[Freedreno] [RFC PATCH 1/2] clk: qcom: implement RCG2 'parked' clock support

[Dmitry Baryshkov]

On 04/10/2023 15:52, Bryan O'Donoghue wrote:
> On 04/10/2023 13:08, Dmitry Baryshkov wrote:
>> On Wed, 4 Oct 2023 at 12:27, Bryan O'Donoghue
>> <bryan.odonoghue at linaro.org> wrote:
>>>
>>> On 04/10/2023 01:31, Dmitry Baryshkov wrote:
>>>> clk_rcg2_shared_ops implements support for the case of the RCG which
>>>> must not be completely turned off. However its design has one major
>>>> drawback: it doesn't allow us to properly implement the is_enabled
>>>> callback, which causes different kinds of misbehaviour from the CCF.
>>>>
>>>> Follow the idea behind clk_regmap_phy_mux_ops and implement the new
>>>> clk_rcg2_parked_ops. It also targets the clocks which must not be fully
>>>> switched off (and shared most of the implementation with
>>>> clk_rcg2_shared_ops). The major difference is that it requires that the
>>>> parent map doesn't conain the safe (parked) clock source. Instead if 
>>>> the
>>>> CFG_REG register points to the safe source, the clock is considered to
>>>> be disabled.
>>>
>>> Why not have a new bit in .flags ?
>>>
>>> Instead of lying about the clock being off, mark the clock as "parked",
>>> or "safe parked" or whatever term we choose for it ?
>>
>> The main problem with adding flags doesn't fully scale. From the CCF
>> perspective, what should be the difference between parked and disabled
>> clocks? How should it treat the parked one?
> 
> Exactly the same as a disabled clock, except you get a "parked" instead 
> of a "disabled" when looking up its state and you don't have to
> 
> -    { .fw_name = "bi_tcxo" },
> 
> Also you can then flag for branch2 clocks the same thing - so parking 
> would be done at a higher level in the CCF.

Without this removal there is no easy way to identify if the clock is 
parked to XO or if it is reparented to that clock.


-- 
With best wishes
Dmitry