linux-kernel - Re: [PATCH] sound/tlv320dac33: Add device tree support

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Date:   Tue, 30 Jan 2018 10:11:02 +0100
From:   Filip Matijević <filip.matijevic.pz@...il.com>
To:     Pavel Machek <pavel@....cz>, Ladislav Michl <ladis@...ux-mips.org>
Cc:     lgirdwood@...il.com, broonie@...nel.org, robh+dt@...nel.org,
        mark.rutland@....com, perex@...ex.cz, tiwai@...e.com,
        bhumirks@...il.com, alsa-devel@...a-project.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        pali.rohar@...il.com, sre@...nel.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-omap@...r.kernel.org, tony@...mide.com, khilman@...nel.org,
        aaro.koskinen@....fi, ivo.g.dimitrov.75@...il.com,
        patrikbachan@...il.com, serge@...lyn.com, abcloriens@...il.com,
        clayton@...ftyguy.net, martijn@...xit.nl,
        sakari.ailus@...ux.intel.com
Subject: Re: [PATCH] sound/tlv320dac33: Add device tree support

Hi,

On 01/30/2018 09:53 AM, Pavel Machek wrote:
> On Tue 2018-01-30 09:34:46, Ladislav Michl wrote:
>> On Tue, Jan 30, 2018 at 12:33:01AM +0100, Pavel Machek wrote:
>>> On Tue 2018-01-30 00:20:31, Ladislav Michl wrote:
>>>> On Tue, Jan 30, 2018 at 12:05:39AM +0100, Pavel Machek wrote:
>>>>>
>>>>> This adds device tree support to tlv320dac33.c.
>>>>>
>>>>> Signed-off-by: Pavel Machek <pavel@....cz>
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/sound/tlv320dac33.txt b/Documentation/devicetree/bindings/sound/tlv320dac33.txt
>>>>> new file mode 100644
>>>>> index 0000000..6cbd311
>>>>> --- /dev/null
>>>>> +++ b/Documentation/devicetree/bindings/sound/tlv320dac33.txt
>>>>> @@ -0,0 +1,32 @@
>>>>> +Texas Instruments - tlv320dac33 Codec module
>>>>> +
>>>>> +The tlv320dac33 serial control bus communicates through I2C protocols.
>>>>> +
>>>>> +Required properties:
>>>>> +
>>>>> +- compatible - "ti,tlv320dac33"
>>>>> +- reg - I2C slave address
>>>>> +
>>>>> +Optional properties:
>>>>> +
>>>>> +- power-gpios - gpio pin to power the device, active high
>>>>
>>>> While driver used gpio in platform data, isn't it more likely
>>>> regulator which powers device?
>>>
>>>                 power-gpios = <&gpio2 28 0>; /* gpio_60 */
>>>
>>> Looks like GPIO to me -- example is from Nokia N9. So this appears to
>>> be correct.
>>
>> Device datasheet doesn't list any pin which looks like "power-gpio"
>> http://www.ti.com/lit/ds/symlink/tlv320dac32.pdf
>> Unfortunately I do not know much about N9, but was able to find Nokia 5610
>> scheme to get clue how could be tlv320dac33 hardwired (see page 2):
>> http://mastermobile.spb.ru/service/nokia_5610_rm-242_service_schematics.pdf
>> Here AVDD is powered by LP3985 voltage regulator which is enabled using
>> VEN pin which might be connected to gpio. Or there could be completely
>> different voltage regulator with different controls. And since Linux
>> already has voltage regulator class, lets not limit ourselves to gpio
>> pins.
> 
> Well, notice I'm converting existing driver to device tree. And that
> one already has GPIO dependency. It is possible that more work needs
> to be done there, but that should not be a reason to delay this. Feel
> free to help.
> 
> 									Pavel
> 

According to N9 schematics
http://www.s-manuals.com/manuals/phone/nokia/nokia_n9_rm-696_service_schematics_v1.pdf
it's in fact GPIO pin that is connected to reset line (labeled
CODEC_RST). So calling it "power" might be misleading, but the driver
code is quite clear as it labels that GPIO as "tlv320dac33 reset"

Filip