[U-Boot] [PATCH] arm: socfpga: dm: Fix DM initialization failure after warm reset

[Marek Vasut <marex@denx.de>]

On Friday, September 04, 2015 at 04:16:21 PM, Simon Glass wrote:
> Hi,
> 
> On 4 September 2015 at 01:36, Jian Luo <Jian.Luo4@boschrexroth.de> wrote:
> > Hi Simon,
> > 
> > On 04.09.2015 02:23, Simon Glass wrote:
> >> Hi,
> >> 
> >> On 3 September 2015 at 05:14, Marek Vasut <marex@denx.de> wrote:
> >>> On Thursday, September 03, 2015 at 01:12:03 PM, Jian Luo wrote:
> >>>> On 03.09.2015 12:46, Marek Vasut wrote:
> >>>>  > On Thursday, September 03, 2015 at 12:17:13 PM, Jian Luo wrote:
> >>>>  > 
> >>>>  > Hi!
> >>>>  > 
> >>>>  > [...]
> >>>>  > 
> >>>>  >>  >> Yes, I can. But U-Boot can still have problem with other Image
> >>>>  >>  >> which disables ECC.
> >>>>  >>  >> I found another post related to this problem
> >>>>  >>  >> https://lkml.org/lkml/2015/2/6/685 .
> >>>>  >>  >> 
> >>>>  >>  >>      Quote: To initialize ECC, the OCRAM needs to enable ECC
> >>>> 
> >>>> then clear
> >>>> 
> >>>>  >>  >> the entire
> >>>>  >>  >> 
> >>>>  >>  >>      memory to zero before using it.
> >>>>  >> 
> >>>>  >> Hi!
> >>>>  >> 
> >>>>  >>  > Oh, but that is a problem, since we're running from the OCRAM
> >>>> 
> >>>> ourselves,
> >>>> 
> >>>>  >>  > thus we cannot clear the OCRAM. Maybe we should force-disable
> >>>>  >>  > the ECC instead? But can we be sure that the corruption does
> >>>>  >>  > not
> >>>> 
> >>>> happen
> >>>> 
> >>>>  >>  > when you disable ECC ?
> >>>>  >> 
> >>>>  >> Yes, that will be a problem. It's also why I let the
> >>>>  >> SYSMGR_ECC_OCRAM_EN bit intact in the patch.
> >>>>  > 
> >>>>  > OK, but what about turning the ECC off in the SPL, will that also
> >>>> 
> >>>> introduce
> >>>> 
> >>>>  > corruption or not ? That might be the right fix, no ?
> >>>> 
> >>>> Hi Marek,
> >>>> 
> >>>> Sorry, I don't know the detail of ECC implementation in socfpga.
> >>>> Dinh might have the answer to that.
> >>>> 
> >>>> Anyhow I still think let the setting untouched is the safest fix.
> >>>> SPL should use the same ECC setting which BROM loads SPL with.
> >>> 
> >>> That's right, but I'd also like to have this bit in some defined
> >>> state from the boot instead of having this in some random setting.
> >>> Dinh, can you comment on this corruption please ?
> >> 
> >> Also I'm still a bit confused.
> >> 
> >> The code in crt0.S zeroes global_data so how can it be non-zero a
> >> little later in board_init_f()?
> > 
> > board_init_f() enables the ECC of the SRAM regardless its previous state.
> > If ECC is disabled beborehand, re-enabling it can cause SRAM misreading.
> 
> OK thanks. It might be possible to do this earlier, say in cpu_init_crit().

You cannot enable the bit, because it'd corrupt your OCRAM and your code is
running from the OCRAM, thus you'd be susceptible to corrupting the code
you're running itself :(