[U-Boot] [PATCH] ARM: mxs: fix VDDD brownout setting

[Marek Vasut <marex@denx.de>]

On Sunday, November 15, 2015 at 10:47:12 PM, Michael Heimpold wrote:
> At the moment, the desired brownout is at 1.0V. However,
> this setting cannot be realized by hardware since we have
> only 3 bits to represent the voltage difference from the
> target value.
> 
> Target value is 1500 mV, brownout target is 1000 mV,
> voltage steps are 25 mV.
> 
> Register content calculation:
>   (1500 [mV] - 1000 [mV]) / 25 [mV] = 20 (decimal) = 0x14
> 
>   Register takes only 3 bits, that is 0x4.
> 
> But 0x4 * 25 [mV] = 100 [mV], that means that actual
> brownout level is 1500 [mV] - 100 [mV] = 1.4 V.
> 
> Minimum possible BO level is
>   1500 [mV] - 0x7 * 25 [mV] = 1315 [mV].
> 
> So lets use this value as desired BO value (which is
> also the same as FSL bootlets use).
> 
> Signed-off-by: Michael Heimpold <mhei@heimpold.de>
> Cc: Marek Vasut <marex@denx.de>
> Cc: Otavio Salvador <otavio@ossystems.com.br>
> Cc: Fabio Estevam <fabio.estevam@freescale.com>

Uh, nice find. How did you find it?

Acked-by: Marek Vasut <marex@denx.de>

Best regards,
Marek Vasut