[U-Boot] [PATCH] Revert "sunxi: dram: Use divisor P=1 for PLL5"

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 10/15/2014 12:34 PM, Siarhei Siamashka wrote:
> On Wed, 15 Oct 2014 12:12:11 +0200
> Hans de Goede <hdegoede@redhat.com> wrote:
> 
>> This change breaks various hardcoded assumptions in the linux-sunxi-3.4
>> kernels, causing a divide by 0 error in the linux-sunxi-3.4 nand driver,
>> rendering 3.4 kernels unbootable. Besides this problem, it also breaks LCD
>> output (on devices without nand).
>>
>> Fixes for these issues are being added to the linux-sunxi-3.4 kernel, but for
>> now it seems better to revert this.
>>
>> This reverts commit 013f2d746955147439215a4939655c9ed6bdd866.
> 
> As mentioned in the commit message
>     https://www.mail-archive.com/linux-sunxi at googlegroups.com/msg07884.html
> the hardcoded assumptions in the sunxi-3.4 kernel are still bad
> with or without this revert if somebody tries to use higher DRAM
> clock speeds.
> 
> The patch in question just smokes out bugs, which are otherwise still
> there.
> 
> Going forward, the mainline kernel needs the G2D driver and it needs
> to run at a decent clock speed to be provide reasonable performance.
> Low PLL5P clock speed is limiting our options.
> 
> This revert does not do anyone any favour and only postpones the
> resolution of the problem.

I agree that we need to fix the linux-sunxi-3.4 kernels to work properly with
different pll5 settings, which is why I've actually send a fix for some pll5
issues to the linux-sunxi list and acked your patches which fix other bits.

I can understand you want to have optimal settings for the G2D stuff, and I'm
not against that. But getting the G2D stuff upstream is something which
is still far in the future. I really want people to be able to start using
upstream u-boot, starting today. And it will take some time for the sunxi-3.4
fixes to trickle down to users.

So for now I believe we really should revert the PLL5 u-boot changes as they
break some kernels from booting.

Then once getting G2D support upstream really comes into the picture
(e.g. upstream kernel patches are posted and being reviewed), then we can talk
about re-applying the PLL5 changes, but for now I believe that reverting them
is best.

Regards,

Hans