Re: [PATCH 4/5] clk: spacemit: reject rate changes to running firmware PLLs

[Troy Mitchell]

On Thu Sep 10, 2026 at 9:31 PM +08, Yao Zi wrote:
> On Wed, Sep 09, 2026 at 10:07:04PM +0800, Troy Mitchell wrote:
>> CLK_SET_RATE_GATE only protects clocks prepared through CCF. A PLL left
>> running by firmware can have a zero prepare count, so this flag alone
>> cannot prevent set_rate() from reprogramming a live PLL.
>
> Would it be a better idea to simply turn off the PLL before reprogramming,
> since protected by CLK_SET_RATE_GATE, re-programming never happens when
> the PLL is required by downstream? This also seems to be simpler.
Then assigned-clock-rates on the PLL provider node? I tested this
on K3: .set_rate() was called during provider registration, with PLL3's
prepare count still zero while the CPUs were running on it. Disabling
PLL3 hung the board. CLK_SET_RATE_GATE therefore does not protect users
that CCF has not yet accounted for.


-- 
Troy Mitchell

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