Re: [PATCH] pbl updates

[Sascha Hauer <s.hauer@pengutronix.de>]

On Tue, Oct 02, 2012 at 08:36:41PM +0200, Jean-Christophe PLAGNIOL-VILLARD wrote:
> On 18:50 Tue 02 Oct     , Sascha Hauer wrote:
> > On Tue, Oct 02, 2012 at 04:30:11PM +0200, Jean-Christophe PLAGNIOL-VILLARD wrote:
> > > On 15:06 Tue 02 Oct     , Sascha Hauer wrote:
> > > > Here are two updates for the MMU code in the decompressor. The first
> > > > one may come in handy when a JTAG debugger is connected. The second
> > > > one is more important. It actually makes turning on the MMU in the
> > > > decompressor useful by making map_cachable work. It turned out that
> > > > this didn't work leaving the whole mapping uncached.
> > > > Note that the code in current master should work, but slow. Since
> > > > it actually does work I do not want to put this into the upcoming
> > > > release.
> > > As I report the current code does not work on at91sam9g45
> > > I suspect as we boot from the second ram controler on this SoC
> > > 
> > > So please hold the release that I can try those patch on sam9g45 if they fix
> > > the PBL they will be mandatory for it
> > 
> > I think they won't fix it. map_cachable currently is a noop, but this
> > should be fine as now we have a complete 1:1 uncached mapping. I don't
> > see why this shouldn't work. I hope you find out.
> > 
> > What we can do for now is to add an additional Kconfig option to make
> > enabling the MMU in the pbl optional. Then at least it should work on
> > your boards.
> Was thinking about this too

Ok, I'll prepare a patch.

> > 
> > BTW I hunted down a strange problem with the MMU on a KaRO Tx53 board.
> > It turned out that the image header (which basically is a poke table
> > to initialize the SDRAM) indeed initialized the SDRAM. The problem was
> > that this SDRAM setup depends on some other lowlevel setup which is done
> > later. The SDRAM setup was good enough to load with MMU disabled, but
> > once the MMU is enabled the SDRAM does burst accesses and the board goes
> > to nirvana.
> > Maybe your problem is related somehow.
> yeah It may solve my issue with the MMU and nand boot
> 
> I was thinking to add a initcall support to the pbl and enable the MMU at the
> right momment. This will allow to simplify the adding of generic SPL framework

I don't think this is a good idea. I don't want to grow a second
bootloader in the pbl. It should stay simple.

Sascha

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