From: Felipe Balbi <balbi@ti.com>
To: David Cohen <david.a.cohen@linux.intel.com>
Cc: Felipe Balbi <balbi@ti.com>, <linus.walleij@linaro.org>,
<linux-kernel@vger.kernel.org>, <linux-gpio@vger.kernel.org>,
<stable@vger.kernel.org>
Subject: Re: [PATCH] pinctrl: baytrail: show output gpio state correctly on Intel Baytrail
Date: Mon, 13 Oct 2014 14:26:32 -0500 [thread overview]
Message-ID: <20141013192632.GC29810@saruman> (raw)
In-Reply-To: <20141013192404.GB4034@psi-dev26.jf.intel.com>
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Hi,
On Mon, Oct 13, 2014 at 12:24:04PM -0700, David Cohen wrote:
> On Mon, Oct 13, 2014 at 02:14:05PM -0500, Felipe Balbi wrote:
> > On Mon, Oct 13, 2014 at 11:23:59AM -0700, David Cohen wrote:
> > > Even if a gpio pin is set to output, we still need to set INPUT_EN bit
> >
> > here you say you're setting that bit.
> >
> > > to be able to read its value. Without this change, we'll always read low
> > > level state.
> > >
> > > Cc: <stable@vger.kernel.org> # v3.14+
> > > Signed-off-by: David Cohen <david.a.cohen@linux.intel.com>
> > > ---
> > >
> > > Hi,
> > >
> > > I'm resending same v1 patch but now copying linux stable and linux gpio.
> > > This patch is meant for all linux stable trees >= v3.14.
> > >
> > > Br, David
> > > ---
> > >
> > > drivers/pinctrl/pinctrl-baytrail.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/pinctrl/pinctrl-baytrail.c b/drivers/pinctrl/pinctrl-baytrail.c
> > > index e12e5b07f6d7..c23d8ded936d 100644
> > > --- a/drivers/pinctrl/pinctrl-baytrail.c
> > > +++ b/drivers/pinctrl/pinctrl-baytrail.c
> > > @@ -318,7 +318,7 @@ static int byt_gpio_direction_output(struct gpio_chip *chip,
> > > "Potential Error: Setting GPIO with direct_irq_en to output");
> > >
> > > reg_val = readl(reg) | BYT_DIR_MASK;
> > > - reg_val &= ~BYT_OUTPUT_EN;
> > > + reg_val &= ~(BYT_OUTPUT_EN | BYT_INPUT_EN);
> >
> > but code is clearing it. Also, you're not patching byt_gpio_get(), so
> > you can't be 'reading its value' either. Quite frankly, this looks very
> > fishy to me. Comments on BYT_OUTPUT_EN and BYT_INPUT_EN states that
> > those bits are active low, meaning that clearing them enables that
> > particular feature.
> >
> > How can you enable a pin to be both OUTPUT and INPUT ? Look like what
> > you really want is:
> >
> > diff --git a/drivers/pinctrl/pinctrl-baytrail.c b/drivers/pinctrl/pinctrl-baytrail.c
> > index e12e5b0..69f882d 100644
> > --- a/drivers/pinctrl/pinctrl-baytrail.c
> > +++ b/drivers/pinctrl/pinctrl-baytrail.c
> > @@ -290,6 +290,7 @@ static int byt_gpio_direction_input(struct gpio_chip *chip, unsigned offset)
> >
> > value = readl(reg) | BYT_DIR_MASK;
> > value &= ~BYT_INPUT_EN; /* active low */
> > + value |= BYT_OUTPUT_EN; /* disable output */
> > writel(value, reg);
> >
> > spin_unlock_irqrestore(&vg->lock, flags);
> > @@ -319,6 +320,7 @@ static int byt_gpio_direction_output(struct gpio_chip *chip,
> >
> > reg_val = readl(reg) | BYT_DIR_MASK;
> > reg_val &= ~BYT_OUTPUT_EN;
> > + value |= BYT_INPUT_EN; /* disable input */
> >
> > if (value)
> > writel(reg_val | BYT_LEVEL, reg);
> >
> > completely untested however. Care to further explain why clearing both
> > bits - thus enabling both INPUT and OUTPUT - is correct ?
>
> Actually I really meant what I sent, but perhaps I misspoke during
> explanation. We need to clear the bit to enable the functionality.
>
> !BYT_INPUT_EN allows us to read the value. !BYT_OUTPUT_EN allows us to
> set a value. If we want to set a value (acting as output) and still be
> able to read via sysfs, we need to set both functionality (i.e. clear
> both bits).
>
> I'll resend the patch with a better comment.
Alright, just make sure that exposing a pin through sysfs and making it
output high, then later switching it to input works. It looks like
byt_gpio_direction_input() still needs to make sure OUTPUT is set.
--
balbi
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next prev parent reply other threads:[~2014-10-13 19:26 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-03 16:55 [PATCH] pinctrl: baytrail: show output gpio state correctly on Intel Baytrail David Cohen
2014-10-13 18:23 ` David Cohen
2014-10-13 19:14 ` Felipe Balbi
2014-10-13 19:24 ` David Cohen
2014-10-13 19:26 ` Felipe Balbi [this message]
2014-10-13 19:36 ` Felipe Balbi
2014-10-13 20:19 ` David Cohen
2014-10-28 10:15 ` Linus Walleij
2014-10-28 14:42 ` Felipe Balbi
2014-10-31 8:12 ` Linus Walleij
2014-10-31 13:20 ` Felipe Balbi
2014-10-31 16:23 ` David Cohen
2014-10-31 18:45 ` David Cohen
2014-11-03 9:24 ` Mika Westerberg
2014-11-03 15:00 ` Felipe Balbi
2014-11-03 15:27 ` Mika Westerberg
2014-11-03 15:35 ` Felipe Balbi
2014-11-03 15:42 ` Mika Westerberg
2014-11-03 15:50 ` Felipe Balbi
2014-11-03 18:42 ` Mika Westerberg
2014-11-03 20:40 ` Felipe Balbi
2014-11-04 7:51 ` Mika Westerberg
2014-11-04 14:44 ` Felipe Balbi
2014-11-03 22:19 ` David Cohen
2014-11-04 7:59 ` Mika Westerberg
2014-11-04 18:05 ` David Cohen
2014-11-04 18:57 ` Mika Westerberg
2014-11-04 19:11 ` David Cohen
2014-11-04 19:34 ` Mika Westerberg
2014-11-04 21:51 ` David Cohen
2014-11-05 8:40 ` Mika Westerberg
2014-11-14 9:40 ` Linus Walleij
2014-11-14 9:39 ` Linus Walleij
2014-11-14 9:53 ` Mika Westerberg
2014-11-14 23:19 ` Rafael J. Wysocki
2014-11-14 9:30 ` Linus Walleij
2014-11-03 15:33 ` Linus Walleij
2014-10-13 20:16 ` David Cohen
2014-10-14 17:54 ` [PATCH v2] " David Cohen
2014-10-14 18:19 ` Felipe Balbi
2014-10-28 10:17 ` Linus Walleij
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