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Subject: Re: [PATCH v3 03/15] soc: tegra: Add Tegra PMC clock registrations
 into PMC driver
From:   Dmitry Osipenko <digetx@gmail.com>
To:     Sowjanya Komatineni <skomatineni@nvidia.com>,
        thierry.reding@gmail.com, jonathanh@nvidia.com,
        mperttunen@nvidia.com, gregkh@linuxfoundation.org,
        sboyd@kernel.org, tglx@linutronix.de, robh+dt@kernel.org,
        mark.rutland@arm.com
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        mturquette@baylibre.com, horms+renesas@verge.net.au,
        Jisheng.Zhang@synaptics.com, krzk@kernel.org, arnd@arndb.de,
        spujar@nvidia.com, josephl@nvidia.com, vidyas@nvidia.com,
        daniel.lezcano@linaro.org, mmaddireddy@nvidia.com,
        markz@nvidia.com, devicetree@vger.kernel.org,
        linux-clk@vger.kernel.org, linux-tegra@vger.kernel.org,
        linux-kernel@vger.kernel.org, lgirdwood@gmail.com,
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Date:   Sat, 7 Dec 2019 18:53:34 +0300
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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?

4. clk_m_div2/4 are internal PMC OSC dividers and thus these clocks
should belong to PMC.