lkml.org 
[lkml]   [2017]   [Aug]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 2/2] gpio: 74x164: handling enable-gpios
Hi Peng,

On Mon, Aug 7, 2017 at 9:27 AM, Peng Fan <peng.fan@nxp.com> wrote:
> To 74hc595 and 74lv595, there is an OE(low active) input pin.
> To some boards, this pin is controller by GPIO, so handling
> this pin in driver. When driver probe, use GPIOD_OUT_LOW flag
> when requesting the gpio, so OE is set to low when probe.

Well, this depends of the GPIO polarity.

>
> Signed-off-by: Peng Fan <peng.fan@nxp.com>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> ---
> drivers/gpio/gpio-74x164.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/gpio/gpio-74x164.c b/drivers/gpio/gpio-74x164.c
> index a6607fa..e44422c 100644
> --- a/drivers/gpio/gpio-74x164.c
> +++ b/drivers/gpio/gpio-74x164.c
> @@ -23,6 +23,7 @@ struct gen_74x164_chip {
> struct gpio_chip gpio_chip;
> struct mutex lock;
> u32 registers;
> + struct gpio_desc *enable_gpio;
> /*
> * Since the registers are chained, every byte sent will make
> * the previous byte shift to the next register in the
> @@ -142,6 +143,12 @@ static int gen_74x164_probe(struct spi_device *spi)
> chip->gpio_chip.parent = &spi->dev;
> chip->gpio_chip.owner = THIS_MODULE;
>
> + chip->enable_gpio = devm_gpiod_get(&spi->dev, "enable", GPIOD_OUT_LOW);

It would be better to use devm_gpiod_get_optional instead.

> + if (IS_ERR(chip->enable_gpio)) {
> + dev_dbg(&spi->dev, "No enable-gpios property\n");
> + chip->enable_gpio = NULL;
> + }
> +
> mutex_init(&chip->lock);
>
> ret = __gen_74x164_write_config(chip);
> @@ -164,6 +171,8 @@ static int gen_74x164_remove(struct spi_device *spi)
> {
> struct gen_74x164_chip *chip = spi_get_drvdata(spi);
>
> + if (chip->enable_gpio)
> + gpiod_set_value(chip->enable_gpio, 0);

It would be better to use the cansleep variant instead.

Actually I have worked on adding this optional property, but haven't
submitted yet:
https://pastebin.com/u839DVD3

\
 
 \ /
  Last update: 2017-08-07 14:36    [W:0.060 / U:3.164 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site