linux-kernel - Re: [PATCH v3 1/2] leds: mt6360: Add LED driver for MT6360

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Date:   Fri, 11 Sep 2020 07:24:31 +0800
From:   Gene Chen <gene.chen.richtek@...il.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Jacek Anaszewski <jacek.anaszewski@...il.com>, robh+dt@...nel.org,
        Matthias Brugger <matthias.bgg@...il.com>,
        Dan Murphy <dmurphy@...com>, linux-leds@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Gene Chen <gene_chen@...htek.com>, Wilma.Wu@...iatek.com,
        shufan_lee@...htek.com, cy_huang@...htek.com,
        benjamin.chao@...iatek.com
Subject: Re: [PATCH v3 1/2] leds: mt6360: Add LED driver for MT6360

Pavel Machek <pavel@....cz> 於 2020年9月11日 週五 下午3:05寫道：
>
> Hi!
>
> > >+{
> > >+    struct mt6360_led *led = container_of(lcdev, struct mt6360_led, flash.led_cdev);
> > >+    struct mt6360_priv *priv = led->priv;
> > >+    u32 enable_mask = MT6360_TORCHEN_MASK | MT6360_FLCSEN_MASK(led->led_no);
> > >+    u32 val = (level) ? MT6360_FLCSEN_MASK(led->led_no) : 0;
> > >+    u32 prev = priv->fled_torch_used, curr;
> > >+    int ret;
> > >+
> > >+    dev_dbg(lcdev->dev, "[%d] brightness %d\n", led->led_no, level);
> > >+    if (priv->fled_strobe_used) {
> > >+            dev_warn(lcdev->dev, "Please disable strobe first [%d]\n", priv->fled_strobe_used);
> >
> > Doesn't hardware handle that? IOW, what happens when you have enabled
> > both torch and flash? If flash just overrides torch mode, than you
> > should not prevent enabling torch in this case.
>
> Yep, this is strange/confusing... and was reason why I asked for not
> supporting strobe from sysfs.
>
> Could I get you to remove code you are not commenting at when
> reviewing?
>

MT6360 FLED register define is STROBE_EN/TORCH_EN/CS1/CS2 (current
source) 4 bits.
The STROBE_EN/TORCH_EN is shared by FLED1 and FLED2.
If I want to enable FLED1 torch mode, I set TORCH_EN and CS1
If I want to enable FLED2 strobe mode, I set STROBE_EN and CS2
For example I set FLED1 torch, then I set FLED2 strobe.
When I set FLED2 strobe, I will see the strobe current is FLED2 add
FLED1 current which is not I want.
So I need disable FLED1 torch first.
Considering every circumstances is complicated when share same H/W
logic control.
And the other problem is torch mode switch to strobe mode needs ramp
time because strobe and torch mode can't be co-exist.

> > >+MODULE_AUTHOR("Gene Chen <gene_chen@...htek.com>");
> > >+MODULE_DESCRIPTION("MT6360 Led Driver");
>
> Led -> LED.
>

ACK

>                                                                         Pavel
> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html