linux-kernel - Re: [PATCH 2/5] pwm: Add support for the MSTAR MSC313 PWM

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Date:   Fri, 19 Aug 2022 16:44:53 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Romain Perier <romain.perier@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Lee Jones <lee.jones@...aro.org>,
        Daniel Palmer <daniel@...f.com>,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-pwm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] pwm: Add support for the MSTAR MSC313 PWM

Hello Romain,

On Fri, Aug 19, 2022 at 03:12:56PM +0200, Romain Perier wrote:
> Le dim. 19 juin 2022 à 23:35, Uwe Kleine-König
> <u.kleine-koenig@...gutronix.de> a écrit :
> > > +static void msc313e_pwm_writecounter(struct regmap_field *low, struct regmap_field *high, u32 value)
> > > +{
> > > +     regmap_field_write(low, value);
> > > +     regmap_field_write(high, value >> 16);
> >
> > Is this racy? E.g. if the hw is running and the low register overflows
> > before the high register is updated?
> >
> 
> Ack, I am re-working most of the stuff you noticed. The problem with
> this IP blocks (and others...) is we have close registers
> but we only need to write or read 16 bits in each of these (it is
> mainly reverse engineered from vendor source or runtime most of the
> time) . You cannot really do a single read (except by doing an obscur
> thing via readq ? ...)

This is fine, but pleast document that in a comment.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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