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

[Markus Brunner]

Hi Tom,
I'm not using an eeprom, but I can't see how this would change
anything. The problem is, that the generic config_ddr from
am3xx/emif4.c isn't capable of configuring mDDR and all that's needed
is setting an additional register.
I will post a patch.

Regards,
Markus

On Wed, Feb 6, 2013 at 5:47 PM, Tom Rini <trini at ti.com> wrote:
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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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