>-----Original Message----- >From: Kevin Hilman [mailto:khilman@xxxxxxxxxxxxxxxxxxx] >"Pandita, Vikram" <vikram.pandita@xxxxxx> writes: > >>>Vikram Pandita wrote: >>>> This patch cleans up the DEBUG_LL infrastructure for omap boards. >>> >> >> Could you give reference to this code on DaVinci? > >http://git.kernel.org/?p=linux/kernel/git/khilman/linux-davinci.git;a=blobdiff;f=arch/arm/mach- >davinci/include/mach/uncompress.h;h=0f1f12b67875f86232c0e06e1a687a6d7f19b18a;hp=1e27475f9a2322f1a4f61 >e25fd1a1e5858e29fc2;hb=bb9647f44b091ebff17f400bb2a468c7e419f3ac;hpb=0dc6306a65f30c0483cfed9b3e8ee1eb3 >d093e84 > >> >> Yes this is doable, but the question is, how do we pass these variables to the kernel start: >> arch/arm/kernel/head.S >> >> First stage, arch/arm/boot/compressed/head.S gets the arch type -> shift/uart-addr. Fine. >> This stage ends with relocated code over righting the decompressor. >> >> Second stage, arch/arm/kernel/head.S now starts. >> >> I am not sure how to share the data from Stage 1 in this stage? > >This is already taken care of. > >The zImage boot passes the machine-type in a register, then >arch/arm/kernel/head.S uses that to decide which machine to start. >This is where the MACHINE_START/MACHINE_END macros come in to >define the machine-specific hooks called at boot time. Yes. I agree. I have reviewed that path. > >You should use one of the early machine hooks (probably .map_io) >to to set the UART base and shift for the board. I am looking at even earlier than that. The idea is to write to phys_io and io_pg_offset from kernel/head.S very early based on the uart address found in compressed/misc.c To make map_io writable, I will have to change the MACHINE_START to remove the const. It so happens that Russell has defined MACHINE_START to be a const. Not sure is removing const from MACHINE_START is acceptable? I can have a sample implementation and post to get review comments. > >The catch is that between the start of the head.S code and the >mach->map_io hook, printascii() may be called and use the debug >macros to try to print out chars. Care must be taken that >if the UART is not yet known/defined, nothing is printed. That is easy and can be taken care of. > >Kevin > -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
