[U-Boot] [PATCH 3/4 V2] i.MX28: Add delay after CPU bypass is cleared

[Marek Vasut]

Dear Stefano Babic,

> On 03/05/2012 17:47, Marek Vasut wrote:
> > This solves issues when larger amount of DRAM is used. Behave the
> > same in case of CPU bypass as we do in case of EMI bypass, wait
> > 15 ms. We need to wait until the clock domain stabilizes.
> > 
> > Signed-off-by: Marek Vasut <marex at denx.de>
> > Cc: Wolfgang Denk <wd at denx.de>
> > Cc: Detlev Zundel <dzu at denx.de>
> > Cc: Stefano Babic <sbabic at denx.de>
> > Cc: Fabio Estevam <festevam at gmail.com>
> > ---
> > 
> > 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.
> >  
> >  arch/arm/cpu/arm926ejs/mx28/spl_mem_init.c |    2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/arch/arm/cpu/arm926ejs/mx28/spl_mem_init.c
> > b/arch/arm/cpu/arm926ejs/mx28/spl_mem_init.c index 0d13537..a9b1bb6
> > 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);
> 
> Is there some influence (I assume that from your commit message) between
> size of the RAM and amount of time to wait ?

Nope

> Then yes, with boards with
> even more memory (this patch touches a common MX28 file) this delay is
> not enough. Should we correlate the delay maybe with PHYS_SDRAM_1_SIZE
> (maybe early_delay(15000 * (PHYS_SDRAM_1_SIZE / 512MB)) ?

There was a new version of this patch explaining how I got to this delay (or how 
FSL hid it from me).

> 
> Best regards,
> Stefano Babic

Best regards,
Marek Vasut