[U-Boot] [PATCH 3/9] sunxi: Stop differentiating between 512M and 1G variants of the same board

[Ian Campbell <ijc@hellion.org.uk>]

On Mon, 2015-01-19 at 15:35 +0100, Hans de Goede wrote:
> Siarhei, thanks for bringing this topic up once again, I agree that this
> is ideally something which we should fix. The problem is that the only
> way to know that any new settings which we do are actually good, is to
> test them on lots of boards, and I do not mean one of each board, but
> at least 10 of each board or some such.

I agree. Having settings which are optimal for Hans' board but untested
elsewhere would not be a good idea IMHO.

> Still I would like to get this sorted, so I would like to move to the
> recommended timings for the generic JEDEC speed bins, you rightfully
> point out that those may not be 100% optimal, but given that we're
> dealing with a lot of cheap boards, I think that those are our best bet.

Agreed. In the absence of an ability to test lots of boards this is
probably the best we can do.

An alternative would be to use the settings from the factory firmware,
but I don't think we have any real reason to think these will be any
better in general than the JEDEC timings, at least not without lots of
testing (see previous paragraph).

> The plan would be for you to submit a patch for that, and then I'll add
> that to my sunxi-wip branch right away, this way all the testing I do,
> as well as all the testing people using my sunxi-wip branch do will use
> the new timings, and then once v2015.04 stabilizes a bit we can add
> that patch to u-boot-sunxi/next, getting it ready for v2015.07 .
> 
> Does that sound like a plan ?
> 
> Ian, what do you think about this ?

Go for it.

> This way we will not grow the spl, and keep an easy editable set of
> dram_para in the spl for people who like to hexedit the spl ...

At the start of the #ifdef chain you could add

#ifdef CONFIG...CUSTOM_DRAM_SETTINGS
static struct dram_para dram_para = {
    CONFIG_...CUSTOM_DRAM_SETTINGS
};
#elif ...

along with a corresponding Kconfig entry (perhaps depends on EXPERT?).

Then people who really want to tweak things could enter
"CONFIG....=.clock=XXX,.type=YYY,.." in their .config (menuconfig etc)
or defconfig to their heart's content. (only question is what the
character limit on a config option is...)

Ian.