Re: [PATCH V7 6/6] backlight: qcom-wled: Add auto string detection logic

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On 2019-10-17 19:00, Lee Jones wrote:
On Thu, 17 Oct 2019, kgunda@xxxxxxxxxxxxxx wrote:

On 2019-10-17 17:56, Lee Jones wrote:
> On Wed, 16 Oct 2019, Kiran Gunda wrote:
>
> > The auto string detection algorithm checks if the current WLED
> > sink configuration is valid. It tries enabling every sink and
> > checks if the OVP fault is observed. Based on this information
> > it detects and enables the valid sink configuration.
> > Auto calibration will be triggered when the OVP fault interrupts
> > are seen frequently thereby it tries to fix the sink configuration.
> >
> > The auto-detection also kicks in when the connected LED string
> > of the display-backlight malfunctions (because of damage) and
> > requires the damaged string to be turned off to prevent the
> > complete panel and/or board from being damaged.
> >
> > Signed-off-by: Kiran Gunda <kgunda@xxxxxxxxxxxxxx>
> > ---
> >  drivers/video/backlight/qcom-wled.c | 410
> > +++++++++++++++++++++++++++++++++++-
> >  1 file changed, 404 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/video/backlight/qcom-wled.c
> > b/drivers/video/backlight/qcom-wled.c
> > index b5b125c..ff7c409 100644
> > --- a/drivers/video/backlight/qcom-wled.c
> > +++ b/drivers/video/backlight/qcom-wled.c

[...]

> > +		if (int_sts & WLED3_CTRL_REG_OVP_FAULT_STATUS)
> > +			dev_dbg(wled->dev, "WLED OVP fault detected with SINK %d\n",
> > +				i + 1);
>
> I haven't reviewed the whole patch, but this caught my eye.
>
> I think this should be upgraded to dev_warn().
>
Thought of keeping these messages silent, Because the string configuration
will be corrected in this
and informing it at end of the auto string detection.

[...]

> > +	} else {
> > +		dev_warn(wled->dev, "New WLED string configuration found %x\n",
> > +			 sink_valid);
>
> Why would the user care about this?  Is it not normal?
>
Actually, it comes here if the user provided string configuration in the
device tree is in-correct.
That's why just informing the user about the right string configuration,
after the auto string detection.

Then I think we need to be more forthcoming.  Tell the user the
configuration is incorrect and what you've done to rectify it.

"XXX is not a valid configuration - using YYY instead"

Sure. Will update it in the next series.
[...]

> > +static int wled_configure_ovp_irq(struct wled *wled,
> > +				  struct platform_device *pdev)
> > +{
> > +	int rc;
> > +	u32 val;
> > +
> > +	wled->ovp_irq = platform_get_irq_byname(pdev, "ovp");
> > +	if (wled->ovp_irq < 0) {
> > +		dev_dbg(&pdev->dev, "ovp irq is not used\n");
>
> I assume this is optional.  What happens if no IRQ is provided?
>
Here OVP IRQ is used to detect the wrong string detection. If it is not
provided the auto string detection logic won't work.

"OVP IRQ not found - disabling automatic string detection"

Sure. Will update it in the next series.
> If, for instance, polling mode is enabled, maybe something like this
> would be better?
>
>       dev_warn(&pdev->dev, "No IRQ found, falling back to polling
> mode\n");



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