Re: [PATCH 08/26] power: Add iMX8M block ctrl driver for dispmix

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Heiko,


> >>> Hmm.. unfortunately ... I had applied your 2 clock patches, which
> >>> fixed a problem with enabling parent clocks ... but they broke booting
> >>> on a carrier which has fec ethernet! After "Net: " output the board hang...
> >>>
> >>> I reverted your 2 clock patches and it bootet again ... so there is
> >>> a problem ... try to get some more time to look into...
> >>>  
> >>
> >> We have a fec, but we had I think two patches more on it. I forget to
> >> answer Marek
> >> about them because I don't have my board now and because he is
> >> partially right (or maybe right).
> >> Anyway when we boot we could have and we have clocks that are enabled
> >> by bootrom or SPL that
> >> we need to declare as enable like PLL2/PLL3 those clocks are parts or
> >> could be part of reparent so,
> >> you need to have a reference counter on them that allow to not disable
> >> during the down chain disable
> >> and up chain enable. I think that what happens to your ethernet it's
> >> that you disable some clock that is
> >> critical to the board to survive. I had a patch merged by Tom that  
> > 
> > Yep, thats what I think too! If you access registers in a block for
> > which the clock is not enabled ... it just hang...
> >   
> >> prints the clock name so if you enable
> >> the debug of the clock you will find that your board stops working
> >> during one of this reparinting.  
> > 
> > I currently work on 2024.07... will rebase if 2024.10 is out...
> > 
> > Ah, you mean:
> > 
> > commit a70d991212c9684e09ed80ece69ce1ff7bfd9f08
> > Author: Michael Trimarchi <michael@amarulasolutions.com>
> > Date:   Tue Jul 9 08:28:13 2024 +0200
> > 
> >      clk: clk-uclass: Print clk name in clk_enable/clk_disable
> > 
> >      Print clk name in clk_enable and clk_disable. Make sense to know
> >      what clock get disabled/enabled before a system crash or system
> >      hang.
> > 
> >      Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
> > 
> > I have the same change when I debug :-P
> > 
> > IIRC I did not see the clock names ... but I will recheck!  
> 
> I see with your patch the clock names, so fine... and see [1]
> 
> Hmm... I am on imx8mp, and I think the changes the patchset do in
> 
> "clk: imx8mn: Prevent clock critical path from disabling during reparent and set_rate"
> 
> are in clk-imx8mp already ...
> 
> Ported the patch from patchset
> 
> "[PATCH 05/26] clk: imx8mm: Mark IMX8MM_SYS_PLL2 and IMX8MM_SYS_PLL3 as enabled"
> 
> to imx8mp [2] and fec ethernet works again for me on imx8mp!
> 
> Could you add this if you post a v2 ?

TBH I don't feel like the below change is the correct one, it is too
specific. The clock core is recursive and thus should handle the
reparenting situations gracefully.

I posted a series that is targeting the LVDS output on imx8mp. You
should probably consider checking these patches as well if you work
on imx8mp as well. I also had similar breakages with Ethernet which
happened during the assigned-clocks handling. This patch, which is more
future and platform agnostic, fixed it:

https://lore.kernel.org/u-boot/20240910101344.110633-3-miquel.raynal@bootlin.com/

My series is complimentary, even though there are some overlaps that we
need to merge.

Thanks,
Miquèl