Re: [PATCH 1/2] V4L: remove clock name from v4l2_clk API

[Josh Wu <josh.wu@atmel.com>]

Hi, Guennadi and Laurent

On 1/9/2015 6:47 AM, Laurent Pinchart wrote:
> Hi Guennadi and Josh,
>
> On Thursday 08 January 2015 23:37:58 Guennadi Liakhovetski wrote:
>> On Wed, 7 Jan 2015, Josh Wu wrote:
>>> On 1/7/2015 6:17 AM, Guennadi Liakhovetski wrote:
>>>> On Tue, 6 Jan 2015, Josh Wu wrote:
>>>>> Hi, Guennadi
>>>>>
>>>>> After look deep into this patch, I found you miss one line that should
>>>>> be changed as well.
>>>>> It's In function v4l2_clk_get(), there still has one line code called
>>>>> v4l2_clk_find(dev_id, id).
>>>>> You need to change it to v4l2_clk_find(dev_id, NULL) as well.
>>>>> Otherwise the code that many sensor used: v4l2_clk_get(&client->dev,
>>>>> "mclk") cannot acquired the "mclk" clock.
>>>>>
>>>>> After above changes, this patch works for me.
>>>> I think you're right, in fact, since we now don't store CCF-based
>>>> v4l2_clk wrappers on the list, this can be simplified even further, I'll
>>>> update the patch. Did you only test this patch or both?
>>> I tested both patches with Atmel-isi driver. For the 2/2 patch I applied
>>> the modification Laurent suggested.
>>> Those patches works for me.
>>>
>>> The only concern is in ov2640 I still need to acquired two v4l2 clocks:
>>>     "xvclk"  that will get the xvclk CCF clock directly.
>>>     "mclk"  that make ISI driver call his clock_start()/stop() to
>>>     enable/disable ISI's peripheral clock.
>>> If I only get xvclk clock, then the camera capture will be failed with a
>>> ISI timeout error.
>> No, this doesn't look right to me. The camera sensor has only one clock
>> input, so, it should only request one clock. Where does the clock signal
>> to the camera come from on your system?
> That's correct, the sensor driver only has one clock input, so it should just
> request the xvclk clock.
>
>> If it comes from the ISI itself, you don't need to specify the clock in
>> the DT, since the ISI doesn't produce a clock from DT. If you do want to
>> have your clock consumer (ov2640) and the supplier (ISI) properly
>> described in DT, you'll have to teach the ISI to register a CCF clock
>> source, which then will be connected to from the ov2640. If you choose not
>> to show your clock in the DT, you can just use v4l2_clk_get(dev, "xvclk")
>> and it will be handled by v4l2_clk / soc-camera / isi-atmel.
>>
>> If the closk to ov2640 is supplied by a separate clock source, then you
>> v4l2_clk_get() will connect ov2640 to it directly and soc-camera will
>> enable and disable it on power-on / -off as required.
> The ISI has no way to supply a sensor clock, the clock is supplied by a
> separate clock source.
>
>>  From your above description it looks like the clock to ov2640 is supplied
>> by a separate source, but atmel-isi's .clock_start() / .clock_stop()
>> functions still need to be called? By looking at those functions it looks
>> like they turn on and off clocks, supplying the ISI itself... Instead of
>> only turning on and off clocks, provided by the ISI to a camera sensor. If
>> my understanding is right, then this is a bug in atmel-isi and it has to
>> be fixed.
> That's correct as well, the ISI driver needs to be fixed.
>

Thanks both of you for the details. Now I got it.
Indeed, I need fix this in atmel-isi driver not in ov2640 driver.
So I will send a new patch for this, which should move the ISI 
peripheral clock enable/disable() from clock_start/stop() to 
isi_camera_add_device/remove_device().

Best Regards,
Josh Wu