linux-kernel - Re: [PATCH v7 15/21] ASoC: tegra: Add fallback implementation for audio mclk

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Date:   Fri, 10 Jan 2020 14:13:42 -0800
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Sameer Pujar <spujar@...dia.com>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <broonie@...nel.org>,
        <lgirdwood@...il.com>, <perex@...ex.cz>, <tiwai@...e.com>,
        <mperttunen@...dia.com>, <gregkh@...uxfoundation.org>,
        <sboyd@...nel.org>, <robh+dt@...nel.org>, <mark.rutland@....com>
CC:     <pdeschrijver@...dia.com>, <pgaikwad@...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 v7 15/21] ASoC: tegra: Add fallback implementation for
 audio mclk


On 1/10/20 2:05 PM, Dmitry Osipenko wrote:
> External email: Use caution opening links or attachments
>
>
> 10.01.2020 20:04, Sowjanya Komatineni пишет:
>> On 1/9/20 10:52 AM, Sowjanya Komatineni wrote:
>>>
>>> On 1/7/20 10:28 PM, Sameer Pujar wrote:
>>>> On 1/8/2020 11:18 AM, Sowjanya Komatineni wrote:
>>>>> On 1/7/20 9:34 PM, Sameer Pujar wrote:
>>>>>> On 1/8/2020 9:55 AM, Sowjanya Komatineni wrote:
>>>>>>> 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.
>>>>>>>
>>>>>>> Tested-by: Dmitry Osipenko <digetx@...il.com>
>>>>>>> Reviewed-by: Dmitry Osipenko <digetx@...il.com>
>>>>>>> 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 9cfebef74870..9a5f81039491 100644
>>>>>>> --- a/sound/soc/tegra/tegra_asoc_utils.c
>>>>>>> +++ b/sound/soc/tegra/tegra_asoc_utils.c
>>>>>>> @@ -183,7 +183,16 @@ 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");
>>>>>> This error print can be moved inside below if, when this actually
>>>>>> meant to be an error condition.
>>>>>>
>>>>> Want to show error even if mclk retrieval returns ENOENT to clearly
>>>>> indicate mclk does not exist along with message of falling back to
>>>>> extern1.
>>>> Yes, but falling back essentially means 'mclk' is not available and
>>>> fallback print is not an error.
>>>> Not a major issue though, you can consider updating. Otherwise LGTM.
>>>>
>>> Will update
>>>>>>> -        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");
>>>>>> This can be a info print?
>>> Will use dev_info
>>>>>>>        }
>>>>>>>          /*
>>> Dmitry/Rob, there was discussion in v3 regarding backporting mclk
>>> fallback.
>>>
>>> Dmitry wanted Rob to confirm on this
>>>
>>> I think openSUSE Leap could be one of those distros that use LTS kernel
>>> with newer device-trees, but that's not 100%. Maybe Rob could help
>>> clarifying that.
>>>
>>> Dmitry/Rob, Can you please confirm if mclk fallback patch need
>>> backport to have new device tree work with old kernels?
>>>
>> Dmitry,
>>
>> Can you please confirm if we need to backport this mclk fallback patch?
>>
> Seems only T210 was making use of the CaR's TEGRA*_CLK_CLK_OUT_*, thus
> the backporting isn't needed.
Thanks Dmitry
>
> Also, please use 'git rebase --exec make ...' to make sure that all
> patches are compiling without problems. The removal of the legacy clock
> IDs should be done after the device-trees changes, otherwise it looks
> like DTBs compilation will fail. It's possible that the order of the
> patches could be changed if Thierry will chose to split this series into
> several pull requests, nevertheless all patches should compile and work
> in the original order.
OK, Will move patches of device tree updates to use new DT ID prior to 
removal of old ID.