[U-Boot] [PATCH] MIPS: Hang if run on a secondary CPU

[Daniel Schwierzeck]

Hi Paul,

Am 21.09.2016 um 12:08 schrieb Paul Burton:
> Some systems are configured such that multiple CPUs begin running from
> their reset vector following a system reset. If this occurs then U-Boot
> will be run on multiple CPUs simultaneously, which causes all sorts of
> issues as the multiple instances of U-Boot clobber each other.
> 
> Prevent this from happening by simply hanging with an infinite loop if
> we run on a CPU whose ID, as determined by GlobalNumber or EBase.CPUNum
> as appropriate, is non-zero.
> 
> Signed-off-by: Paul Burton <paul.burton at imgtec.com>

just a tipp: please try to use patman with -m to disable automatic
generation of the CC list and configure the CC addresses manually in the
patches. Your CC list is always bigger than needed. I doubt that most of
the guys care about MIPS low-level stuff ;)

Also please rebase this and your other patch on top of u-boot-mips/next.
I'm getting conflicts when applying. Thanks.

> ---
> 
>  arch/mips/cpu/start.S            | 25 +++++++++++++++++++++++++
>  arch/mips/include/asm/mipsregs.h |  7 +++++++
>  2 files changed, 32 insertions(+)
> 
> diff --git a/arch/mips/cpu/start.S b/arch/mips/cpu/start.S
> index fc6dd66..dd37ac3 100644
> --- a/arch/mips/cpu/start.S
> +++ b/arch/mips/cpu/start.S
> @@ -112,6 +112,31 @@ ENTRY(_start)
>  
>  	.align 4
>  reset:
> +#if __mips_isa_rev >= 6
> +	.set	push
> +	.set	reorder
> +	mfc0	t0, CP0_CONFIG, 1
> +	bgez	t0, 1f
> +	mfc0	t0, CP0_CONFIG, 2
> +	bgez	t0, 1f
> +	mfc0	t0, CP0_CONFIG, 3
> +	bgez	t0, 1f
> +	mfc0	t0, CP0_CONFIG, 4
> +	bgez	t0, 1f
> +	mfc0	t0, CP0_CONFIG, 5
> +	and	t0, t0, MIPS_CONF5_VP
> +	beqz	t0, 1f
> +
> +	mfc0	t0, CP0_GLOBALNUMBER
> +	b	2f
> +	.set	pop
> +#endif
> +
> +1:	mfc0	t0, CP0_EBASE
> +	and	t0, t0, EBASE_CPUNUM
> +
> +	/* Hang if this isn't the first CPU in the system */
> +2:	bnez	t0, .

What about the branch delay slot? start.S is globally set to .noreorder
and this particular branch instruction is also used for MIPS < r6

>  
>  	/* Clear watch registers */
>  	MTC0	zero, CP0_WATCHLO
> diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h
> index 3185dc7..9a4c4c5 100644
> --- a/arch/mips/include/asm/mipsregs.h
> +++ b/arch/mips/include/asm/mipsregs.h
> @@ -39,6 +39,7 @@
>  #define CP0_ENTRYLO0 $2
>  #define CP0_ENTRYLO1 $3
>  #define CP0_CONF $3
> +#define CP0_GLOBALNUMBER $3, 1
>  #define CP0_CONTEXT $4
>  #define CP0_PAGEMASK $5
>  #define CP0_WIRED $6
> @@ -361,6 +362,11 @@
>  #define CAUSEF_BD		(_ULCAST_(1)   << 31)
>  
>  /*
> + * Bits in the coprocessor 0 EBase register.
> + */
> +#define EBASE_CPUNUM		0x3ff
> +
> +/*
>   * Bits in the coprocessor 0 config register.
>   */
>  /* Generic bits.  */
> @@ -548,6 +554,7 @@
>  #define MIPS_CONF5_MRP		(_ULCAST_(1) << 3)
>  #define MIPS_CONF5_LLB		(_ULCAST_(1) << 4)
>  #define MIPS_CONF5_MVH		(_ULCAST_(1) << 5)
> +#define MIPS_CONF5_VP		(_ULCAST_(1) << 7)
>  #define MIPS_CONF5_FRE		(_ULCAST_(1) << 8)
>  #define MIPS_CONF5_UFE		(_ULCAST_(1) << 9)
>  #define MIPS_CONF5_MSAEN	(_ULCAST_(1) << 27)
> 

-- 
- Daniel

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 473 bytes
Desc: OpenPGP digital signature
URL: <http://lists.denx.de/pipermail/u-boot/attachments/20160921/8fd67021/attachment.sig>