Hi Stephen,
On ven., juil. 06 2018, Stephen Boyd sboyd@kernel.org wrote:
Quoting Gregory CLEMENT (2018-06-29 07:44:02)
Hi, On mar., juin 19 2018, Gregory CLEMENT gregory.clement@bootlin.com wrote:
Switching the CPU from the L2 or L3 frequencies (300 and 200 Mhz respectively) to L0 frequency (1.2 Ghz) requires a significant amount of time to let VDD stabilize to the appropriate voltage. This amount of time is large enough that it cannot be covered by the hardware countdown register. Due to this, the CPU might start operating at L0 before the voltage is stabilized, leading to CPU stalls.
To work around this problem, we prevent switching directly from the L2/L3 frequencies to the L0 frequency, and instead switch to the L1 frequency in-between. The sequence therefore becomes:
- First switch from L2/L3(200/300MHz) to L1(600MHZ)
- Sleep 20ms for stabling VDD voltage
- Then switch from L1(600MHZ) to L0(1200Mhz).
Do you have any comment on this fix?
Looks good. Is it crashing right now? I can throw it into clk-fixes if it's fixing pain.
Yes for the SoC capable to run at 1200Mhz it crashes. At the time the initial support was provided, my SoC version only ran at 1000MHz, so the problem was not noticed.
Thanks,
Gregory