Hi, On Tue, Dec 13, 2016 at 10:02:26AM +0000, Russell King - ARM Linux wrote:
> Is there really any need to do this in head.S ? I believe it's > entirely possible to do it later - arch/arm/mm/nommu.c:paging_init(). As memblock_reserve() for exception address was done before paging_init(), seems it has to be done by arm_mm_memblock_reserve() in arch/arm/mm/nommu.c, WIP patch follows, but not that happy - conditional compilation's make it not so readable, still better to see in C. > Also, if the region setup for the vectors was moved as well, it would > then be possible to check the ID registers to determine whether this > is supported, and make the decision where to locate the vectors base > more dynamically. This would affect Cortex-R's, which is a bit concerning due to lack of those platforms with me, let me try to get it right. Seems translating __setup_mpu() altogether to C & installing at a later, but suitable place might be better. And feeling something strange about Cortex-R support in mainline, don't know whether it boots out of the box, there are no Cortex-R cpu compatibles in dts(i), but devicetree documentation documents it. Still wrecking Cortex-R's could get counted as a regression as dts is not considered Kernel. Looks like there is a Cortex-R mafia around mainline ;) > That leaves one pr_notice() call using the CONFIG_VECTORS_BASE > constant... Seems you want to completely kick out CONFIG_VECTORS_BASE. Saw 2 interesting MMU cases, 1. in devicemaps_init(), if Hivecs is not set, it is being mapped to virtual address zero, was wondering how MMU Kernel can handle exceptions with zero address base (& still prints 0xffff0000 as vector base) 2. One of the platform does a ioremap of CONFIG_VECTORS_BASE Once i take care of the above, the ugly conditional compilation in 3/4th patch (@arch/arm/mm/init.c) of WIP patch series that follows will be removed. Please let know if you have any comments on the above. Also !MMU Kernel could boot on 3 ARM v7-A platforms - AM335x Beagle Bone (A8), AM437x IDK (A9) & Vybrid VF610 (on A5 core, note that it has M4 core too) with same Kernel image*. Vybrid did not need any platform specific tweaks, just 1/2th patch (put in patch system as 8635/1) & WIP series over Vladimir's one, while TI Sitara AMx3's needed one w.r.t remap. Please bear my delay - to fill the stomach, work not on Linux and then the vacations. Regards afzal * Since initramfs was used, tty port had to be changed in initramfs build for Vybrid, but Kernel except for above initramfs change, was identical.
