[U-Boot] [PATCH] i.MX28: Add delay after CPU bypass is cleared

[Stefano Babic <sbabic@denx.de>]

On 04/05/2012 13:32, Marek Vasut wrote:
> This solves issues when larger amount of DRAM is used, like 256MB.
> Behave the same in case of CPU bypass as we do in case of EMI
> bypass, but wait 15 ms. We need to wait until the clock domain
> stabilizes.
> 
> This issue seemed to have been caused by not waiting after frobbing
> with the CPU bypass, it was unrelated to memory, but had a direct
> impact, causing trouble. This was yet another X-File of the
> imx-bootlets, sigh. The conclusion is, trying a semi-random delay
> (there is delay after the EMI bypass change), the issue is fixed.
> 
> Another possible explanation is that we do not do the "simple memory
> test" FSL does in their imx-bootlets (1000 R/W cycles to/from piece of
> the memory, while also outputing something on the serial port). This
> might have caused the similar delay in the imx-bootlets and therefore
> they didn't need to add this explicitly.
> 
> For now, this seems good fix enough, but to me, whole that memory
> init code in imx-bootlets is completely flunked and it'd need deeper
> investigation.
> 
> Signed-off-by: Marek Vasut <marex@denx.de>
> Cc: Wolfgang Denk <wd@denx.de>
> Cc: Detlev Zundel <dzu@denx.de>
> Cc: Stefano Babic <sbabic@denx.de>
> Cc: Fabio Estevam <festevam@gmail.com>
> ---
>  arch/arm/cpu/arm926ejs/mx28/spl_mem_init.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> V2: Change the description, this issue seemed to have been caused by not
>     waiting after frobbing with the CPU bypass, it was unrelated to memory,
>     but had a direct impact, causing trouble. This was yet another X-File
>     of the imx-bootlets, sigh.
> V3: Add more conspiracy theories into the commit message.
> 
> diff --git a/arch/arm/cpu/arm926ejs/mx28/spl_mem_init.c b/arch/arm/cpu/arm926ejs/mx28/spl_mem_init.c
> index 0d13537..9fa5d29 100644
> --- a/arch/arm/cpu/arm926ejs/mx28/spl_mem_init.c
> +++ b/arch/arm/cpu/arm926ejs/mx28/spl_mem_init.c
> @@ -149,6 +149,8 @@ void mx28_mem_setup_cpu_and_hbus(void)
>  	/* Disable CPU bypass */
>  	writel(CLKCTRL_CLKSEQ_BYPASS_CPU,
>  		&clkctrl_regs->hw_clkctrl_clkseq_clr);
> +
> +	early_delay(15000);
>  }
>  

It is fine with me

Acked-by: Stefano Babic <sbabic@denx.de>

Best regards,
Stefano Babic

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