After untangling the MSM HDMI GPIO code we see that the code is deliberately setting the output value of the HPD (hot plug detect) line to high, even though it is being used as input which is of course the only viable use of a HPD pin. This seems dubious: GPIO lines set up as input will have high impedance (tristate) and the typical electronic construction involves this line being used with a pull-down resistor around 10KOhm to keep it low (this is sometimes part of a levelshifter component) and then an inserted connector will pull it up to VDD and this asserts the HPD signal, as can be seen from the code reading the HPD GPIO. Stop try driving a value to the HPD input GPIO. Cc: Rob Clark <robdclark@xxxxxxxxx> Cc: Sean Paul <sean@xxxxxxxxxx> Cc: linux-arm-msm@xxxxxxxxxxxxxxx Cc: freedreno@xxxxxxxxxxxxxxxxxxxxx Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx> --- drivers/gpu/drm/msm/hdmi/hdmi_connector.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/msm/hdmi/hdmi_connector.c b/drivers/gpu/drm/msm/hdmi/hdmi_connector.c index 89c64cc85027..ecbcd8638b66 100644 --- a/drivers/gpu/drm/msm/hdmi/hdmi_connector.c +++ b/drivers/gpu/drm/msm/hdmi/hdmi_connector.c @@ -87,7 +87,7 @@ static int gpio_config(struct hdmi *hdmi, bool on) struct hdmi_gpio_data gpio = config->gpios[i]; /* The value indicates the value for turning things on */ - if (gpio.gpiod) + if (gpio.gpiod && gpio.output) gpiod_set_value_cansleep(gpio.gpiod, gpio.value); } -- 2.20.1
