Date:   Tue, 17 Dec 2019 08:12:24 -0800
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <mperttunen@...dia.com>, <sboyd@...nel.org>
CC:     <gregkh@...uxfoundation.org>, <tglx@...utronix.de>,
        <robh+dt@...nel.org>, <mark.rutland@....com>,
        <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 12/17/19 7:36 AM, Dmitry Osipenko wrote:
> 17.12.2019 04:29, Sowjanya Komatineni пишет:
>> On 12/7/19 11:20 AM, Sowjanya Komatineni wrote:
>>> 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.
>>>
>>>>>        err = clk_prepare_enable(data->clk_cdev1);
>>>>>        if (err) {
>>>>>            dev_err(data->dev, "Can't enable cdev1: %d\n", err);
>>>>> @@ -158,6 +176,7 @@ EXPORT_SYMBOL_GPL(tegra_asoc_utils_set_ac97_rate);
>>>>>    int tegra_asoc_utils_init(struct tegra_asoc_utils_data *data,
>>>>>                  struct device *dev)
>>>>>    {
>>>>> +    struct clk *clk_out_1_mux;
>>>>>        int ret;
>>>>>          data->dev = dev;
>>>>> @@ -196,6 +215,51 @@ int tegra_asoc_utils_init(struct
>>>>> tegra_asoc_utils_data *data,
>>>>>            goto err_put_pll_a_out0;
>>>>>        }
>>>> In a previous patch you added fallback to EXTPERIPH when clk_get(MCLK)
>>>> fails. This will work perfectly fine for the older kernels which have
>>>> all clocks in the same single CaR driver, but this may not work that
>>>> great for the newer kernels because PMC driver isn't registered early
>>>> during boot and thus it is possible to get a legit -EPROBE_DEFER which
>>>> shouldn't be ignored. In other words, you need to add into this patch a
>>>> check for the error code returned by clk_get(MCLK) and fallback only for
>>>> -EINVAL.
>>> yeah right, will add check in next version.
>>>>> +    /*
>>>>> +     * If clock parents are not set in DT, configure here to use
>>>>> clk_out_1
>>>>> +     * as mclk and extern1 as parent for Tegra30 and higher.
>>>>> +     */
>>>>> +    if (!of_find_property(dev->of_node, "assigned-clock-parents",
>>>>> NULL) &&
>>>>> +        data->soc > TEGRA_ASOC_UTILS_SOC_TEGRA20) {
>>>>> +        data->clk_extern1 = clk_get_sys("clk_out_1", "extern1");
>>>>> +        if (IS_ERR(data->clk_extern1)) {
>>>>> +            dev_err(data->dev, "Can't retrieve clk extern1\n");
>>>>> +            ret = PTR_ERR(data->clk_extern1);
>>>>> +            goto err_put_cdev1;
>>>>> +        }
>>>>> +
>>>>> +        ret = clk_set_parent(data->clk_extern1, data->clk_pll_a_out0);
>>>>> +        if (ret < 0) {
>>>>> +            dev_err(data->dev,
>>>>> +                "Set parent failed for clk extern1: %d\n",
>>>>> +                ret);
>>>>> +            goto err_put_cdev1;
>>>>> +        }
>>>>> +
>>>>> +        clk_out_1_mux = clk_get_sys(NULL, "clk_out_1_mux");
>>>> Note1: clk_get(dev, "clk_out_1_mux") should work here by letting clk
>>>> core to fall back to the clk_get_sys() by itself. Either way should
>>>> be good.
>> clk_get uses device rather and dev_id will be name of this device and
>> when clk_get fall back to __clk_get_sys() it still will use dev id of
>> this device rather than actual dev_id that pmc clocks are added to the
>> lookup. So clk_get_sys() seems to be correct to use as we can specify
>> exact dev_id and con_id.
> It should be better to use something "resource managed", thus
> devm_clk_get() should be a better choice.
>
>> Also, clk_find retrieves clock from lookup only when it finds matching
>> clock with both dev_id and con_id as pmc clocks are registered with both
>> dev_id and con_id.
>>
>> I see existing clock driver adds both extern and pmc clocks (clk_out) to
>> lookup with same dev_id of clk_out_1/2/3 and con_id of extern1/2/3 and
>> with this always extern clock will be retrieved and this is probably
>> because old DT and audio driver always uses extern1 rather than actual
>> clk_out_1
>>
>> But this need to be fixed now as we changed to use clk_out directly
>> rather than extern (even for other pmc clocks) to match actual hw design.
>>
>> Will fix this as well to register pmc clocks using con_id as
>> clk_out_1/2/3 in pmc driver and extern clocks using con_id of
>> extern1/2/3 with dev_id being NULL so we can retrieve these clocks by
>> just using con_id only using clk_get_sys as we switched to use clk_out_1
>> directly as pmc clock rather than extern from DT and no longer need to
>> pair pmc clocks to extern clocks.
> I'm not sure it's worth the effort to care about con_ids if implicit
> fallback to clk_get_sys(NULL, "...") does the right thing for the audio
> driver.
>
> IIRC, CCF uses variant of matching clocks by names, although I'm not
> sure whether that applies to older stable kernels.
>
> [snip]

Current clock driver adds EXTERN clock to lookup with dev_id as 
clk_out_1/2/3 and con_id as extern_1/2/3

With this we can retrieve clock from lookup only with clk_get_sys where 
we can pass dev_id as clk_out_1/2/3 and con_id as extern_1/2/3.

We cant use devm_clk_get() or clk_get() for retrieving clocks from 
lookup by passing device object from sound driver as dev_id will be diff 
and clk_find will return NULL.


But with the fix of having dev_id as NULL and use only con_id to add to 
lookup, we can use resource managed APIs devm_clk_get.

So was saying will fix this in clock driver as part of removing 
clk_out_1/2/3 ids and pmc init from clock driver so we can use 
devm_clk_get API in audio driver.

>

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