* [PATCH] drm: sun4i: hdmi: Remove extra HPD polling
@ 2020-06-29 6:00 Chen-Yu Tsai
2020-06-30 8:02 ` Maxime Ripard
0 siblings, 1 reply; 2+ messages in thread
From: Chen-Yu Tsai @ 2020-06-29 6:00 UTC (permalink / raw)
To: Maxime Ripard, David Airlie, Daniel Vetter
Cc: Chen-Yu Tsai, dri-devel, linux-arm-kernel, linux-kernel
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(-)
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;
}
--
2.27.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] drm: sun4i: hdmi: Remove extra HPD polling
2020-06-29 6:00 [PATCH] drm: sun4i: hdmi: Remove extra HPD polling Chen-Yu Tsai
@ 2020-06-30 8:02 ` Maxime Ripard
0 siblings, 0 replies; 2+ messages in thread
From: Maxime Ripard @ 2020-06-30 8:02 UTC (permalink / raw)
To: Chen-Yu Tsai
Cc: David Airlie, Daniel Vetter, Chen-Yu Tsai, dri-devel,
linux-arm-kernel, linux-kernel
[-- Attachment #1: Type: text/plain, Size: 986 bytes --]
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
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