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drm: sun4i: hdmi: Remove extra HPD polling

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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>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20200629060032.24134-1-wens@kernel.org
This commit is contained in:
Chen-Yu Tsai 2020-06-29 14:00:32 +08:00 committed by Maxime Ripard
parent 4ab59c3c63
commit bda8eaa6de
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GPG Key ID: E3EF0D6F671851C5
1 changed files with 2 additions and 3 deletions
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5
drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
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@ -259,9 +259,8 @@ sun4i_hdmi_connector_detect(struct drm_connector *connector, bool force)
struct sun4i_hdmi *hdmi = drm_connector_to_sun4i_hdmi(connector); struct sun4i_hdmi *hdmi = drm_connector_to_sun4i_hdmi(connector);
unsigned long reg; unsigned long reg;
if (readl_poll_timeout(hdmi->base + SUN4I_HDMI_HPD_REG, reg, reg = readl(hdmi->base + SUN4I_HDMI_HPD_REG);
reg & SUN4I_HDMI_HPD_HIGH, if (reg & SUN4I_HDMI_HPD_HIGH) {
0, 500000)) {
cec_phys_addr_invalidate(hdmi->cec_adap); cec_phys_addr_invalidate(hdmi->cec_adap);
return connector_status_disconnected; return connector_status_disconnected;
} }