* Is it possible to change the operating voltage at a particular frequency for BBxM
[not found] <52027A39.3070700@ecs.soton.ac.uk>
@ 2013-08-07 16:47 ` Luis Alfonso Maeda-Nunez
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From: Luis Alfonso Maeda-Nunez @ 2013-08-07 16:47 UTC (permalink / raw)
To: meta-ti
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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@arm:/# cat /sys/class/regulator/regulator.4/name
vdd_mpu_iva
root@arm:/# cat /sys/class/regulator/regulator.4/microvolts
1012500
root@arm:/# cat /sys/class/regulator/regulator.4/max_microvolts
1450000
root@arm:/# cat /sys/class/regulator/regulator.4/min_microvolts
600000
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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
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/* 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),
};
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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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