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Subject: Re: [PATCH v3 03/15] soc: tegra: Add Tegra PMC clock registrations
 into PMC driver
To:     Sowjanya Komatineni <skomatineni@nvidia.com>,
        thierry.reding@gmail.com, jonathanh@nvidia.com,
        mperttunen@nvidia.com, gregkh@linuxfoundation.org,
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From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <5a5cfa74-66be-5c7a-04eb-88c355851c59@gmail.com>
Date:   Tue, 10 Dec 2019 21:30:00 +0300
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10.12.2019 20:48, Sowjanya Komatineni пишет:
> 
> On 12/10/19 9:41 AM, Dmitry Osipenko wrote:
>> 09.12.2019 23:46, Sowjanya Komatineni пишет:
>>> 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.
>>>>>>
>>>> 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
>> Are you sure that EXTPERIPH has a reset? What will it reset? Why it's
>> not documented in TRM?
> Yes, Extperiph1/2/3 has RST part of CAR RST_DEVICES_V bits 24/25/26

Are these bits not documented in a public TRMs? I checked
T30/114/124/210 TRMs and CLK_RST_CONTROLLER_RST_DEVICES_V_0 doesn't have
those bits in the docs.

>>> 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.
>> Could you please clarify what are "these" pins? Perhaps you meant the
>> EXTERN pin of PMC?
> By CLK1/2/3 pins, I am referring to CLK_OUT_1/2/3 pins from Tegra

I see now what you meant, thanks.

[snip}