linux-kernel - Re: [PATCH v3 08/15] ASoC: tegra: Add audio mclk control through clk_out

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Date:   Mon, 9 Dec 2019 23:06:40 +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 08/15] ASoC: tegra: Add audio mclk control through
 clk_out_1 and extern1

07.12.2019 22:20, Sowjanya Komatineni пишет:
> 
> On 12/7/19 6:58 AM, Dmitry Osipenko wrote:
>> 06.12.2019 05:48, Sowjanya Komatineni пишет:
>>> Current ASoC driver uses extern1 as cdev1 clock from Tegra30 onwards
>>> through device tree.
>>>
>>> Actual audio mclk is clk_out_1 and to use PLLA for mclk rate control,
>>> need to clk_out_1_mux parent to extern1 and extern1 parent to PLLA_OUT0.
>>>
>>> Currently Tegra clock driver init sets the parents and enables both
>>> clk_out_1 and extern1 clocks. But these clocks parent and enables should
>>> be controlled by ASoC driver.
>>>
>>> Clock parents can be specified in device tree using assigned-clocks
>>> and assigned-clock-parents.
>>>
>>> To enable audio mclk, both clk_out_1 and extern1 clocks need to be
>>> enabled.
>>>
>>> This patch configures parents for clk_out_1 and extern1 clocks if device
>>> tree does not specify clock parents inorder to support old device tree
>>> and controls mclk using both clk_out_1 and extern1 clocks.
>>>
>>> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
>>> ---
>>>   sound/soc/tegra/tegra_asoc_utils.c | 66
>>> ++++++++++++++++++++++++++++++++++++++
>>>   sound/soc/tegra/tegra_asoc_utils.h |  1 +
>>>   2 files changed, 67 insertions(+)
>>>
>>> diff --git a/sound/soc/tegra/tegra_asoc_utils.c
>>> b/sound/soc/tegra/tegra_asoc_utils.c
>>> index 536a578e9512..8e3a3740df7c 100644
>>> --- a/sound/soc/tegra/tegra_asoc_utils.c
>>> +++ b/sound/soc/tegra/tegra_asoc_utils.c
>>> @@ -60,6 +60,7 @@ int tegra_asoc_utils_set_rate(struct
>>> tegra_asoc_utils_data *data, int srate,
>>>       data->set_mclk = 0;
>>>         clk_disable_unprepare(data->clk_cdev1);
>>> +    clk_disable_unprepare(data->clk_extern1);
>>>       clk_disable_unprepare(data->clk_pll_a_out0);
>>>       clk_disable_unprepare(data->clk_pll_a);
>>>   @@ -89,6 +90,14 @@ int tegra_asoc_utils_set_rate(struct
>>> tegra_asoc_utils_data *data, int srate,
>>>           return err;
>>>       }
>>>   +    if (!IS_ERR_OR_NULL(data->clk_extern1)) {
>>> +        err = clk_prepare_enable(data->clk_extern1);
>>> +        if (err) {
>>> +            dev_err(data->dev, "Can't enable extern1: %d\n", err);
>>> +            return err;
>>> +        }
>>> +    }
>>> +
>>>       err = clk_prepare_enable(data->clk_cdev1);
>>>       if (err) {
>>>           dev_err(data->dev, "Can't enable cdev1: %d\n", err);
>>> @@ -109,6 +118,7 @@ int tegra_asoc_utils_set_ac97_rate(struct
>>> tegra_asoc_utils_data *data)
>>>       int err;
>>>         clk_disable_unprepare(data->clk_cdev1);
>>> +    clk_disable_unprepare(data->clk_extern1);
>>>       clk_disable_unprepare(data->clk_pll_a_out0);
>>>       clk_disable_unprepare(data->clk_pll_a);
>>>   @@ -142,6 +152,14 @@ int tegra_asoc_utils_set_ac97_rate(struct
>>> tegra_asoc_utils_data *data)
>>>           return err;
>>>       }
>>>   +    if (!IS_ERR_OR_NULL(data->clk_extern1)) {
>>> +        err = clk_prepare_enable(data->clk_extern1);
>>> +        if (err) {
>>> +            dev_err(data->dev, "Can't enable extern1: %d\n", err);
>>> +            return err;
>>> +        }
>>> +    }
>> Why this is needed given that clk_extern1 is either a child of MCLK or
>> MCLK itself (on T20)? The child clocks are enabled when the parent is
>> enabled.
> 
> For T30 and later, clk_extern1 is one of the source for clk_out_1_mux.
> clk_extern1 is in CAR and it has its own gate and mux.
> 
> As audio mclk related clocks (clk_out_1, clk_out_1_mux, and extern1) are
> moved into ASoC driver from clock driver
> 
> need to enable extern1 gate as well along with clk_out1 for T30 through
> T210.
> 
> Just FYI, extern1 enable here happens only when data->clk_extern1 is
> available which is for T30 onwards.

clk_out_1 is the parent of extern1, thus extern1 is enabled by the clk
core whenever clk_out_1 is enabled because data->clk_cdev1=clk_out_1. An
I missing something?

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