On 04/28/2014 12:20 PM, Joel Fernandes wrote: > On 04/28/2014 11:43 AM, Dave Martin wrote: >> On Tue, Apr 22, 2014 at 01:31:46PM -0500, Joel Fernandes wrote: >>> On my DRA7 system, when the kernel is built in THUMB mode, the secondary CPU >>> (Cortex A15) fails to come up causing SMP boot on second CPU to timeout. This >>> seems to be because the CPU is in ARM mode once the ROM hands over control to >>> the kernel. Switch to THUMB mode if required once the kernel is control of >>> secondary CPU. On OMAP4 on the other hand, it appears to be in THUMB mode on >>> entry so this is not required and SMP boot works as is. >>> >>> Cc: Santosh Shilimkar <santosh.shilimkar@xxxxxx> >>> Cc: Russell King <linux@xxxxxxxxxxxxxxxx> >>> Cc: Nishanth Menon <nm@xxxxxx> >>> Cc: Tony Lindgren <tony@xxxxxxxxxxx> >>> Signed-off-by: Joel Fernandes <joelf@xxxxxx> >>> --- >>> arch/arm/mach-omap2/omap-headsmp.S | 8 ++++++-- >>> 1 file changed, 6 insertions(+), 2 deletions(-) >>> >>> diff --git a/arch/arm/mach-omap2/omap-headsmp.S b/arch/arm/mach-omap2/omap-headsmp.S >>> index 75e9295..1809dce 100644 >>> --- a/arch/arm/mach-omap2/omap-headsmp.S >>> +++ b/arch/arm/mach-omap2/omap-headsmp.S >>> @@ -1,7 +1,7 @@ >>> /* >>> * Secondary CPU startup routine source file. >>> * >>> - * Copyright (C) 2009 Texas Instruments, Inc. >>> + * Copyright (C) 2014 Texas Instruments, Inc. >>> * >>> * Author: >>> * Santosh Shilimkar <santosh.shilimkar@xxxxxx> >>> @@ -28,9 +28,13 @@ >>> * code. This routine also provides a holding flag into which >>> * secondary core is held until we're ready for it to initialise. >>> * The primary core will update this flag using a hardware >>> -+ * register AuxCoreBoot0. >>> + * register AuxCoreBoot0. >>> */ >>> ENTRY(omap5_secondary_startup) >> >> Are you sure this problem is not caused by the missing ENDPROC() for >> omap5_secondary_startup? >> >> You have END() instead (which may have been accidental). >> >> Without ENDPROC(), the symbol is not marked as a function and so >> the Thumb bit won't be set when taking a pointer -- so the kernel >> is actually telling the firmware to enter in ARM state. >> >> >> Try changing END() to ENDPROC() without this patch, and see if it >> makes a difference. >> >> If it still doesn't work, then the firmware either doesn't support >> entering in ARM, or is buggy. > > Thanks for the suggestion. I'm guessing what you mean is with ENDPROC, > interworking code uses bx instead of bl to set thumb mode. > > But ROM/firmware doesn't have access to symbol table, how would it know > the type of the symbol to be ARM or THUMB before it branches? > Sorry what I meant is, say its of Type function. What tells the firmware to switch to THUMB? What's typically done is a boot address register is written by the kernel, and the firmware jumps to it after WFE. thanks, -Joel -- 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
