[6/6,v2] drm/msm/hdmi: Do not initialize HPD line value

Message ID 20190823073448.8385-6-linus.walleij@linaro.org
State New
Headers show
  • [1/6,v2] drm/msm/mdp4: Drop unused GPIO include
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Commit Message

Linus Walleij Aug. 23, 2019, 7:34 a.m.
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@gmail.com>
Cc: Sean Paul <sean@poorly.run>
Cc: linux-arm-msm@vger.kernel.org
Cc: freedreno@lists.freedesktop.org
Reviewed-by: Brian Masney <masneyb@onstation.org>

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

ChangeLog v1->v2:
- Rebased on v5.3-rc1
- Collected review tag
 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 f006682935e9..bb1c49e3c9dd 100644
--- a/drivers/gpu/drm/msm/hdmi/hdmi_connector.c
+++ b/drivers/gpu/drm/msm/hdmi/hdmi_connector.c
@@ -76,7 +76,7 @@  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);