[U-Boot] [PATCH 00/35][RFC] arm: socfpga: Usability fixes

[Marek Vasut]

On Tuesday, September 16, 2014 at 11:29:45 PM, dinguyen wrote:
> On Tue, 16 Sep 2014, Marek Vasut wrote:
> > On Tuesday, September 16, 2014 at 06:28:52 PM, Dinh Nguyen wrote:
> > > On 09/16/2014 08:18 AM, Pavel Machek wrote:
> > > > Hi!
> > > > 
> > > > On Mon 2014-09-15 13:05:53, Marek Vasut wrote:
> > > >> This entire RFC series is the first stab at making SoCFPGA usable
> > > >> with mainline U-Boot again. There are still some bits missing, but
> > > >> in general, this allows me to use mainline U-Boot on my SoCFPGA
> > > >> systems. The big missing part is the SPL generation, which still
> > > >> needs a lot of additional work.
> > > >> 
> > > >> This set contains patches for a few subsystems, bu the most part is
> > > >> the SoCFPGA chip support.
> > > >> 
> > > >> Most of the patches should be in good shape already, so I wonder if
> > > >> the RFC tag is really necessary.
> > > > 
> > > > Just... I earlier today I tested Marek's git tree based on this
> > > > series, and it works well for me on board similar to sockit.
> > > > 
> > > > So
> > > > 
> > > > Tested-by: Pavel Machek <pavel at denx.de>
> > > > 
> > > > Thanks and best regards,
> > > > 
> > > > 									
Pavel
> > > 
> > > I applied all the patches to v2014.10-rc2, and I see that the watchdog
> > > has been enabled and it's getting reset:
> > > 
> > > U-Boot 2014.10-rc2-00139-g70e9e3e (Sep 16 2014 - 11:21:38)
> > > 
> > > CPU:   Altera SoCFPGA Platform
> > > BOARD: Altera SoCFPGA Cyclone5 Board
> > > 
> > >        Watchdog enabled
> > > 
> > > DRAM:
> > > U-Boot SPL 2013.01.01-00019-g9cce15f (Jul 18 2013 - 13:05:43)
> > > SDRAM : Initializing MMR registers
> > > SDRAM : Calibrating PHY
> > > SEQ.C: Preparing to start memory calibration
> > > SEQ.C: CALIBRATION PASSED
> > > ALTERA DWMMC: 0
> > > reading u-boot.img
> > > reading u-boot.img
> > > 
> > > 
> > > U-Boot 2014.10-rc2-00139-g70e9e3e (Sep 16 2014 - 11:21:38)
> > > 
> > > CPU:   Altera SoCFPGA Platform
> > > BOARD: Altera SoCFPGA Cyclone5 Board
> > > 
> > >        Watchdog enabled
> > > 
> > > DRAM:
> > This doesn't seem like a WDT problem. How much DRAM is there on that kit
> > ? In
> 
> The devkit has 1GB.

Ah, thanks for this info!

> > any case, try this:
> > 
> > 1) Edit arch/arm/cpu/armv7/socfpga/misc.c
> > 2) Locate call to get_ram_size()
> > 3) Replace this function call with the size of your DRAM in bytes.
> > 
> >    (that is, make it "gd->ram_size = 128 * 1024 * 1024;" if you have
> >    128MiB)
> > 
> > I suspect get_ram_size() on socfpga is still broken in mainline and
> > causes this crash you observe.
> 
> Yes, tracked it down to get_ram_size(). I forced gd->ram_size to 1GB and
> it works fine for me now. I'll try to spend some cycles to debug the
> problem.

Hmmmmm, how much DRAM can the SoCFPGA chip drive in total ? 

Well, consider a theoretical SoCFPGA board with 128MiB of DRAM attached to it, 
what happens if I try to write at address of the 129th MiB (which is past the 
DRAM) ? Will this generate an DABT for the ARM core or will some kind of DRAM 
"mirroring" or "wraparound" happen such that I would write to the content of 1st 
MiB of the DRAM ?

If I would get DABT, then there is a rather easy fix for that, see 
arch/arm/cpu/arm926ejs/mxs/spl_mem_init.c and mxs_mem_get_size() function. The 
function places an assembly return instruction into the DABT handler entry 
position (offset 0x14 in ARM vector table IIRC) and then runs the 
get_dram_size() . The assembly instruction only returns from the DABT handler 
right past the code where the DABT happened. For the get_ram_size(), the read 
from the unpopulated DRAM space contains zeroes and the function doesn't even 
realize the DABT happened. But it considers the DRAM invalid and thus this works 
correctly. That's how it detects the amount of DRAM.

You might want to consider something similar if that's how it behaves on 
SoCFPGA.

> > btw you don't happen to have a spare CV and AV kits you could send me, so
> > I can do the testing rounds on them too, do you ?
> 
> I'll look around.

Thanks!