Hi Sean,
On 5/11/22 18:48, Sean Anderson wrote:
On 5/10/22 5:51 AM, Amelie Delaunay wrote:
Hi Patrick, Hi Sean,
On 5/9/22 16:37, Patrick DELAUNAY wrote:
Hi Sean,
On 5/8/22 20:21, Sean Anderson wrote:
On 4/26/22 8:37 AM, Patrick Delaunay wrote:
Add the counter of the PLL user n_pll_cons managed by the 2 functions stm32_usbphyc_pll_enable / stm32_usbphyc_pll_disable.
This counter allow to remove the function stm32_usbphyc_is_init and it is a preliminary step for ck_usbo_48m introduction.
Is it necessary to disable this clock before booting to Linux? If it isn't, then perhaps it is simpler to just not disable the clock.
--Sean
No, it is not necessary, we only need to enable the clock for the first user.
I copy the clock behavior from kernel,
but I agree that can be simpler.
Amelie any notice about this point ?
Do you prefer that I kept the behavior - same as kernel driver - or I simplify the U-Boot driver ?
In case the PLL has not been disabled before Kernel boot, usbphyc Kernel driver will wait for the PLL pwerdown. USB could also not being used in Kernel, so PLL would remain enabled, and would waste power. I am rather in favor of disabling the PLL.
It should be disabled if clk_ignore_unused is not in the kernel parameters, as long as Linux is also aware of the clock.
Generally, I would like to avoid refcounting if possible. Many U-Boot drivers do not disable their clocks (because they don't do any cleanup), so you can end up with the clock staying on anyway.
--Sean
Regards, Amelie
Patrick
In general, I'm also in favor of not disabling the clock in U-Boot.
But this PLL with vdda1v1 and vdda1v8 dependency is requested for
- USBPHYC himself or
- source clock of RCC,
And we have have see many issue for this PLL initialization sequence / dependencies.
So for clock support, I only reused the existing/working function called by the PHY ops init & exit =
stm32_usbphyc_phy_init & stm32_usbphyc_phy_exit
=> the PLL and the associated VDDÂ are already deactivated on USBPHYC exit.
And to be coherent I for the same for the clock to avoid conflict between these 2 users
(USBPHYC or RCC) as it is done also in Linux kernel.
Avoid to deactivate PLL on clock disable is a major objection or just a advice?
Regards
Patrick
.