On Sat, Feb 16, 2013 at 12:14:49AM -0500, Nicolas Pitre wrote: > On Fri, 15 Feb 2013, Russell King - ARM Linux wrote: > > > On Thu, Feb 14, 2013 at 11:47:50PM +0100, Arnd Bergmann wrote: > > > Patch c08e20d24 "arm: Add v7_invalidate_l1 to cache-v7.S" > > > moves the v7_invalidate_l1 symbol out of imx/headsmp.S, > > > which seems to cause a link error because it is now > > > too far away from v7_cpu_resume when building an > > > allyesconfig kernel. > > > > > > If we move the v7_cpu_resume function from the .data > > > section to .text, that creates another link error > > > for the reference to phys_l2x0_saved_regs, but we > > > can move all of the above to .text. > > > > > > I believe that this is not a correct bug fix but just > > > a bad workaround, so I'm open to ideas from people > > > who understand the bigger picture. > > > > Unfortunately, this ends up with writable data in the .text section, which > > is supposed to be read-only. We should try to preserve that status, even > > though we don't enforce it. > > > > I guess the problem is that we end up with the .data segment soo far away > > from the .text segment that these branches no longer work (and remember > > that this code executes with the MMU off.) > > > > The only solution I can think is that we need to do quite a bit of magic > > here to jump to an absolute address, but taking account of the V:P offset. > > That's not going to be particularly nice, and it's going to then also have > > to jump back the other way - to the cpu_resume code which is also in the > > .data section. > > Something like this should work: > > diff --git a/arch/arm/mach-imx/headsmp.S b/arch/arm/mach-imx/headsmp.S > index 7e49deb128..9de26f3edb 100644 > --- a/arch/arm/mach-imx/headsmp.S > +++ b/arch/arm/mach-imx/headsmp.S > @@ -99,8 +99,11 @@ phys_l2x0_saved_regs: > #endif > > ENTRY(v7_cpu_resume) > - bl v7_invalidate_l1 > + ldr ip, 2f > + mov lr, pc > +1: add pc, pc, ip > pl310_resume > b cpu_resume > +2: .word v7_invalidate_l1 - 1b - 8 > ENDPROC(v7_cpu_resume) > #endif > Yes, it works.
> > However it is probably best to move all the code to the .text section > where it belongs and fixup the data access instead. I must plead guilty > for introducing this idea of putting code in the .data section with the > SA1100resume code over 10 years ago that everyone copied since. > > So here's how I think it should look instead, and how I should have done > the SA1100 code back then: > > diff --git a/arch/arm/mach-imx/headsmp.S b/arch/arm/mach-imx/headsmp.S > index 7e49deb128..38a544a037 100644 > --- a/arch/arm/mach-imx/headsmp.S > +++ b/arch/arm/mach-imx/headsmp.S > @@ -73,16 +73,16 @@ ENDPROC(v7_secondary_startup) > > #ifdef CONFIG_PM > /* > - * The following code is located into the .data section. This is to > - * allow phys_l2x0_saved_regs to be accessed with a relative load > - * as we are running on physical address here. > + * The following code must assume it is running from physical address > + * where absolute virtual addresses to the data section have to be > + * turned into relative ones. > */ > - .data > - .align > > #ifdef CONFIG_CACHE_L2X0 > .macro pl310_resume > - ldr r2, phys_l2x0_saved_regs > + adr r0, phys_l2x0_saved_ptr_offset > + ldr r2, [r0] > + add r2, r2, r0 > ldr r0, [r2, #L2X0_R_PHY_BASE] @ get physical base of l2x0 > ldr r1, [r2, #L2X0_R_AUX_CTRL] @ get aux_ctrl value > str r1, [r0, #L2X0_AUX_CTRL] @ restore aux_ctrl > @@ -90,9 +90,13 @@ ENDPROC(v7_secondary_startup) > str r1, [r0, #L2X0_CTRL] @ re-enable L2 > .endm > > + .bss > .globl phys_l2x0_saved_regs > phys_l2x0_saved_regs: > - .long 0 > + .space 4 > + .previous > +phys_l2x0_saved_ptr_offset: > + .word phys_l2x0_saved_regs - . > #else > .macro pl310_resume > .endm > But this does not work. It seems the execution jumps to the start of kernel on system resuming. Shawn root@freescale ~$ ./rtcwakeup.sh rtcwakeup.out: wakeup from "mem" using rtc0 at Fri Jan 2 00:09:43 1970 PM: Syncing filesystems ... done. PM: Preparing system for mem sleep mmc0: card a8a5 removed mmc1: card b368 removed Freezing user space processes ... (elapsed 0.01 seconds) done. Freezing remaining freezable tasks ... (elapsed 0.01 seconds) done. PM: Entering mem sleep fec_stop : Graceful transmit stop did not complete ! PM: suspend of devices complete after 8.361 msecs PM: suspend devices took 0.010 seconds PM: late suspend of devices complete after 0.267 msecs PM: noirq suspend of devices complete after 0.754 msecs Disabling non-boot CPUs ... CPU1: shutdown CPU2: shutdown CPU3: shutdown Booting Linux on physical CPU 0x0 Linux version 3.8.0-rc7-next-20130215+ (r65073@S2101-09) (gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) ) #341 SMP Mon Feb 18 13:36:48 CST 2013 CPU: ARMv7 Processor [412fc09a] revision 10 (ARMv7), cr=10c53c7d CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache Machine: Freescale i.MX6 Quad (Device Tree), model: Freescale i.MX6 Quad SABRE Lite Board Memory policy: ECC disabled, Data cache writealloc -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
