Re: [PATCH v1] clk: qcom: lpass: Add CLK_IGNORE_UNUSED for lpass clocks
From: Stephen Boyd
Date: Mon Jan 07 2019 - 16:04:41 EST
Quoting Taniya Das (2019-01-06 22:26:00)
> Hello Stephen,
> On 12/21/2018 2:34 AM, Stephen Boyd wrote:
> > Quoting Taniya Das (2018-12-20 03:46:25)
> >> The LPASS clocks has a dependency on the GCC lpass clocks to be enabled
> >> before accessing them and that was the reason to mark the gcc lpass clocks
> >> as critical. But in the case where the lpass subsystem would require a
> >> restart, toggling the lpass reset would from HW clear the SW enable bits
> >> of the GCC lpass clocks. Thus the next time bringing up the lpass subsystem
> >> out of reset would fail.
> >> Allow the lpass clock driver to enable/disable the gcc lpass clocks and
> >> mark the lpass clocks not be accessed during late_init if no client vote.
> > You need to add more details here. It feels like you wrote the beginning
> > of a paragraph and then stopped abruptly, leaving the reader hanging for
> > the whole story. Why is late_init important? Why do we need to leave
> > them on from the bootloader? What if the bootloader doesn't leave them
> > enabled? This is all rather hacky so I'm deeply confused. Does the lpass
> > driver need to get these gcc clks and enable/prepare them during probe?
> > But then it needs to also allow a reset happen and change the clk state?
> > I suspect this situation is circling a larger problem where a reset is
> > toggled and that changes some clk state without the clk framework
> > knowing. There's not much we can do about that besides having some
> > mechanism for the clks to know that their state is now out of sync. If
> > that can be done on the provider driver side then we should have an
> > easier time not needing to write a bunch of framework code to handle
> > this. OMAP folks are dealing with the same problems from what I recall.
> Hmm, if I mark the CLK_IS_CRITICAL, I don't see a way to handle it in
> provider. Please suggest if you think provider could handle it.
As far as I know, I'm not suggesting the use of CLK_IS_CRITICAL here.
But removing CLK_IS_CRITICAL and relying on some random bootloader
behavior also looks wrong. Can you clarify what's going on?