On 3/22/22 15:29, Tobias Waldekranz wrote:
Support using GPO lines (i.e. GPIOs that are output-only) with
gpio_wdt using the "toggle" algorithm.
Since its inception, gpio_wdt has configured its GPIO line as an input
when using the "toggle" algorithm, even though it is used as an output
when kicking. This needlessly barred hardware with output-only pins
from using the driver.
Signed-off-by: Tobias Waldekranz <tobias@xxxxxxxxxxxxxx>
---
Hi,
This patch has been in our downstream tree for a long time. We need it
because our kick GPIO can't be used as an input.
What I really can't figure out is why the driver would request the pin
as in input, when it's always going to end up being used as an output
anyway.
So I thought I'd send it upstream in the hopes of either getting it
merged, or an explanation as to why it is needed.
I _think_ the assumption / idea was that "toggle" implies that the output
is connected to a pull-up resistor and that the pin either floats or is
pulled down to ground, causing the signal to toggle. I don't know if/how
that works in practice, though.
Guenter
drivers/watchdog/gpio_wdt.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)
diff --git a/drivers/watchdog/gpio_wdt.c b/drivers/watchdog/gpio_wdt.c
index 0923201ce874..f7686688e0e2 100644
--- a/drivers/watchdog/gpio_wdt.c
+++ b/drivers/watchdog/gpio_wdt.c
@@ -108,7 +108,6 @@ static int gpio_wdt_probe(struct platform_device *pdev)
struct device *dev = &pdev->dev;
struct device_node *np = dev->of_node;
struct gpio_wdt_priv *priv;
- enum gpiod_flags gflags;
unsigned int hw_margin;
const char *algo;
int ret;
@@ -122,17 +121,15 @@ static int gpio_wdt_probe(struct platform_device *pdev)
ret = of_property_read_string(np, "hw_algo", &algo);
if (ret)
return ret;
- if (!strcmp(algo, "toggle")) {
+
+ if (!strcmp(algo, "toggle"))
priv->hw_algo = HW_ALGO_TOGGLE;
- gflags = GPIOD_IN;
- } else if (!strcmp(algo, "level")) {
+ else if (!strcmp(algo, "level"))
priv->hw_algo = HW_ALGO_LEVEL;
- gflags = GPIOD_OUT_LOW;
- } else {
+ else
return -EINVAL;
- }
- priv->gpiod = devm_gpiod_get(dev, NULL, gflags);
+ priv->gpiod = devm_gpiod_get(dev, NULL, GPIOD_OUT_LOW);
if (IS_ERR(priv->gpiod))
return PTR_ERR(priv->gpiod);
