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

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Message-ID: <288a1701-def6-d628-26bc-a305f817bdb1@gmail.com>
Date:   Sat, 7 Dec 2019 19:00:04 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.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

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?
> 
> 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".