On Tue, Jan 28, 2020 at 02:55:13PM +0300, Antony Pavlov wrote:
> On Tue, 28 Jan 2020 10:28:32 +0100
> Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx> wrote:
>
> Hi!
>
> Looks like this patch has some undocummented side effects
> (or in other words, it makes undocummented fixups).
>
> I have tested this patch on qemu-malta with current master,
> ee8960aec018df2de ("ARM: imx6: properly check for IPU presence").
> It works fine: memtest works, iomem output looks good.
>
> But the patch fixes several issues and commit message does not contain
> any information about it.
>
> I rebuild current master with qemu-malta_defconfig and MMU enabled.
>
> I used this qemu cmdline to enable qemu monitor:
>
> qemu-system-mips -nodefaults -M malta -m 256 -nographic -bios barebox-flash-image
> -net user -net nic,model=rtl8139 -serial mon:stdio
>
> With '-serial mon:stdio' one can invoke qemu monitor with "ctrl-a c" keypress sequence.
>
> So I tried 'info registers' qemu monitor command after barebox startup:
>
> Hit any to stop autoboot: 3
> barebox@qemu malta:/
> barebox@qemu malta:/
> barebox@qemu malta:/ iomem
> 0x00000000 - 0xffffffff (size 0x00000000) iomem
> 0x180003f8 - 0x180003ff (size 0x00000008) 180003f8.serial@xxxxxxxxxxx
> 0x1e000000 - 0x1e3fffff (size 0x00400000) 1e000000.flash@xxxxxxxxxxx
> 0x1f000900 - 0x1f00093f (size 0x00000040) 1f000900.serial@xxxxxxxxxxx
> 0x1f000b00 - 0x1f000b1f (size 0x00000020) 1f000b00.gpio@xxxxxxxxxxx
> 0x80000000 - 0x8fffffff (size 0x10000000) kseg0_ram0
> barebox@qemu malta:/ QEMU 4.2.0 monitor - type 'help' for more information
> (qemu) info registers
> pc=0xa081232c HI=0x00000026 LO=0x20000000 ds 0090 a081232c 1
> GPR00: r0 00000000 at 00000000 v0 b80003f8 v1 00000000
> GPR04: a0 a0408668 a1 b80003fd a2 b80003f8 a3 ffffffff
> GPR08: t0 00000001 t1 00000000 t2 0000005a t3 00000023
> GPR12: t4 00000000 t5 00010000 t6 00000040 t7 00000010
> GPR16: s0 a0408668 s1 a085cd20 s2 a0860000 s3 a0860000
> GPR20: s4 a0860000 s5 00000400 s6 a08613c0 s7 00000001
> GPR24: t8 00000008 t9 a0812340 k0 00400000 k1 fffffffa
> GPR28: gp 00000000 sp 8fb8fd10 s8 ffffffff ra a0812420
> CP0 Status 0x00000000 Cause 0x00000400 EPC 0x00000000
> Config0 0x80008482 Config1 0x9e190c8f LLAddr 0x0000000000000000
> Config2 0x80000000 Config3 0x00000000
> Config4 0x00000000 Config5 0x00000000
> (qemu) quit
>
> So I see several issues in current master at once:
>
> * iomem output has no information on sdram regions, so memtest is unusable;
> * pc=0xa081232c, relocation does not work, barebox is located with 8M offset
> from start of RAM. The board has 256M and relocation routine
> should move barebox code much higher;
> * pc=0xa081232c, so barebox code works from KSEG1 not from KSEG0 as MMU=y option implies.
>
> Your patch fixes all these symptoms at ones however the commit message
> says nothing about them.
I've tested the patch, everything looks right now:
barebox@qemu malta:/ iomem
0x00000000 - 0xffffffff (size 0x00000000) iomem
0x180003f8 - 0x180003ff (size 0x00000008) 180003f8.serial@xxxxxxxxxxx
0x1e000000 - 0x1e3fffff (size 0x00400000) 1e000000.flash@xxxxxxxxxxx
0x1f000900 - 0x1f00093f (size 0x00000040) 1f000900.serial@xxxxxxxxxxx
0x1f000b00 - 0x1f000b1f (size 0x00000020) 1f000b00.gpio@xxxxxxxxxxx
0x80000000 - 0x8fffffff (size 0x10000000) kseg0_ram0
0x8fb89000 - 0x8fb8ffff (size 0x00007000) stack
0x8fb90000 - 0x8ff8ffff (size 0x00400000) malloc space
0x8ff90000 - 0x8ffeae9f (size 0x0005aea0) barebox
0x8ffeaea0 - 0x8ffefadf (size 0x00004c40) barebox data
0x8fff7ae0 - 0x8fffbbdf (size 0x00004100) bss
barebox@qemu malta:/ whereami
code @ 8ffb9bcc (8ffb9bc0)
data @ 8ffef3c0
bss @ 8fff9ae0
heap @ 8fbb9518
stack @ 8fb8fd50
barebox@qemu malta:/
However I have to enable CONFIG_MMU after `make qemu-malta_defconfig`, or I get
`ERROR: Error: Cannot request SDRAM region for stack`, and no barebox memory
areas in `iomem` output. CONFIG_MMU seems to be enabled for ath79 only:
$ git grep CONFIG_MMU arch/mips/configs/
arch/mips/configs/ath79_defconfig:CONFIG_MMU=y
$
Regards,
Peter
>
> > .bss __rel_start (OVERLAY) was used to optimize RAM size used by
> > barebox. Since .bss and __rel_start overlap, we should clear bss only
> > after __rel_start was used.
> >
> > There is a choice of moving .bss clear sequence after __rel_start or
> > remove this optimization. Since the use of this optimization is minimal
> > and danger to trap in to similar issue is still high, i prefer to remove
> > this optimization.
> >
> > Fixes: 1e5aef61fc6a444 ("MIPS: reloc: init bss and cpu")
> > Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> > ---
> > arch/mips/lib/barebox.lds.S | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/mips/lib/barebox.lds.S b/arch/mips/lib/barebox.lds.S
> > index 693a778980..c954df41f3 100644
> > --- a/arch/mips/lib/barebox.lds.S
> > +++ b/arch/mips/lib/barebox.lds.S
> > @@ -59,7 +59,7 @@ SECTIONS
> >
> > _end = .;
> >
> > - .bss __rel_start (OVERLAY) : {
> > + .bss : {
> > __bss_start = .;
> > *(.sbss.*)
> > *(.bss.*)
> > --
> > 2.25.0
> >
>
>
> --
> Best regards,
> Antony Pavlov
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