Re: [PATCH] pinctrl: baytrail: show output gpio state correctly on Intel Baytrail

Felipe Balbi
2014-10-13T19:14:18Z

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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 ?

--
balbi

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