sjg@google.com schrieb am 01.06.2017 05:11:57:
hannes.schmelzer@br-automation.com wrote:
With this commit we can modify single values within an array of a dts property.
This is useful if we have for example a pwm-backlight where we want to modifiy the pwm frequency per u-boot script.
The pwm is described in dts like this:
backlight { pwms = <0x0000002b 0x00000000 0x004c4b40>; };
For changing the frequency, here the 3rd parameter, we simply type:
fdt set /backlight pwms <? ? 0x1E8480>;
For doing all this we:
- backup the property content into our 'SCRATCHPAD'
- only modify the array-cell if the new content doesn't start with '?'
Signed-off-by: Hannes Schmelzer hannes.schmelzer@br-automation.com
cmd/fdt.c | 29 +++++++++++++++++++++-------- 1 file changed, 21 insertions(+), 8 deletions(-)
Reviewed-by: Simon Glass sjg@chromium.org
I imagine this would have to be done before setting 'stdout' to 'vidconsole' so that the PWM is not inited before this script runs.
Yes, if lcd output is used already in u-boot this is correct. For my case i don't have any output in u-boot, but later on within linux environment.
But setting some pwm frequency is only one example for using this, every other array-property can also be modified with this.
cheers, Hannes