[U-Boot] [PATCH] imx: don't clobber reset cause

[Bill Pringlemeir <bpringlemeir@nbsps.com>]

On  4 Feb 2015, eric.nelson at boundarydevices.com wrote:

> The cause of a reset is generally useful, and shouldn't be
> blindly cleared in the process of displaying it as a part
> of the boot announcement.
>
> If a particular system wants to clear it out, this should
> be done later after there's an opportunity for code or
> boot commands to read the value.
>
> Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
> ---
> arch/arm/imx-common/cpu.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/arch/arm/imx-common/cpu.c b/arch/arm/imx-common/cpu.c
> index 28ccd29..3e0a582 100644
> --- a/arch/arm/imx-common/cpu.c
> +++ b/arch/arm/imx-common/cpu.c
> @@ -30,7 +30,6 @@ char *get_reset_cause(void)
> 	struct src *src_regs = (struct src *)SRC_BASE_ADDR;
>
> 	cause = readl(&src_regs->srsr);
> -	writel(cause, &src_regs->srsr);
>
> 	switch (cause) {
> 	case 0x00001:

There is very similar code in 'arch/arm/cpu/armv7/vf610/generic.c'.  The
write is for a hard power on case where these reason registers are full
of weird bogus values (at least on Vybrid; I suspect on iMx).  In the
case of a non-POR, the register bits are good.  However, if you don't
clear the status, on the next reset it may have multiple registers bits
even though you really want to know the last reason (bit).

Another option would be to clear the value and store the 'cause'
somewhere for other U-Boot users.  Unless you wanted to read this from
an OS?  I think both files should behave the same, all else equal.

Fwiw,
Bill Pringlemeir.