Message-ID: <302d8483-513c-9c20-e4d4-1e24f2b317d6@nvidia.com>
Date:   Tue, 10 Dec 2019 11:18:50 -0800
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <mperttunen@...dia.com>,
        <gregkh@...uxfoundation.org>, <sboyd@...nel.org>,
        <tglx@...utronix.de>, <robh+dt@...nel.org>, <mark.rutland@....com>
CC:     <allison@...utok.net>, <pdeschrijver@...dia.com>,
        <pgaikwad@...dia.com>, <mturquette@...libre.com>,
        <horms+renesas@...ge.net.au>, <Jisheng.Zhang@...aptics.com>,
        <krzk@...nel.org>, <arnd@...db.de>, <spujar@...dia.com>,
        <josephl@...dia.com>, <vidyas@...dia.com>,
        <daniel.lezcano@...aro.org>, <mmaddireddy@...dia.com>,
        <markz@...dia.com>, <devicetree@...r.kernel.org>,
        <linux-clk@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <lgirdwood@...il.com>,
        <broonie@...nel.org>, <perex@...ex.cz>, <tiwai@...e.com>,
        <alexios.zavras@...el.com>, <alsa-devel@...a-project.org>
Subject: Re: [PATCH v3 03/15] soc: tegra: Add Tegra PMC clock registrations
 into PMC driver


On 12/10/19 10:30 AM, Dmitry Osipenko wrote:
> 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@...dia.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.
>
Yeah these bits are missing in all Tegra TRM docs. Will request for 
having EXTPERIPH reset bits to be updated in TRM...
>>>> 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}

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