Date:   Tue, 17 Dec 2019 08:39:26 -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 8:16 AM, Dmitry Osipenko wrote:
> 17.12.2019 19:12, Sowjanya Komatineni пишет:
>> 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.
> Have you actually tried to test that it fails? I think it's a false
> assumption.

Yes I tried and looking at devm_clk_get it falls back to __clk_get_sys 
which uses dev_id as dev_name of the device we pass from audio driver.

looking into clk_find API implementation it doesn't find the clock from 
lookup unless both dev_id and con_id matches if a clock is added to 
lookup with both dev_id and clk_id


>> 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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