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

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Message-ID: <20190827164538.GB52127@atomide.com>
Date:   Tue, 27 Aug 2019 09:45:38 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     Dan Murphy <dmurphy@...com>
Cc:     Pavel Machek <pavel@....cz>, 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

* Dan Murphy <dmurphy@...com> [190827 16:20]:
> Tony
> 
> On 8/27/19 11:04 AM, Tony Lindgren wrote:
> > * Dan Murphy <dmurphy@...com> [190827 13:02]:
> > > Hello
> > > 
> > > On 8/27/19 7:44 AM, Dan Murphy wrote:
> > > > Tony
> > > > 
> > > > On 8/27/19 7:18 AM, Pavel Machek wrote:
> > > > > 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?
> > > > With only setting CONFIG_LEDS_LM3532=m to the next branch I get full
> > > > brightness with 255.
> > > > 
> > > > I also see half brightness at 128 with the ramp down working.
> > > > 
> > > > I am not able to reproduce this issue on my device.
> > > > 
> > > Just to make sure my data was right I did a clean rebuild on commit
> > > 1dbb9fb4082ce2a2f1cf9596881ddece062d15d0
> > > 
> > > from the led-next branch.
> > > 
> > > Just adding the above config flag.  I still cannot reproduce the issue
> > > 
> > > See attached pic
> > OK thanks for checking. Probably you can reproduce the issue if you
> > reset things to commit c4b8354e5341 ("leds: lm3532: Fix brightness
> > control for i2c mode"). There might now be something uninitialized
> > with that commit depending on the hardware state on boot if you
> > care to check that. Or maybe there's some interaction with other
> > patches not yet at commit c4b8354e5341 level.
> 
> Ok the fix for that issue is in this patch
> 
> leds: lm3532: Fixes for the driver for stability
> 
> The fix for setting the brightness control register during the init forced
> the ALS mode to
> 
> be enabled.  The Fixes for driver stability patch then set the led->mode to
> the correct register setting.

OK yeah so that part starts to make sense now. I wonder if the reason
for my issues was caused by change in sysfs brightness level values
and I ended up chasing an already fixed issue. I think I was using
value of 30 recently, which is now very dim :)

> > I confirmed again that things fail at commit c4b8354e5341. But
> > now testing with the same Linux next as yesterday things works again.
> > Not sure what's going on as failures with Linux next yestreday
> > made me start narrowing down what commit causes the issues.
> > 
> > Anyways, playing with loading and unloading the leds-lm3532.ko I
> > noticed we can also have unpaired regulator calls when using sysfs
> > brightness that the below patch attempts to fix. Not sure how I got
> > to the point of regulator warnings, but I was trying to enable
> > the brightness via sysfs. Maybe I had other patches too when
> > I got the regulator warnings.. But please check if the below
> > patch makes sense.
> 
> Makes sense did you want me to push a patch?

No need to, I can send out a proper patch later today after typing up
the patch description if no other comments.

Regards,

Tony