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

[Siarhei Siamashka]

On Thu, 16 Oct 2014 10:48:34 +0200
Hans de Goede <hdegoede at redhat.com> wrote:

> Hi,
> 
> On 10/15/2014 12:34 PM, Siarhei Siamashka wrote:
> > On Wed, 15 Oct 2014 12:12:11 +0200
> > Hans de Goede <hdegoede at 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@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.

The future is happening right now ;-)

Luc has implemented the HDMI support in u-boot and ensured that it
works with the simplefb driver, providing framebuffer in the mainline
kernel. This has code has been available for several months for any
geeks, willing to fish out and cherry pick the patches. But right now
this needs to be more easily available for the users and developers.

The mainline kernel got all the basic essentials and has been ready
for the graphics and multimedia since around version 3.16

As anyone can see, the sunxi-3.4 kernel provides a rather rotten
foundation. And even though we have a reasonably good support for
both proprietary and free reverse engineered drivers with sunxi-3.4,
it still makes a lot of sense to get the graphics drivers in the
mainline kernel ASAP.

> 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.

You are the boss. We are all free to have our own private branches
anyway.

-- 
Best regards,
Siarhei Siamashka