[meta-ti] Is it possible to change the operating voltage at a particular frequency for BBxM

[Luis Alfonso Maeda-Nunez]

Hi,

I am using the BBxM revC1, Ubuntu 12.04 with kernel 3.7.10-x10+.
Does anyone know if it is possible to run the BBxM at a different 
voltage than the one stated?
For example running at lowest frequency (300MHz) the system reports:

|
root at arm:/# cat /sys/class/regulator/regulator.4/name
vdd_mpu_iva

root at arm:/# cat /sys/class/regulator/regulator.4/microvolts
1012500

root at arm:/# cat /sys/class/regulator/regulator.4/max_microvolts
1450000

root at arm:/# cat /sys/class/regulator/regulator.4/min_microvolts
600000

|

Is it possible to change that "1012500" to lets say "1000000" or 
"900000"?*I am testing for reliability so I want to push the voltage as 
low as possible.*

According to the BBxM datasheet page 59 (7.7.5) VDD1 (vdd_mpu_iva) may 
be controlled using the SmartReflex controller (by I2C), configuring the 
output voltage of the TPS65950 between 0.6V and 1.45V in steps of 12.5mV 
(as stated before).

I know it may have to be done at Kernel cross-compiling stage, so 
digging into the kernel source code I found in 
<kernel>/arch/arm/mach-omap2/omap3xxx_data.c

Line:58
|
/* 36xx */

/* VDD1 */

#define OMAP3630_VDD_MPU_OPP50_UV1012500
#define OMAP3630_VDD_MPU_OPP100_UV1200000
#define OMAP3630_VDD_MPU_OPP120_UV1325000
#define OMAP3630_VDD_MPU_OPP1G_UV1375000

struct omap_volt_data omap36xx_vddmpu_volt_data[] = {
VOLT_DATA_DEFINE(OMAP3630_VDD_MPU_OPP50_UV, 
OMAP3630_CONTROL_FUSE_OPP50_VDD1, 0xf4, 0x0c),
VOLT_DATA_DEFINE(OMAP3630_VDD_MPU_OPP100_UV, 
OMAP3630_CONTROL_FUSE_OPP100_VDD1, 0xf9, 0x16),
VOLT_DATA_DEFINE(OMAP3630_VDD_MPU_OPP120_UV, 
OMAP3630_CONTROL_FUSE_OPP120_VDD1, 0xfa, 0x23),
VOLT_DATA_DEFINE(OMAP3630_VDD_MPU_OPP1G_UV, 
OMAP3630_CONTROL_FUSE_OPP1G_VDD1, 0xfa, 0x27),
VOLT_DATA_DEFINE(0, 0, 0, 0),
};
|

which makes sense based on the report. Is modyfing the numbers of 
"#define OMAP3630_VDD_MPU_OPP50_UV1012500" going to actually change the 
operating voltage at 300MHz?

Is there another place the parameters should be modified as well?

I know it may not be supported to tweak the kernel like this, but I am 
wondering at which level it is possible to modify these parameters.

Thanks in advance for any help,

Luis
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