> Tested-by: Peter Robinson <pbrobinson at gmail.com>
> 
> Tested on RPi400 and it solves the issues with the kernel DT I've seen
> plus some RPi4s although no the rev 1.3+ devices that also have the
> newer SoC rev that's the same in the rpi400
> 
>> ---
>>   board/raspberrypi/rpi/rpi.c | 48 +++++++++++++++++++++++++++++++++++++
>>   1 file changed, 48 insertions(+)
>>
>> diff --git a/board/raspberrypi/rpi/rpi.c b/board/raspberrypi/rpi/rpi.c
>> index 17b8108cc8..28b6f52506 100644
>> --- a/board/raspberrypi/rpi/rpi.c
>> +++ b/board/raspberrypi/rpi/rpi.c
>> @@ -504,10 +504,58 @@ void *board_fdt_blob_setup(int *err)
>>          return (void *)fw_dtb_pointer;
>>   }
>>
>> +int copy_property(void *dst, void *src, char *path, char *property)
>> +{
>> +       int dst_offset, src_offset;
>> +       const fdt32_t *prop;
>> +       int len;
>> +
>> +       src_offset = fdt_path_offset(src, path);
>> +       dst_offset = fdt_path_offset(dst, path);
>> +
>> +       if (src_offset < 0 || dst_offset < 0)
>> +               return -1;
>> +
>> +       prop = fdt_getprop(src, src_offset, property, &len);
>> +       if (!prop)
>> +               return -1;
>> +
>> +       return fdt_setprop(dst, dst_offset, property, prop, len);
>> +}
>> +
>> +/* Copy tweaks from the firmware dtb to the loaded dtb */
>> +void  update_fdt_from_fw(void *fdt, void *fw_fdt)
>> +{
>> +       /* Using dtb from firmware directly; leave it alone */
>> +       if (fdt == fw_fdt)
>> +               return;
>> +
>> +       /* The firmware provides a more precie model; so copy that */
>> +       copy_property(fdt, fw_fdt, "/", "model");
>> +
>> +       /* memory reserve as suggested by the firmware */
>> +       copy_property(fdt, fw_fdt, "/", "memreserve");
>> +
>> +       /* Adjust dma-ranges for the SD card and PCI bus as they can depend on
>> +        * the SoC revision
>> +        */
>> +       copy_property(fdt, fw_fdt, "emmc2bus", "dma-ranges");
>> +       copy_property(fdt, fw_fdt, "pcie0", "dma-ranges");
>> +
>> +       /* Bootloader configuration template exposes as nvmem */
>> +       if (copy_property(fdt, fw_fdt, "blconfig", "reg") == 0)
>> +               copy_property(fdt, fw_fdt, "blconfig", "status");
>> +
>> +       /* kernel address randomisation seed as provided by the firmware */
>> +       copy_property(fdt, fw_fdt, "/chosen", "kaslr-seed");
>> +}
>> +
>>   int ft_board_setup(void *blob, struct bd_info *bd)
>>   {
>>          int node;
>>
>> +       update_fdt_from_fw(blob, (void *)fw_dtb_pointer);
>> +
>>          node = fdt_node_offset_by_compatible(blob, -1, "simple-framebuffer");
>>          if (node < 0)
>>                  fdt_simplefb_add_node(blob);
>> --
>> 2.37.1
>>