[U-Boot] [RFT 1/8] exynos: Redo detection of revision when all resources are ready

[Lukasz Majewski <lukma@denx.de>]

Hi Krzysztof,

> Detection of board type is done early - before power setup.  In case
> of Odroid XU3/XU4/HC1 family, the detection is done using ADC which
> is supplied by LDO4/VDD_ADC regulator.  This regulator could be turned
> off (e.g. by kernel before reboot);  If ADC is used early, the
> regulators are not yet available and the detection won't work.
> 
> Try to detect the revision again, once power is brought up.
> 
> This is necessary to fix the detection of Odroid HC1 after reboot, if
> kernel turned off the LDO4 regulator.  Otherwise the board is not
> detected....

But such approach seems not to be the optimal one (as we perform
detection twice - with default LDO4 enabled after power on and after
soft reset).

I would expect to enable the LDO4 regulator in the early code (I2C
would be probably necessary) and then read ADC value properly once.

(I also guess that the "work-by-chance" approach is caused by default
settings of PMIC after power on).

As fair as I remember, TI is able to read the EEPROM via I2C in the
very early u-boot (MLO to be precise) code and then make the decision
regarding the platform.

Maybe it would be possible to do the same with Samsung?

And another thought - if the set_board_type() can be called latter and
it works - why cannot we move it to this latter point and execute
exactly once?

> 
> Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
> ---
>  board/samsung/common/board.c | 19 ++++++++++++++++++-
>  1 file changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/board/samsung/common/board.c
> b/board/samsung/common/board.c index 6fd26a3a9198..1e2dabe68d11 100644
> --- a/board/samsung/common/board.c
> +++ b/board/samsung/common/board.c
> @@ -147,6 +147,11 @@ int board_early_init_f(void)
>  {
>  	int err;
>  #ifdef CONFIG_BOARD_TYPES
> +	/*
> +	 * It is done early so power might not be set up yet.  In
> such case
> +	 * specific revision detection with ADC might not work and
> need to me
> +	 * redone later.
> +	 */
>  	set_board_type();
>  #endif
>  	err = board_uart_init();
> @@ -166,9 +171,21 @@ int board_early_init_f(void)
>  #if defined(CONFIG_POWER) || defined(CONFIG_DM_PMIC)
>  int power_init_board(void)
>  {
> +	int ret;
> +
>  	set_ps_hold_ctrl();
>  
> -	return exynos_power_init();
> +	ret = exynos_power_init();
> +
> +#ifdef CONFIG_BOARD_TYPES
> +	/*
> +	 * Since power is on, redo the board detection (external
> peripherals
> +	 * are on).
> +	 */
> +	set_board_type();
> +#endif
> +
> +	return ret;
>  }
>  #endif
>  




Best regards,

Lukasz Majewski

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