From: Thierry Reding <thierry.reding@gmail.com>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: Enric Balletbo i Serra <enric.balletbo@collabora.com>,
linux-pwm@vger.kernel.org
Subject: Re: [PATCH] Revert "pwm: Let pwm_get_state() return the last implemented state"
Date: Mon, 21 Oct 2019 16:17:21 +0200 [thread overview]
Message-ID: <20191021141721.GA1476994@ulmo> (raw)
In-Reply-To: <20191021111847.c5j4qycyqy5wmynh@pengutronix.de>
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On Mon, Oct 21, 2019 at 01:18:47PM +0200, Uwe Kleine-König wrote:
> On Mon, Oct 21, 2019 at 12:58:30PM +0200, Thierry Reding wrote:
> > It turns out that commit 01ccf903edd6 ("pwm: Let pwm_get_state() return
> > the last implemented state") causes backlight failures on a number of
> > boards. The reason is that some of the drivers do not write the full
> > state through to the hardware registers, which means that ->get_state()
> > subsequently does not return the correct state. Consumers which rely on
> > pwm_get_state() returning the current state will therefore get confused
> > and subsequently try to program a bad state.
> >
> > Before this change can be made, existing drivers need to be more
> > carefully audited and fixed to behave as the framework expects. Until
> > then, keep the original behaviour of returning the software state that
> > was applied rather than reading the state back from hardware.
>
> I would really prefer to fix that in the framework instead. This is
There's nothing to fix in the framework. The framework isn't broken, the
drivers are.
> something that affects several drivers (cros-ec, imx27, atmel, imx-tpm,
> lpss, meson, sifive, sprd and stm32-lp). This is im my eyes really
> sufficient to justify a framework wide solution instead of adapting
> several drivers in a way that doesn't affect the values programmed to
> hardware.
Can you come up with a proposal for how to want to implement this in the
framework?
Thierry
> > Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
>
> Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
>
> Thanks
> Uwe
>
> --
> Pengutronix e.K. | Uwe Kleine-König |
> Industrial Linux Solutions | http://www.pengutronix.de/ |
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next prev parent reply other threads:[~2019-10-21 14:17 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-21 10:58 [PATCH] Revert "pwm: Let pwm_get_state() return the last implemented state" Thierry Reding
2019-10-21 11:18 ` Uwe Kleine-König
2019-10-21 14:17 ` Thierry Reding [this message]
2019-10-21 21:25 ` Uwe Kleine-König
2019-10-21 13:33 ` Enric Balletbo i Serra
2019-10-21 13:55 ` Michal Vokáč
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