Hi Marek,
Am Monday 16 November 2015, 12:01:36 schrieben Sie:
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?
I was investigating a boot stall with I2SE's Duckbill devices and since we're about to switch from FSL bootlets to U-Boot, I compared the register settings. Then I stumbled about the comment and wondered whether 1.0V BO level makes sense for 1.5V target voltage...
Best regards, Michael Heimpold
Acked-by: Marek Vasut marex@denx.de
Best regards, Marek Vasut