linux-kernel - Re: [PATCH v6 2/2] pwm: add support for NXPs high-side switch MC33XS2410

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <atkj7wnhl4n6frl5swjwrto6r6dhofjtnqisqrn5z6w3cmfl3h@dgqgdxovrqb4>
Date: Sun, 3 Nov 2024 21:19:36 +0100
From: Uwe Kleine-König <u.kleine-koenig@...libre.com>
To: Dimitri Fedrau <dima.fedrau@...il.com>
Cc: Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, linux-pwm@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/2] pwm: add support for NXPs high-side switch
 MC33XS2410

Hello Dimitri,

On Sun, Nov 03, 2024 at 08:07:09PM +0100, Dimitri Fedrau wrote:
> Am Thu, Oct 24, 2024 at 11:19:16PM +0200 schrieb Uwe Kleine-König:
> > What breaks if you drop the check for state->enabled?
> >  
> The device is unable to generate a 0% duty cycle, to support this you
> proposed in an earlier review to disable the output. Without checking if
> the output is disabled, the mc33xs2410_pwm_get_state function returns the
> wrong duty cycle for a previously setted 0% duty cycle. A "0" value in the
> MC33XS2410_PWM_DC register means that the relative duty cylce is 1/256. As
> a result there are complaints if PWM_DEBUG is enabled.

I fail to follow. If .enabled=true + .duty_cycle=0 is requested you
disable. That's fine. However it shouldn't be necessary to use
state->enabled in .get_state(). I didn't look at the actual code, but if
you provide a sequence of writes to /sys that trigger a PWM_DEBUG
output, I'll take another look.

Best regards
Uwe

Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)