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@xxxxxxxxxxxxxxx> # v3.14+ > > > Signed-off-by: David Cohen <david.a.cohen@xxxxxxxxxxxxxxx> > > > --- > > > > > > 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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