Re: [PATCH v2 3/3] clk: Drop the rate range on clk_put

[Maxime Ripard <maxime@cerno.tech>]

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Hi Marek,

On Wed, Mar 30, 2022 at 10:06:13AM +0200, Marek Szyprowski wrote:
> On 25.03.2022 17:11, Maxime Ripard wrote:
> > While the current code will trigger a new clk_set_rate call whenever the
> > rate boundaries are changed through clk_set_rate_range, this doesn't
> > occur when clk_put() is called.
> >
> > However, this is essentially equivalent since, after clk_put()
> > completes, those boundaries won't be enforced anymore.
> >
> > Let's add a call to clk_set_rate_range in clk_put to make sure those
> > rate boundaries are dropped and the clock drivers can react.
> >
> > Let's also add a few tests to make sure this case is covered.
> >
> > Fixes: c80ac50cbb37 ("clk: Always set the rate on clk_set_range_rate")
> > Signed-off-by: Maxime Ripard <maxime@cerno.tech>
> 
> This patch landed recently in linux-next 20220328 as commit 7dabfa2bc480 
> ("clk: Drop the rate range on clk_put()"). Sadly it breaks booting of 
> the few of my test systems: Samsung ARM 32bit Exynos3250 based Rinato 
> board and all Amlogic Meson G12B/SM1 based boards (Odroid C4, N2, Khadas 
> VIM3/VIM3l). Rinato hangs always with the following oops:
> 
> --->8---
> 
> Kernel panic - not syncing: MCT hangs after writing 4 (offset:0x420)
> CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.17.0-rc1-00014-g7dabfa2bc480 
> #11551
> Hardware name: Samsung Exynos (Flattened Device Tree)
>   unwind_backtrace from show_stack+0x10/0x14
>   show_stack from dump_stack_lvl+0x58/0x70
>   dump_stack_lvl from panic+0x10c/0x328
>   panic from exynos4_mct_tick_stop+0x0/0x2c
> ---[ end Kernel panic - not syncing: MCT hangs after writing 4 
> (offset:0x420) ]---
> 
> --->8---
> 
> Amlogic boards hang randomly during early userspace init, usually just 
> after loading the driver modules.
> 
> Reverting $subject on top of linux-next fixes all those problems.
> 
> I will try to analyze it a bit more and if possible provide some more 
> useful/meaning full logs later.

I'm not sure what could go wrong there, but if you can figure out the
clock, if it tries to set a new rate and what rate it is, it would be
awesome :)

Maxime

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