[PATCH v2] gpio: mxs: implement get_direction callback

[Janusz Uzycki]

gpiolib's gpiod_get_direction() function returns the EINVAL error
if .get_direction callback is not defined.
The patch implements the callback for mxs chip what is useful
for debugging.

Commit f9e42397d79b
("serial: mxs-auart: add interrupts for modem control lines")
as based on commit ab5e4e4108ca
("tty/serial: at91: add interrupts for modem control lines")
uses the gpiod_get_direction() function.

Inspired from arch/arm/mach-at91/gpio.c

Signed-off-by: Janusz Uzycki <j.uzycki at elproma.com.pl>
---

Changes since v1:
- Fix the explanation why the patch is needed

Two patches were missed during movements between our internal repos.
The 2/2 patch is required against commits:
  f9e42397d79b ("serial: mxs-auart: add interrupts for modem control lines")
  36a262782b04 ("serial: mxs-auart: enable PPS support")
I've done build-test for the next only before.
I should have done hardware test also for the next, sorry.
Now it is tested for the next on real hardware too.

On the moment the patch is required to get the patch
"serial: mxs-auart: enable PPS support" working.
It is planned to introduce new mctrl_gpio helpers to avoid
gpiod_get_direction() function.

---
 drivers/gpio/gpio-mxs.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/gpio/gpio-mxs.c b/drivers/gpio/gpio-mxs.c
index 8ffdd7d..56052c2 100644
--- a/drivers/gpio/gpio-mxs.c
+++ b/drivers/gpio/gpio-mxs.c
@@ -227,6 +227,18 @@ static int mxs_gpio_to_irq(struct gpio_chip *gc, unsigned offset)
 	return irq_find_mapping(port->domain, offset);
 }
 
+static int mxs_gpio_get_direction(struct gpio_chip *gc, unsigned offset)
+{
+	struct bgpio_chip *bgc = to_bgpio_chip(gc);
+	struct mxs_gpio_port *port =
+		container_of(bgc, struct mxs_gpio_port, bgc);
+	u32 mask = 1 << offset;
+	u32 dir;
+
+	dir = readl(port->base + PINCTRL_DOE(port));
+	return !(dir & mask);
+}
+
 static struct platform_device_id mxs_gpio_ids[] = {
 	{
 		.name = "imx23-gpio",
@@ -320,6 +332,7 @@ static int mxs_gpio_probe(struct platform_device *pdev)
 		goto out_irqdesc_free;
 
 	port->bgc.gc.to_irq = mxs_gpio_to_irq;
+	port->bgc.gc.get_direction = mxs_gpio_get_direction;
 	port->bgc.gc.base = port->id * 32;
 
 	err = gpiochip_add(&port->bgc.gc);
-- 
1.7.11.3