[U-Boot] [PATCH] ARM: socfpga: Remove socfpga_sdram_apply_static_cfg()

[Ley Foon Tan]

On Mon, Mar 9, 2020 at 10:10 PM Simon Goldschmidt
<simon.k.r.goldschmidt at gmail.com> wrote:
>
> On Mon, Mar 9, 2020 at 1:57 PM Marek Vasut <marex at denx.de> wrote:
> >

> > >>
> > >
> > > I can reproduce the issue if without setting applycfg bit. Access to
> > > F2sdram interface will cause system hang.
> > >
> > > From the Cyclone 5 Soc datasheet:
> > > applycfg - Write with this bit set to apply all the settings loaded in
> > > SDR registers to the memory interface. This bit is write-only and
> > > always returns 0 if read.
> > >
> > > Software should set applycfg bit if change any register under SDR
> > > register range. SW is allowed to set this bit multiple times, the only
> > > condition is SDRAM need to be idle.
> > > My suggestion is we add back socfpga_sdram_apply_static_cfg(), but
> > > change the sequence to below:
> > > writel(iswgrp_handoff[3], &sdr_ctrl->fpgaport_rst);
> > > socfpga_sdram_apply_static_cfg();
> > >
> > > Marek and Simon, are you okay with this? If yes, I will submit patch for this.
> >
> > The problem was that this was causing weird sporadic hangs on Gen5,
> > which is why it was removed. So until there is an explanation for those
> > hangs, I'm not really OK with this.
>
> These sporadic hangs you saw were on devices without an FPGA image directly
> accessing the SDRAM ports, right?
>
> >
> > Maybe the application of static config should happen in SPL, before the
> > DRAM is running, or something like that ?
>
> Thinking this further, limiting it to applying in SPL is not a good idea since
> that prevents us from implementing different FPGA images/configs by loading a
> config later in the boot (i.e. in U-Boot from a FIT-image).
>
> Would it work to make setting this optional, i.e. only write the bit if an FPGA
> config actually uses these ports? Then it couldn't lead to problems on other
> hardware...

If the sporadic hangs issue happen on FPGA image that doesn't connect
to f2sdram interface, we can add the checking to only apply static cfg
when it has f2sdram port enabled.
It can send a patch with this checking for you to try if want.

Regards
Ley Foon