I have a QCA4531 development board with linux kernel of 3.14.0 and custom image, so i can only install packages from downloads.openwrt.org/barrier_breaker/14.07-rc3/ar71xx/generic/packages but in this i don't find all the suitable packages for my application. So i want to upgrade the kernel to 3.18.20 so that i can install packages from downloads.openwrt.org/chaos_calmer/15.05.1/ar71xx/generic/packages/packages here.

So i need some information how to upgrade the Linux kernel and need the kernel.bin, rootfs-squashfs.bin and squashfs-sysupgrade.bin images to flash it to the QCA4531 board.

The output of uname -a
root@OpenWrt:~# uname -a
Linux OpenWrt 3.14.0 #2 Fri Mar 4 10:44:04 CST 2016 mips GNU/Linux

root@OpenWrt:~# cat /etc/openwrt_release
DISTRIB_ID="QSDK"
DISTRIB_RELEASE="NHSS.ILQ"
DISTRIB_REVISION="r40838"
DISTRIB_CODENAME="ioe_device"
DISTRIB_TARGET="ar71xx/generic"
DISTRIB_DESCRIPTION="QSDK IoE Device NHSS.ILQ"
DISTRIB_TAINTS="no-all busybox override"

are there any differences between that one and QCA9531? why not backport the package you miss there or look when it's support was dropped and manually patch.

are there any differences between that one and QCA9531? why not backport the package you miss there or look when it's support was dropped and manually patch.

There is not much difference between QCA9531 and QCA4531. In order to use packages from Chaos Calmer 15.05 the linux kernel should be 3.18 which i need to upgrade on my board. In Chaos calmer still it shows it supports for AR71xx boards configuration. I tried to upgrade the kernel by patch but doesnt work.

So looking for a proper kernel upgrade procedure.

The only way to upgrade your kernel is by flashing a newer firmware image.