linux-kernel - Re: [PATCH v3 1/5] leds: lm3532: Fix brightness control for i2c mode

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Date:   Tue, 27 Aug 2019 14:18:18 +0200
From:   Pavel Machek <pavel@....cz>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Dan Murphy <dmurphy@...com>, jacek.anaszewski@...il.com,
        sre@...nel.org, nekit1000@...il.com, mpartap@....net,
        merlijn@...zup.org, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/5] leds: lm3532: Fix brightness control for i2c mode

On Mon 2019-08-26 15:44:37, Tony Lindgren wrote:
> * Pavel Machek <pavel@....cz> [190826 22:14]:
> > On Mon 2019-08-26 14:58:22, Tony Lindgren wrote:
> > > Hi,
> > > 
> > > * Dan Murphy <dmurphy@...com> [190820 19:53]:
> > > > Fix the brightness control for I2C mode.  Instead of
> > > > changing the full scale current register update the ALS target
> > > > register for the appropriate banks.
> > > > 
> > > > In addition clean up some code errors and random misspellings found
> > > > during coding.
> > > > 
> > > > Tested on Droid4 as well as LM3532 EVM connected to a BeagleBoneBlack
> > > > 
> > > > Fixes: e37a7f8d77e1 ("leds: lm3532: Introduce the lm3532 LED driver")
> > > > Reported-by: Pavel Machek <pavel@....cz>
> > > > Signed-off-by: Dan Murphy <dmurphy@...com>
> > > > ---
> > > > 
> > > > v3 - Removed register define updates - https://lore.kernel.org/patchwork/patch/1114542/
> > > 
> > > Looks like starting with this patch in Linux next the LCD on droid4
> > > is so dim it's unreadable even with brightness set to 255. Setting
> > > brightness to 0 does blank it completely though.
> > > 
> > > Did something maybe break with the various patch revisions or are
> > > we now missing some dts patch?
> > 
> > Maybe missing dts patch. We should provide maximum current the LED can
> > handle... 
> 
> Or i2c control is somehow broken and only als control now works?

Well, max current led is obviously missing. Plus code does not check
the return from reading led-max-microamp.

ret = fwnode_property_read_u32(child, "led-max-microamp",
                                               &led->full_scale_current);

Untested, but something like this is neccessary according to code
review.

Signed-off-by: Pavel Machek <pavel@....cz>
								Pavel

diff --git a/arch/arm/boot/dts/omap4-droid4-xt894.dts b/arch/arm/boot/dts/omap4-droid4-xt894.dts
index 4454449..b883b84 100644
--- a/arch/arm/boot/dts/omap4-droid4-xt894.dts
+++ b/arch/arm/boot/dts/omap4-droid4-xt894.dts
@@ -395,6 +395,7 @@
 			ti,led-mode = <0>;
 			label = ":backlight";
 			linux,default-trigger = "backlight";
+			led-max-microamp = 29800;
 		};
 
 		led@1 {
@@ -402,6 +403,7 @@
 			led-sources = <1>;
 			ti,led-mode = <0>;
 			label = ":kbd_backlight";
+			led-max-microamp = 29800;
 		};
 	};
 };


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

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