Re: [PATCH 1/6] ARM: add common definitions for i.MX50 SOC

From: Jason Cooper <jason@lakedaemon.net>
To: Sascha Hauer <s.hauer@pengutronix.de>
Cc: barebox@lists.infradead.org, Alexander Kurz <akurz@blala.de>
Subject: Re: [PATCH 1/6] ARM: add common definitions for i.MX50 SOC
Date: Tue, 13 Sep 2016 13:04:05 +0000	[thread overview]
Message-ID: <20160913130405.GK12916@io.lakedaemon.net> (raw)
In-Reply-To: <20160913070604.qehrkh6gxrux5icg@pengutronix.de>

Hi Sascha, Alexander,

On Tue, Sep 13, 2016 at 09:06:04AM +0200, Sascha Hauer wrote:
> On Mon, Sep 12, 2016 at 10:17:18AM +0200, Alexander Kurz wrote:
> > On Mon, 12 Sep 2016, Sascha Hauer wrote:
> > > On Fri, Sep 09, 2016 at 05:43:39PM +0200, Alexander Kurz wrote:
> > > > Signed-off-by: Alexander Kurz <akurz@blala.de>
> > > > ---
> > > >  Documentation/boards/imx.rst                   |  1 +
> > > >  arch/arm/mach-imx/include/mach/generic.h       | 13 +++++++++++++
> > > >  arch/arm/mach-imx/include/mach/imx_cpu_types.h |  1 +
> > > >  3 files changed, 15 insertions(+)
> > > 
> > > Seems to be straight forward to add i.MX50 support. I have nothing to
> > > add, except: Applied, thanks
> > > 
> > > Out of curiosity: What device do you use with i.MX50? Is it some E-Book
> > > reader again?
> > The imx50 has a build-in e-ink driver, so it is more or less a SOC 
> > tailored on e-books. It is used in some already outdated e-books like the
> > 4th and 5th generation Kindles, some Kobos and Tolinos.
> > The successor for the imx50 became the e-ink driver equiped variants 
> > of the imx6sl, which is used in most current generation e-book readers.
> > 
> > While the current patchsets will enable barebox to run on different
> > e-books e.g. when beeing booted via an installed bootloader, there is 
> > still an open issue: RAM initialization.
> > Freescale used a "DRAMMC" which seems to be very unique to this SOC.
> > Documentation on it is available in the Reference Manual, but it covers
> > some details quite briefly.
> > Related on barebox:
> > it is not clear, whether DRAMMC initialization via imximg-DCD is possible
> > at all. All existing bootloaders I have seen so far used some 
> > imximg-plugin code (which is currently not supported by barebox).
> > A two-stage bootloader implementation via xload may be an alternative.
> 
> Yes, that could work. How I understand it the plugin image is
> responsible for initializing SDRAM and for loading the final image.
> Then the job of the ROM is done anyway, so normally I do not see a
> reason for plugin images. The only usecase seems to be HAB when the
> final image is checked by the HAB code when returning to ROM.

So, I found my Sandisk Connect WMD (Wireless Media Drive) and I also
re-located the open source dump by Sandisk [1].

The first problem I need to solve is the DDR training code.  The device
shipped with U-boot, and the training code seems to be in flash_header.S
[2].  There's a large number of lines preceded by comments of the form

  /* setmem /32 0x140000f8 = 0x00010101 */

which lends itself to a conversion into .imxcfg format.  However,
there's quite a bit of code that doesn't appear to be doing simple
writes.  Additionally, there's a lowlevel_init.S in the same directory.

There is a linker script putting flash_header.o at the beginning of the
binary image.  Is it easier to just do that, bypassing imx-image?  Or,
is there a conversion utility my google fu isn't pulling up?

thx,

Jason.

[1] https://github.com/SanDisk-Open-Source/wireless-media-drive
[2] https://github.com/SanDisk-Open-Source/wireless-media-drive/blob/master/u-boot-2009.08/board/freescale/mx50_rdp/flash_header.S

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