Unable to select a different ENV location due env_get_location on zynqmp

[Michal Simek]

Hi,

On 2/14/22 21:10, Ricardo Salveti wrote:
> Hi Michal,
> 
> This is a bit similar to the issue raised on iMX8-based targets a few
> days ago, which is forcing the environment location based on the boot
> mode and not allowing the user to use a different option via other
> CONFIG options.
> 
> Should we really force the env location based on boot mode? Currently
> there is no way to boot out of QSPI and save the environment on
> emmc/fat/ext4, and removing CONFIG_ENV_IS_IN_SPI_FLASH causes the env
> location to be set as ENVL_NOWHERE, which is not ideal, especially
> when other env target locations are available at build time.
> 
> diff --git a/board/xilinx/zynqmp/zynqmp.c b/board/xilinx/zynqmp/zynqmp.c
> index f0be9c022a7..08afb49570a 100644
> --- a/board/xilinx/zynqmp/zynqmp.c
> +++ b/board/xilinx/zynqmp/zynqmp.c
> @@ -969,6 +969,10 @@ enum env_location env_get_location(enum
> env_operation op, int prio)
>          case QSPI_MODE_32BIT:
>                  if (IS_ENABLED(CONFIG_ENV_IS_IN_SPI_FLASH))
>                          return ENVL_SPI_FLASH;
> +               if (IS_ENABLED(CONFIG_ENV_IS_IN_FAT))
> +                       return ENVL_FAT;
> +               if (IS_ENABLED(CONFIG_ENV_IS_IN_EXT4))
> +                       return ENVL_EXT4;
>                  return ENVL_NOWHERE;
>          case JTAG_MODE:
>          default:
> 
> A change like this one would allow other locations to be set, and just
> use the boot mode to assign the priority instead.
> 
> Since I couldn't really find out what is the expected behavior on
> functions defined at soc/board level (env.c sets based on priority,
> depending on what is enabled at build time), I was wondering if we
> shouldn't just drop this function entirely.
> 
> While I agree the board should have a set of defaults, not allowing
> the user to change something like env location via CONFIGs seems wrong
> to me.
> 
> Let me know what you think.

Default location is setup based on how Xilinx sees where that variables should 
be saved for the most cases that's why that function was done like this.
That's why I think that it is very reasonable default setup.
And as is hopefully known we are using pretty generic u-boot which should work 
on all configurations it means default defconfig have all options enabled.

Does it make sense to have an option to change it to any configuration?
Definitely.

How to do it?
DT is for us source of truth that's why I prefer to have DT description which is 
providing all information. It means say where variables should be stored, where 
redundant variables should be stored. IIRC as of today I think they have to be 
on the same device which can be also more flexible. You can specify different 
start/end in qspis, etc.

What has to happen?
Someone has to take a lead and come up with generic universal DT binding to be 
able describe it. Some days ago linaro had similar issue with DT in connection 
to A/B update via GPT partition. And description for it should be pretty much 
the same as is for variables.

Thanks,
Michal