Specify CPU Frequency as a Kernel Cmd_Line Parameter of Linux on Boot

HOW TO FORCEFULLY DISABLE intel_pstate? intel_pstate is enabled on reboot even with intel_pstate=disable option in grub

sorry to post this as an answer but I don't have the reputation to post as a comment :/

I had the same problem when trying to disable intel_pstate driver in my intel core i7. While managing to disable it, acpi-cpufreq was not loading properly, the problem being SpeedStep was disabled. SpeedStep allows the frequency to be changed by software in these microprocessors, with it disabled it can only be touched by the hardware. You can access this option through BIOS settings. I hope that helps!

Understanding the perf report

Zulan is quite close and all his suggestions should be followed through.

From the man page of perf report:

The command column in the perf report output refers to the process from which the samples were collected. In per-thread/per-process mode, this is always the name of the monitored command. But in cpu-wide mode, the command can vary.

Because you are measuring per-cpu context switch events as can be seen from your perf record ... -cpu=8... command, the perf report command will start to report PID/TID of next/prev task. You can see this here -

per-cpu context switch records pid/tid

Now the value -1 refers to a process which is dead, i.e. the process has gone beyond the state of being a zombie process. This means the task_struct members now point to already freed memory and no dereferencing should be allowed.The do_task_dead method should clearly reflect this.
This is where the pid of the process is being returned as -1 and simultaneously reported in perf report.

There is an extensive discussion on this problem. Initially a value of 0 used to refer to such a process state in the perf report output but as you may have guessed, pid=0 refers to the idle thread and hence a value of -1 is used.

Google maps API v3 places search - pass in another parameter to callback function

How about the following:

service.search(req_bank, function (results, status) {
  locations(results, status, "bank");
});

function locations(results, status, type) {
  if (status == google.maps.places.PlacesServiceStatus.OK) {
    // check the type to determine the marker, or pass a url to the marker icon
  }
}

Raspberry Pi 4 U-Boot on booting hanging in Starting Kernel

I had the same confusing problem on raspberry pi 4 and finally I found out solution.

1. Make sure "enable_uart=1" is in config.txt in first partition.

2. Raspberry pi 4 supports both 32-bit and 64-bit mode. The firmware config.txt, u-boot and kernel should be same configuration.

Here is my config.txt for 64-bit system.

[pi4]
kernel=u-boot.bin
max_framebuffers=2

[all]
arm_64bit=1
enable_uart=1
dtparam=i2c=on
dtparam=spi=on
dtparam=act_led_trigger=heartbeat
dtparam=pwr_led_trigger=mmc0
dtparam=audio=on
device_tree_address=0x02000000
dtoverlay=vc4-fkms-v3d,cma-128

Just remove "arm_64bit=1" for 32-bit system, working with 32-bit u-boot and kernel and device tree binary (dtb).

Please make sure you're using correct toolchain for each system.

Here is my toolchain for u-boot, kernel and buildroot:

64-bit: gcc-linaro-7.5.0-2019.12-x86_64_aarch64-linux-gnu
32-bit: gcc-linaro-7.5.0-2019.12-x86_64_arm-linux-gnueabihf

3. Add "8250.nr_uarts=1" in u-boot bootargs. Then you'll get full kernel boot log, and it will help you to find out where it is stuck.

Here is my bootargs to load rootfs on second partition.

setenv bootargs 8250.nr_uarts=1 console=ttyS0,115200 root=/dev/mmcblk0p2 rootwait rw

4. Load kernel and device tree, and start kernel

For 64-bit system

fatload mmc 0:1 ${kernel_addr_r} Image
fatload mmc 0:1 ${fdt_addr} bcm2711-rpi-4-b.dtb
booti ${kernel_addr_r} - ${fdt_addr}

For 32-bit system

fatload mmc 0:1 ${kernel_addr_r} zImage
fatload mmc 0:1 ${fdt_addr} bcm2711-rpi-4-b.dtb
bootz ${kernel_addr_r} - ${fdt_addr}

Note that we need use fdt_addr instead of fdt_addr_r, although fdt_addr_t also works for me. See https://elinux.org/RPi_U-Boot for fdt_addr vs fdt_addr_t.

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