Re: delay in the IMXCFG file

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

On Thu, Aug 20, 2015 at 03:20:54PM +0300, Igor Plyatov wrote:
> Dear Sascha,
> 
> >Hi Igor,
> >
> >On Wed, Aug 19, 2015 at 11:48:41AM +0300, Igor Plyatov wrote:
> >>Dear all,
> >>
> >>for debugging purposes I need to add some delays into the <BOARD
> >>NAME>.imxcfg file, but does not know which format it is. It looks
> >>like some kind of C, but it is confusing.
> >>
> >>Where is defined "wm 32", "soc", "dcdofs", "loadaddr" command and others?
> >They are interpreted in the imx-image tool, see scripts/imx/README and
> >scripts/imx/imx-image.c. The imx-image tool converts the commands into a
> >dcd table which is understood by the Freescale i.MX ROM Code. The ROM
> >code does not provide a delay command, so what you are looking for does
> >not exist. All the is is a nop command. This is currently not
> >implemented in imx-image, you would have to add it.
> >
> >>Which commands I can use in the IMXCFG file to create very early
> >>delay, before initialization of DRAM?
> >As said, there is nop. Otherwise there is a 'check' command to poll for
> >setting/clearing bits.
> >See the i.MX reference manual in the "Device Configuration Data (DCD)"
> >section for further information.
> 
> Thank you for explanation above!
> 
> Everywhere I see references to DCD in the Reference Manual, but I
> can not find details about DCD in the MCIMX51RM.pdf Rev. 1 2/2010.

On i.MX51 the DCD data is indeed much simpler, there are no 'check' or
'nop' commands. Instead the only command is 'wm' for write memory. You
can only choose the access width. The additional commands I mentioned
only exist on i.MX53 and newer. I just realized that most of the system
boot description is missing in the i.MX51 Reference Manual and wonder
how I ever managed to boot this successfully. Have a look in the i.MX35
Reference Manual, the DCD layout is described there. It should be
identical on i.MX51.

> 
> If you know, please give me a link to document where DCD explained
> in details, because any attempt to setup GPIO output, fails. Device
> just does not boot at all.
> 
> wm 32 0x73f88000 0x689c0319 /* hangup line in flash-header.imxcfg */

Not all modules can be accessed with DCD data. Information again is
missing in the i.MX51 Manual, but the i.MX35 Manual has "Table 7-11. DCD
Valid Modules". GPIO is missing in this table, so you can't access it
with DCD data. It's probably the same on i.MX51.

Sascha

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