linux-kernel - Re: [PATCH V1 5/5] backlight: qcom-wled: Add auto string detection logic

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Message-ID: <5477037fff5d6f6ef335221220b527b6@codeaurora.org>
Date:   Tue, 15 May 2018 10:20:45 +0530
From:   kgunda@...eaurora.org
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Lee Jones <lee.jones@...aro.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-leds@...r.kernel.org, linux-arm-msm-owner@...r.kernel.org
Subject: Re: [PATCH V1 5/5] backlight: qcom-wled: Add auto string detection
 logic

On 2018-05-14 22:32, Bjorn Andersson wrote:
> On Wed 09 May 00:14 PDT 2018, kgunda@...eaurora.org wrote:
> 
>> On 2018-05-07 23:40, Bjorn Andersson wrote:
>> > On Thu 03 May 02:57 PDT 2018, Kiran Gunda wrote:
>> >
>> > [..]
>> > > +
>> > > +#define WLED_AUTO_DETECT_OVP_COUNT		5
>> > > +#define WLED_AUTO_DETECT_CNT_DLY_US		HZ /* 1 second */
>> > > +static bool wled_auto_detection_required(struct wled *wled)
>> >
>> > So cfg.auto_detection_enabled is set, but we didn't have a fault during
>> > wled_auto_detection_at_init(), which I presume indicates that the boot
>> > loader configured the strings appropriately (or didn't enable the BL).
>> > Then first time we try to enable the backlight we will hit the ovp irq,
>> > which will  enter here a few times to figure out that the strings are
>> > incorrectly configured and then we will do the same thing that would
>> > have been done if we probed with a fault.
>> >
>> > This is convoluted!
>> >
>> > If auto-detection is a feature allowing the developer to omit the string
>> > configuration then just do the auto detection explicitly in probe when
>> > the developer did so and then never do it again.
>> >
>> As explained in the previous patch, the auto-detection is needed 
>> later,
>> because are also cases where one/more of the connected LED string of 
>> the
>> display-backlight is malfunctioning (because of damage) and requires 
>> the
>> damaged string to be turned off to prevent the complete panel and/or 
>> board
>> from being damaged.
> 
> Okay, that sounds very reasonable. Please ensure that it's clearly
> described in the commit message, so that we have this documented if
> someone wonders in the future.
> 
> Regards,
> Bjorn
> --
Thanks for that ! Sure I will describe it in the commit message.
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