diff mbox series

drm: sun4i: hdmi: Remove extra HPD polling

Message ID 20200629060032.24134-1-wens@kernel.org (mailing list archive)
State Mainlined
Commit bda8eaa6dee7525f4dac950810a85a88bf6c2ba0
Headers show
Series drm: sun4i: hdmi: Remove extra HPD polling | expand

Commit Message

Chen-Yu Tsai June 29, 2020, 6 a.m. UTC 
From: Chen-Yu Tsai <wens@csie.org>

The HPD sense mechanism in Allwinner's old HDMI encoder hardware is more
or less an input-only GPIO. Other GPIO-based HPD implementations
directly return the current state, instead of polling for a specific
state and returning the other if that times out.

Remove the I/O polling from sun4i_hdmi_connector_detect() and directly
return a known state based on the current reading. This also gets rid
of excessive CPU usage by kworker as reported on Stack Exchange [1] and
Armbian forums [2].

 [1] https://superuser.com/questions/1515001/debian-10-buster-on-cubietruck-with-bug-in-sun4i-drm-hdmi
 [2] https://forum.armbian.com/topic/14282-headless-systems-and-sun4i_drm_hdmi-a10a20/

Fixes: 9c5681011a0c ("drm/sun4i: Add HDMI support")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
---
 drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

Comments

Maxime Ripard June 30, 2020, 8:02 a.m. UTC | #1 
Hi,

On Mon, Jun 29, 2020 at 02:00:32PM +0800, Chen-Yu Tsai wrote:
> From: Chen-Yu Tsai <wens@csie.org>
> 
> The HPD sense mechanism in Allwinner's old HDMI encoder hardware is more
> or less an input-only GPIO. Other GPIO-based HPD implementations
> directly return the current state, instead of polling for a specific
> state and returning the other if that times out.
> 
> Remove the I/O polling from sun4i_hdmi_connector_detect() and directly
> return a known state based on the current reading. This also gets rid
> of excessive CPU usage by kworker as reported on Stack Exchange [1] and
> Armbian forums [2].
> 
>  [1] https://superuser.com/questions/1515001/debian-10-buster-on-cubietruck-with-bug-in-sun4i-drm-hdmi
>  [2] https://forum.armbian.com/topic/14282-headless-systems-and-sun4i_drm_hdmi-a10a20/
> 
> Fixes: 9c5681011a0c ("drm/sun4i: Add HDMI support")
> Signed-off-by: Chen-Yu Tsai <wens@csie.org>

Applied, thanks for figuring that out

Maxime
diff mbox series

Patch

diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
index ce07ddc3e058..557cbe5ab35f 100644
--- a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
+++ b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
@@ -259,9 +259,8 @@  sun4i_hdmi_connector_detect(struct drm_connector *connector, bool force)
 	struct sun4i_hdmi *hdmi = drm_connector_to_sun4i_hdmi(connector);
 	unsigned long reg;
 
-	if (readl_poll_timeout(hdmi->base + SUN4I_HDMI_HPD_REG, reg,
-			       reg & SUN4I_HDMI_HPD_HIGH,
-			       0, 500000)) {
+	reg = readl(hdmi->base + SUN4I_HDMI_HPD_REG);
+	if (reg & SUN4I_HDMI_HPD_HIGH) {
 		cec_phys_addr_invalidate(hdmi->cec_adap);
 		return connector_status_disconnected;
 	}