Re: [PATCH 1/2] backlight: lm3630a: add an enable gpio for the HWEN pin

Daniel Thompson
2019-09-09T10:57:35Z

On Sun, Sep 08, 2019 at 10:37:03PM +0200, Andreas Kemnade wrote:
> For now just enable it in the probe function to allow i2c
> access and disable it on remove. Disabling also means resetting
> the register values to default.
>
> Tested on Kobo Clara HD.
>
> Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
> ---
> drivers/video/backlight/lm3630a_bl.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/drivers/video/backlight/lm3630a_bl.c b/drivers/video/backlight/lm3630a_bl.c
> index b04b35d007a2..3b45a1733198 100644
> --- a/drivers/video/backlight/lm3630a_bl.c
> +++ b/drivers/video/backlight/lm3630a_bl.c
> @@ -12,6 +12,8 @@
> #include <linux/uaccess.h>
> #include <linux/interrupt.h>
> #include <linux/regmap.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/gpio.h>
> #include <linux/pwm.h>
> #include <linux/platform_data/lm3630a_bl.h>
>
> @@ -48,6 +50,7 @@ struct lm3630a_chip {
> struct lm3630a_platform_data *pdata;
> struct backlight_device *bleda;
> struct backlight_device *bledb;
> + struct gpio_desc *enable_gpio;
> struct regmap *regmap;
> struct pwm_device *pwmd;
> };
> @@ -506,6 +509,14 @@ static int lm3630a_probe(struct i2c_client *client,
> return -ENOMEM;
> pchip->dev = &client->dev;
>
> + pchip->enable_gpio = devm_gpiod_get_optional(&client->dev, "enable",
> + GPIOD_ASIS);

Initializing GPIOD_ASIS doesn't look right to me.

If you initialize ASIS then the driver must configure the pin as an
output... far easier just to set GPIOD_OUT_HIGH during the get.

Note also that the call to this function should also be moved *below*
the calls parse the DT.

> + if (IS_ERR(pchip->enable_gpio)) {
> + rval = PTR_ERR(pchip->enable_gpio);
> + return rval;
> + }
> +
> +
> pchip->regmap = devm_regmap_init_i2c(client, &lm3630a_regmap);
> if (IS_ERR(pchip->regmap)) {
> rval = PTR_ERR(pchip->regmap);
> @@ -535,6 +546,10 @@ static int lm3630a_probe(struct i2c_client *client,
> }
> pchip->pdata = pdata;
>
> + if (pchip->enable_gpio) {
> + gpiod_set_value_cansleep(pchip->enable_gpio, 1);

Not needed, use GPIOD_OUT_HIGH instead.

> + usleep_range(1000, 2000);

Not needed, this sleep is already part of lm3630a_chip_init().

> + }
> /* chip initialize */
> rval = lm3630a_chip_init(pchip);
> if (rval < 0) {
> @@ -586,6 +601,9 @@ static int lm3630a_remove(struct i2c_client *client)
> if (rval < 0)
> dev_err(pchip->dev, "i2c failed to access register\n");
>
> + if (pchip->enable_gpio)
> + gpiod_set_value_cansleep(pchip->enable_gpio, 0);
> +

Is this needed?

This is a remove path, not a power management path, and we have no idea
what the original status of the pin was anyway?

> if (pchip->irq) {
> free_irq(pchip->irq, pchip);
> flush_workqueue(pchip->irqthread);
> --
> 2.20.1
>