[U-Boot] am33xx config_ddr api change needed to support mDDR

[Tom Rini]

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On 02/05/2013 03:48 AM, Markus Brunner wrote:
> Hi, for mDDR to work mddr_sel (bit 28) of ddrctrl->ddrioctrl has to
> be set. There is no way of telling config_ddr(unsigned int pll,
> unsigned int ioctrl, ...) my desired value, it won't be set atm.
> 
> From the 1.3kB ddr_ctrl struct only 2 registers are defined, which
> is fine if it's used memory mapped, however it makes it  unsuitable
> for passing values in the SPL. So at first glance I would extend 
> config_ddr() with an additional register value, because guessing
> the ddr type from the values of the other parameters is, in
> addition to being hackish, not guaranteed to work with every weired
> ram configuration. However might it be possible, that the second
> value of config_ddr() should not hold the value for
> config_io_ctrl(), but the value of my desired ddrctrl->ddrioctrl? 
> The wiki [1] from TI says that the first should _always_ be 0x18B, 
> whereas the second needs to be set depending on the mem type. We
> are talking about a set of registers named DDR_*_IOCTRL and a 
> single register called DDR_IO_CTRL, so easy to mix up.
> 
> Ragards, Markus
> 
> [1]
> http://processors.wiki.ti.com/index.php/AM335x_EMIF_Configuration_tips

Hadn't
> 
seen that wiki page before, thanks.  So a problem right now is
that yes, I hadn't seen "in the wild" anything but DDR2 or DDR3
designs.  I'm going to assume that on your custom hardware you are not
doing the EEPROM-based board detection method that the TI boards do.
We should try and lay things out so that boards where we can run-time
say "we are on board X (rev Y) and must have ..." can all out the same
functions for boards where we simply have to set that at build time
(until we get to the some-day of using a device tree or something like
that perhaps).

- -- 
Tom
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