Date:   Tue, 17 Dec 2019 19:46:30 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.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

17.12.2019 19:39, Sowjanya Komatineni пишет:
> 
> 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.
>>>

Ok

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