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

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Message-ID: <c4e20767-2263-7a29-f50c-d36876ad58e2@nvidia.com>
Date:   Wed, 18 Dec 2019 08:32:07 -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 12/18/19 8:29 AM, Dmitry Osipenko wrote:
> 18.12.2019 18:43, Sowjanya Komatineni пишет:
>> 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.
> The rule of thumb: don't enable anything when it shouldn't be enabled.
> If clocks are disabled at the time of drivers probe, then drivers
> shouldn't disable the clocks.
Will fix asoc_utils_set_rate to disable only when its enabled.