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 15:05:10 -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 08/15] ASoC: tegra: Add audio mclk control through
 clk_out_1 and extern1


On 12/9/19 12:06 PM, Dmitry Osipenko wrote:
> 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?
>
> [snip]
extern1 is the parent for clk_out_1. explained extern1 clock path to 
clk_out in reply to your comment in other patch of this series.