[U-Boot] ELF_RELOC causes strange I-cache issues

[Heiko Schocher <hs@denx.de>]

Hello Albert,

Albert Aribaud wrote:
> Wolfgang (and others who can/want),
> 
> Please test this patch; it should add a complete barrier to make
> sure that all fixups are written to RAM before jumping there, and
> that no remnants subsist of the old unfixed code in the instruction
> paths. However, I cannot even do basic testing on it as I have
> no 1136 board, so I cannot rule out even basic mistakes.
> 
> When this works I'll do a proper [PATCH].
> 
> Amicalement,
> Albert.
> 
> diff --git a/arch/arm/cpu/arm1136/start.S b/arch/arm/cpu/arm1136/start.S
> index 8b63192..f49f1de 100644
> --- a/arch/arm/cpu/arm1136/start.S
> +++ b/arch/arm/cpu/arm1136/start.S
> @@ -257,6 +257,11 @@ fixloop:
>  	add	r2, r2, #4
>  	cmp	r2, r3
>  	bne	fixloop
> +	/* fixups done, cleanup caches if used and prefetch buffer */
> +	mov	r3, #0
> +	mcr	p15, 0, r3, c7, c10, 4	/* data synchronization barrier */
> +	mcr	p15, 0, r3, c7, c5, 0	/* invalidate instruction cache */
> +	mcr	p15, 0, r3, c7, c5, 4	/* flush prefetch buffer */
>  #endif
>  #endif	/* #ifndef CONFIG_SKIP_RELOCATE_UBOOT */

Actually I tried an identically patch, but didn;t help :-(

But as reading in the arm manual such a memory barrier should
not be bad here ...

BTW:

I had a fix for this problem, but I completly not understand
what it has to do with relocation (if it really is a problem
introduced through relocation ...), nor why a flush_cache
helps here, because dcache is off and only icache is on ...

diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index f44fc4e..3e326ac 100644
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -203,6 +203,8 @@ static inline void ehci_invalidate_dcache(struct QH *qh)
 static int handshake(uint32_t *ptr, uint32_t mask, uint32_t done, int usec)
 {
        uint32_t result;
+
+       flush_cache(0, 0);
        do {
                result = ehci_readl(ptr);
                if (result == ~(uint32_t)0)

and the "usb read 80000000 0 1000" command works fine ...


Maybe Icache flush dosen;t work because the "ARM1136 Errata 411920
Invalidate Instruction Cache operation can fail" interferes here?

bye,
Heiko
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