Date:   Tue, 17 Dec 2019 18:36:59 +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 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]

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