Hi, I'm tying to port the PREEMPT_RT patch to AR71xx CPU family; this kind of CPU are MIPS. I'm using the last revision of OpenWrt Linux distro. The platform can be added into the kernel using the files that you can download form https://dev.openwrt.org/browser/trunk/target/linux/ar71xx/files. These are the steps done: 0) I to build the Kernel with the OpenWrt patches delete (only to perform some tests...) the patch 110-netfilter_match_speedup.patch and the 200-sched_esfq.patch from ./trunk/target/linux/generic-2.6/patches-2.6.31/ folder. I used the kernel 2.6.31.12. 1) copy into the ./trunk/target/linux/generic-2.6/patches-2.6.31/ the http://www.kernel.org/pub/linux/kernel/projects/rt/patch-2.6.31.12-rt20.gz patch (RT20) 2) when you build the kernel you will have a problem at line 1852 of the file ./fs/yaffs2/yaffs_fs.c (that you will find in the kernel of OpenWrt distro): I replaced the init_MUTEX(&dev->grossLock) with semaphore_init(&dev->grossLock). Now you can build the kernel. 3) I also changed the specific drivers as reported in http://www.celinuxforum.org/CelfPubWiki/JapanTechnicalJamboree14?action=AttachFile&do=get&target=preempt070427celfjambo14.pdf: spin_lock, etc... 4) when you boot the kernel in a device (I tested it with an Ubiquiti RouterStation) you will have a kernel panic. Look at arch/mips/ar71xx/irq.c, you have a kernel panic when you call setup_irq(....) with struct irqaction with ".handler = no_action". For this reasons if you comment out the lines 98, 175, 261 and 359 the kernel boots. Q1) Is this fix correct? 5) the problem now is the filesystem; I can use: jffs2, yaffs or squashfs. I'd link to use the jffs2, it can be mounted without kernel panics but I have a lot pf problems: 5.1) the fs operations (the OpenWrt first boot initialisation performed by the kernel) are very slow. 5.2) the init script are not called propriety: only some services starts. I know that I have many problems with this device but if you want cooperate in the porting or guide me in this experiment are wellcome. Regards Andrea -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
