Re: [PATCH v3 03/15] soc: tegra: Add Tegra PMC clock registrations into PMC driver

[Sowjanya Komatineni <skomatineni@nvidia.com>]

On 12/10/19 9:41 AM, Dmitry Osipenko wrote:
> 10.12.2019 19:53, Sowjanya Komatineni пишет:
>> On 12/9/19 3:03 PM, Sowjanya Komatineni wrote:
>>> On 12/9/19 12:46 PM, Sowjanya Komatineni wrote:
>>>> On 12/9/19 12:12 PM, Dmitry Osipenko wrote:
>>>>> 08.12.2019 00:36, Sowjanya Komatineni пишет:
>>>>>> On 12/7/19 11:59 AM, Sowjanya Komatineni wrote:
>>>>>>> On 12/7/19 8:00 AM, Dmitry Osipenko wrote:
>>>>>>>> 07.12.2019 18:53, Dmitry Osipenko пишет:
>>>>>>>>> 07.12.2019 18:47, Dmitry Osipenko пишет:
>>>>>>>>>> 07.12.2019 17:28, Dmitry Osipenko пишет:
>>>>>>>>>>> 06.12.2019 05:48, Sowjanya Komatineni пишет:
>>>>>>>>>>>> Tegra210 and prior Tegra PMC has clk_out_1, clk_out_2, clk_out_3
>>>>>>>>>>>> with
>>>>>>>>>>>> mux and gate for each of these clocks.
>>>>>>>>>>>>
>>>>>>>>>>>> Currently these PMC clocks are registered by Tegra clock driver
>>>>>>>>>>>> using
>>>>>>>>>>>> clk_register_mux and clk_register_gate by passing PMC base
>>>>>>>>>>>> address
>>>>>>>>>>>> and register offsets and PMC programming for these clocks
>>>>>>>>>>>> happens
>>>>>>>>>>>> through direct PMC access by the clock driver.
>>>>>>>>>>>>
>>>>>>>>>>>> With this, when PMC is in secure mode any direct PMC access
>>>>>>>>>>>> from the
>>>>>>>>>>>> non-secure world does not go through and these clocks will
>>>>>>>>>>>> not be
>>>>>>>>>>>> functional.
>>>>>>>>>>>>
>>>>>>>>>>>> This patch adds these clocks registration with PMC as a clock
>>>>>>>>>>>> provider
>>>>>>>>>>>> for these clocks. clk_ops callback implementations for these
>>>>>>>>>>>> clocks
>>>>>>>>>>>> uses tegra_pmc_readl and tegra_pmc_writel which supports PMC
>>>>>>>>>>>> programming
>>>>>>>>>>>> in secure mode and non-secure mode.
>>>>>>>>>>>>
>>>>>>>>>>>> Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
>>>>>>>>>>>> ---
>>>>>>>>>> [snip]
>>>>>>>>>>
>>>>>>>>>>>> +
>>>>>>>>>>>> +static const struct clk_ops pmc_clk_gate_ops = {
>>>>>>>>>>>> +    .is_enabled = pmc_clk_is_enabled,
>>>>>>>>>>>> +    .enable = pmc_clk_enable,
>>>>>>>>>>>> +    .disable = pmc_clk_disable,
>>>>>>>>>>>> +};
>>>>>>>>>>> What's the benefit of separating GATE from the MUX?
>>>>>>>>>>>
>>>>>>>>>>> I think it could be a single clock.
>>>>>>>>>> According to TRM:
>>>>>>>>>>
>>>>>>>>>> 1. GATE and MUX are separate entities.
>>>>>>>>>>
>>>>>>>>>> 2. GATE is the parent of MUX (see PMC's CLK_OUT paths diagram
>>>>>>>>>> in TRM).
>>>>>>>>>>
>>>>>>>>>> 3. PMC doesn't gate EXTPERIPH clock but could "force-enable" it,
>>>>>>>>>> correct?
>>>>>> Was following existing clk-tegra-pmc as I am not sure of reason for
>>>>>> having these clocks registered as separate mux and gate clocks.
>>>>>>
>>>>>> Yes, PMC clocks can be registered as single clock and can use clk_ops
>>>>>> for set/get parent and enable/disable.
>>>>>>
>>>>>> enable/disable of PMC clocks is for force-enable to force the clock to
>>>>>> run regardless of ACCEPT_REQ or INVERT_REQ.
>>>>>>
>>>>>>>>> 4. clk_m_div2/4 are internal PMC OSC dividers and thus these clocks
>>>>>>>>> should belong to PMC.
>>>>>>>> Also, it should be "osc" and not "clk_m".
>>>>>>> I followed the same parents as it were in existing clk-tegra-pmc
>>>>>>> driver.
>>>>>>>
>>>>>>> Yeah they are wrong and they should be from osc and not clk_m.
>>>>>>>
>>>>>>> Will fix in next version.
>>>>>>>
>>> Reg clk_m_div2/3, they are dividers at OSC pad and not really internal
>>> to PMC block.
>>>
>>> current clock driver creates clk_m_div clocks which should actually be
>>> osc_div2/osc_div4 clocks with osc as parent.
>>>
>>> There are no clk_m_div2 and clk_m_div4 from clk_m
>>>
>>> Will fix this in next version.
>>>
>>>>> Could you please describe the full EXTPERIPH clock topology and how the
>>>>> pinmux configuration is related to it all?
>>>>>
>>>>> What is internal to the Tegra chip and what are the external outputs?
>>>>>
>>>>> Is it possible to bypass PMC on T30+ for the EXTPERIPH clocks?
>>>> PMC CLK1/2/3 possible sources are OSC_DIV1, OSC_DIV2, OSC_DIV4,
>>>> EXTPERIPH from CAR.
>>>>
>>>> OSC_DIV1/2/4 are with internal dividers at the OSC Pads
>>>>
>>>> EXTPERIPH is from CAR and it has reset and enable controls along with
>>>> clock source selections to choose one of the PLLA_OUT0, CLK_S,
>>>> PLLP_OUT0, CLK_M, PLLE_OUT0
>>>>
>>>> So, PMC CLK1/2/4 possible parents are OSC_DIV1, OSC_DIV2, OSC_DIV4,
>>>> EXTERN.
>>>>
>>>>
>>>> CLK1/2/3 also has Pinmux to route EXTPERIPH output on to these pins.
>>>>
>>>>
>>>> When EXTERN output clock is selected for these PMC clocks thru
>>>> CLKx_SRC_SEL, output clock is from driver by EXTPERIPH from CAR via
>>>> Pinmux logic or driven as per CLKx_SRC_SEL bypassing pinmux based on
>>>> CLKx_ACCEPT_REQ bit.
>>>>
>>>>
>>>> PMC Clock control register has bit CLKx_ACCEPT_REQ
>>>> When CLKx_ACCEPT_REQ = 0, output clock driver is from by EXTPERIPH
>>>> through the pinmux
>>>> When CLKx_ACCEPT_REQ = 1, output clock is based on CLKx_SRC_SEL bits
>>>> (OSC_DIV1/2/4 and EXTPERIPH clock bypassing the pinmux)
>>>>
>>>> FORCE_EN bit in PMC CLock control register forces the clock to run
>>>> regardless of this.
>> PMC clock gate is based on the state of CLKx_ACCEPT_REQ and FORCE_EN
>> like explained above.
>>
>> CLKx_ACCEPT_REQ is 0 default and FORCE_EN acts as gate to enable/disable
>> EXTPERIPH clock output to PMC CLK_OUT_1/2/3.
> [and to enable OSC as well]
>
>> So I believe we need to register as MUX and Gate rather than as a single
>> clock. Please confirm.
> 1. The force-enabling is applied to both OSC and EXTERN sources of
> PMC_CLK_OUT_x by PMC at once.
>
> 2. Both of PMC's force-enabling and OSC/EXTERN selection is internal to PMC.
>
> Should be better to define it as a single "pmc_clk_out_x". I don't see
> any good reasons for differentiating PMC's Gate from the MUX, it's a
> single hardware unit from a point of view of the rest of the system.
>
> Peter, do you have any objections?

We added fallback option for audio mclk and also added check for 
assigned-clock-parents dt property in audio driver and if its not then 
we do parent init configuration in audio driver.

Current clock driver creates 2 separate clocks clk_out_1_mux and 
clk_out_1 for each pmc clock in clock driver and uses extern1 as parent 
to clk_out_1_mux and clk_out_1_mux is parent to clk_out_1.

With change of registering each pmc clock as a single clock, when we do 
parent init assignment in audio driver when assigned-clock-properties 
are not used in DT (as we removed parent inits for extern and clk_outs 
from clock driver), we should still try to get clock based on 
clk_out_1_mux as parent assignment of extern1 is for clk_out_1_mux as 
per existing clock tree.

clk_out_1_mux clock retrieve will fail with this change of single clock 
when any new platform device tree doesn't specify assigned-clock-parents 
properties and tegra_asoc_utils_init fails.

With single clock, extern1 is the parent for clk_out_1 and with separate 
clocks for mux and gate, extern1 is the parent for clk_out_1_mux.