Hi All,
I have very basic question. I want to pass few u-boot parameters (other then bootargs) to kernel.
We are using kernel 3.14.28. I have used ATAG mechanism in kernel 2.6.37 but seems that things have got changed.
Any examples or reference code related to kernel 3.14.28 will be appreciated.
Thanks,
Jemish
you can use chosen in DT
linux/Documentation/devicetree/usage-model.txt
178 2.3 Runtime configuration
179 -------------------------
180 In most cases, a DT will be the sole method of communicating data from
181 firmware to the kernel, so also gets used to pass in runtime and
182 configuration data like the kernel parameters string and the location
183 of an initrd image.
184
185 Most of this data is contained in the /chosen node, and when booting
186 Linux it will look something like this:
187
188 chosen {
189 bootargs = "console=ttyS0,115200 loglevel=8";
190 initrd-start = <0xc8000000>;
191 initrd-end = <0xc8200000>;
192 };
193
194 The bootargs property contains the kernel arguments
Hi Biyong Sun,
I have a question for the Communication between Kernel and U-boot.
I want to know how to send the just 1bit data between kernel and u-boot.
Could you tell me how to do that?
Actually I have to perform the below action in kernel and u-boot.
1) In kernel, set or clear a 1-bit flag in some space.
2) In U-boot, U-boot perform some action base on the 1-bit falg
2-1) Perform A action when the 1-bit flag is "0".
2-2) Perform B action when the 1-bit flag is "1".
Best Regards,
Eric.
Hi,
One more thing while reading kernel Documentation I come to know that we can either pass tag list or flattened device-tree block.
In this case how can we pass u-boot parameters to kernel.
Thanks,
Jemish
Hi Jemish,
You can pass the u-boot parameters by command "setenv bootargs <your argumets>" from u-boot terminal. After boot the kernel you can read it by "cat /proc/cmdline". The official images for i.MX6/7 support device tree and bootargs in default for all new kernels.
Martin
Hi Martin,
Thanks for your quick response!
Is bootargs only way to pass u-boot parameters to kernel or is there any other option ?
Because in case of ATAG mechanism I am able to pass u-boot parameters without adding it in bootargs?
Thanks,
Jemish