linux-kernel - Re: [PATCH v4 13/19] ASoC: tegra: Add fallback implementation for audio mclk

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Date:   Wed, 18 Dec 2019 07:43:40 -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>,
        <robh+dt@...nel.org>, <mark.rutland@....com>
CC:     <pdeschrijver@...dia.com>, <pgaikwad@...dia.com>,
        <spujar@...dia.com>, <josephl@...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>
Subject: Re: [PATCH v4 13/19] ASoC: tegra: Add fallback implementation for
 audio mclk


On 12/17/19 11:31 PM, Dmitry Osipenko wrote:
> 18.12.2019 10:22, Dmitry Osipenko пишет:
>> 18.12.2019 10:14, Sowjanya Komatineni пишет:
>>> On 12/17/19 11:01 PM, Dmitry Osipenko wrote:
>>>> 18.12.2019 09:59, Dmitry Osipenko пишет:
>>>>> 17.12.2019 23:04, Sowjanya Komatineni пишет:
>>>>>> mclk is from clk_out_1 which is part of Tegra PMC block and pmc clocks
>>>>>> are moved to Tegra PMC driver with pmc as clock provider and using pmc
>>>>>> clock ids.
>>>>>>
>>>>>> New device tree uses clk_out_1 from pmc clock provider.
>>>>>>
>>>>>> So, this patch adds implementation for mclk fallback to extern1 when
>>>>>> retrieving mclk returns -ENOENT to be backward compatible of new device
>>>>>> tree with older kernels.
>>>>>>
>>>>>> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
>>>>>> ---
>>>>>>    sound/soc/tegra/tegra_asoc_utils.c | 11 ++++++++++-
>>>>>>    1 file changed, 10 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/sound/soc/tegra/tegra_asoc_utils.c
>>>>>> b/sound/soc/tegra/tegra_asoc_utils.c
>>>>>> index fe9ca8acd0fb..1b88c6043082 100644
>>>>>> --- a/sound/soc/tegra/tegra_asoc_utils.c
>>>>>> +++ b/sound/soc/tegra/tegra_asoc_utils.c
>>>>>> @@ -191,7 +191,16 @@ int tegra_asoc_utils_init(struct
>>>>>> tegra_asoc_utils_data *data,
>>>>>>        data->clk_cdev1 = devm_clk_get(dev, "mclk");
>>>>>>        if (IS_ERR(data->clk_cdev1)) {
>>>>>>            dev_err(data->dev, "Can't retrieve clk cdev1\n");
>>>>>> -        return PTR_ERR(data->clk_cdev1);
>>>>>> +        if (PTR_ERR(data->clk_cdev1) != -ENOENT)
>>>>>> +            return PTR_ERR(data->clk_cdev1);
>>>>>> +        /* Fall back to extern1 */
>>>>>> +        data->clk_cdev1 = devm_clk_get(dev, "extern1");
>>>>>> +        if (IS_ERR(data->clk_cdev1)) {
>>>>>> +            dev_err(data->dev, "Can't retrieve clk extern1\n");
>>>>>> +            return PTR_ERR(data->clk_cdev1);
>>>>>> +        }
>>>>>> +
>>>>>> +        dev_err(data->dev, "Falling back to extern1\n");
>>>>>>        }
>>>>>>          /*
>>>>>>
>>>>> [    1.769091] ------------[ cut here ]------------
>>>>> [    1.769249] WARNING: CPU: 2 PID: 1 at drivers/clk/clk.c:954
>>>>> clk_core_disable+0xa5/0x1d4
>>>>> [    1.769330] clk_out_1 already disabled
>>>>> [    1.769459] Modules linked in:
>>>>> [    1.769541] CPU: 2 PID: 1 Comm: swapper/0 Not tainted
>>>>> 5.5.0-rc1-next-20191213-00167-g6b9fbcdac8f3-dirty #266
>>>>> [    1.769676] Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
>>>>> [    1.769775] [<c010e4bd>] (unwind_backtrace) from [<c010a0fd>]
>>>>> (show_stack+0x11/0x14)
>>>>> [    1.769918] [<c010a0fd>] (show_stack) from [<c09a37b1>]
>>>>> (dump_stack+0x85/0x94)
>>>>> [    1.770061] [<c09a37b1>] (dump_stack) from [<c011f3d1>]
>>>>> (__warn+0xc1/0xc4)
>>>>> [    1.770144] [<c011f3d1>] (__warn) from [<c011f691>]
>>>>> (warn_slowpath_fmt+0x61/0x78)
>>>>> [    1.770285] [<c011f691>] (warn_slowpath_fmt) from [<c04a0e7d>]
>>>>> (clk_core_disable+0xa5/0x1d4)
>>>>> [    1.770427] [<c04a0e7d>] (clk_core_disable) from [<c04a0fc3>]
>>>>> (clk_core_disable_lock+0x17/0x20)
>>>>> [    1.770516] [<c04a0fc3>] (clk_core_disable_lock) from [<c07792bb>]
>>>>> (tegra_asoc_utils_set_rate+0x53/0x208)
>>>>> [    1.770662] [<c07792bb>] (tegra_asoc_utils_set_rate) from
>>>>> [<c077b8c5>] (tegra_rt5640_probe+0xd5/0x128)
>>>>> [    1.770808] [<c077b8c5>] (tegra_rt5640_probe) from [<c0555eb7>]
>>>>> (platform_drv_probe+0x33/0x68)
>>>>> [    1.770958] [<c0555eb7>] (platform_drv_probe) from [<c055471d>]
>>>>> (really_probe+0x14d/0x240)
>>>>> [    1.771099] [<c055471d>] (really_probe) from [<c055493f>]
>>>>> (driver_probe_device+0x43/0x11c)
>>>>> [    1.771187] [<c055493f>] (driver_probe_device) from [<c0554b25>]
>>>>> (device_driver_attach+0x3d/0x40)
>>>>> [    1.771328] [<c0554b25>] (device_driver_attach) from [<c0554b5f>]
>>>>> (__driver_attach+0x37/0x78)
>>>>> [    1.771469] [<c0554b5f>] (__driver_attach) from [<c05532fb>]
>>>>> (bus_for_each_dev+0x43/0x6c)
>>>>> [    1.771609] [<c05532fb>] (bus_for_each_dev) from [<c0553e0f>]
>>>>> (bus_add_driver+0xe3/0x148)
>>>>> [    1.771692] [<c0553e0f>] (bus_add_driver) from [<c055531d>]
>>>>> (driver_register+0x39/0xa0)
>>>>> [    1.771833] [<c055531d>] (driver_register) from [<c0102c2f>]
>>>>> (do_one_initcall+0x43/0x1bc)
>>>>> [    1.771979] [<c0102c2f>] (do_one_initcall) from [<c1000ce5>]
>>>>> (kernel_init_freeable+0x121/0x194)
>>>>> [    1.772129] [<c1000ce5>] (kernel_init_freeable) from [<c09b40e9>]
>>>>> (kernel_init+0xd/0xd0)
>>>>> [    1.772215] [<c09b40e9>] (kernel_init) from [<c01010bd>]
>>>>> (ret_from_fork+0x11/0x34)
>>>>> [    1.772349] Exception stack(0xde907fb0 to 0xde907ff8)
>>>>>
>>>> Although, that's probably related to the "ASoC: tegra: Add initial
>>>> parent configuration for audio mclk".
>>>>
>>> Actually I see these warnings of already unprepared and already disabled
>>> for pll_a, pll_a_out0, and clk_out_1 even without this whole patch
>>> series as well.
>>>
>>> I think its from tegra_asoc_utils_set_rate() doing clk_disable_unprepare
>>> and these clocks are already unprepared and disabled so its just warning
>>> from clk_core_unprepare and clk_core_disable.
>> Doesn't happen for me without this series.

I looked at wrong log, right earlier clock driver keeps them enabled so 
asoc_utils_set_rate() disables the clock fine but now enabling audio 
clock should be done in asoc_utils_init() to let the 
clk_disable_unprepare from asoc_utils_set_rate not to show this warning.

But actually we don't need to have clock enabled in asoc_utils_init 
prior to invoking asoc_utils_set_rate from utils_init and its just warns 
during sound driver probe because clock is already in disabled state. At 
same time it doesn't harm to have it kept enabled in utils_init. So will 
keep it enabled in asoc_utils_init to prevent this warning to show up.

> But sound works with both old/new device-trees.