linux-kernel - Re: [PATCH 1/4] gpio: mvebu: Add limited PWM support

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Message-ID: <20170320134440.GN22463@ulmo.ba.sec>
Date:   Mon, 20 Mar 2017 14:44:40 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Ralph Sennhauser <ralph.sennhauser@...il.com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Andrew Lunn <andrew@...n.ch>, Imre Kaloz <kaloz@...nwrt.org>,
        Alexandre Courbot <gnurou@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "David S. Miller" <davem@...emloft.net>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        "open list:PWM SUBSYSTEM" <linux-pwm@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] gpio: mvebu: Add limited PWM support

On Thu, Mar 16, 2017 at 05:03:05PM +0100, Linus Walleij wrote:
> On Thu, Mar 16, 2017 at 7:42 AM, Ralph Sennhauser
> <ralph.sennhauser@...il.com> wrote:
> 
> > From: Andrew Lunn <andrew@...n.ch>
> >
> > Armada 370/XP devices can 'blink' gpio lines with a configurable on
> > and off period. This can be modelled as a PWM.
> >
> > However, there are only two sets of PWM configuration registers for
> > all the gpio lines. This driver simply allows a single gpio line per
> > gpio chip of 32 lines to be used as a PWM. Attempts to use more return
> > EBUSY.
> >
> > Due to the interleaving of registers it is not simple to separate the
> > PWM driver from the gpio driver. Thus the gpio driver has been
> > extended with a PWM driver.
> >
> > Signed-off-by: Andrew Lunn <andrew@...n.ch>
> > URL: https://patchwork.ozlabs.org/patch/427287/
> > URL: https://patchwork.ozlabs.org/patch/427295/
> > [Ralph Sennhauser:
> >   * port forward
> >   * merge pwm portion into gpio-mvebu.c
> >   * merge doc patch
> >   * update MAINAINERS]
> > Signed-off-by: Ralph Sennhauser <ralph.sennhauser@...il.com>
> 
> In essence I am very positive of this patch set and happy to merge
> it as a PWM driver inside of GPIO if Thierry is OK with it.

No objections to the concept of making a GPIO driver implement a PWM
chip when it makes sense.

Thierry

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