Hi,

On Thu, Jan 30, 2020 at 08:20:55AM +0200, Stefan Mavrodiev wrote:

On 1/29/20 6:43 PM, Maxime Ripard wrote:

quoted

On Tue, Jan 28, 2020 at 04:06:42PM +0200, Stefan Mavrodiev wrote:

quoted

diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
index 68d4644ac2dc..4cd35c97c503 100644
--- a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
+++ b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c

@@ -23,6 +23,8 @@
  #include <drm/drm_print.h>
  #include <drm/drm_probe_helper.h>

+#include <sound/soc.h>
+
  #include "sun4i_backend.h"
  #include "sun4i_crtc.h"
  #include "sun4i_drv.h"

@@ -87,6 +89,10 @@ static void sun4i_hdmi_disable(struct drm_encoder *encoder)

  	DRM_DEBUG_DRIVER("Disabling the HDMI Output\n");

+#ifdef CONFIG_DRM_SUN4I_HDMI_AUDIO
+	sun4i_hdmi_audio_destroy(hdmi);
+#endif
+
  	val = readl(hdmi->base + SUN4I_HDMI_VID_CTRL_REG);
  	val &= ~SUN4I_HDMI_VID_CTRL_ENABLE;
  	writel(val, hdmi->base + SUN4I_HDMI_VID_CTRL_REG);

@@ -114,6 +120,11 @@ static void sun4i_hdmi_enable(struct drm_encoder *encoder)
  		val |= SUN4I_HDMI_VID_CTRL_HDMI_MODE;

  	writel(val, hdmi->base + SUN4I_HDMI_VID_CTRL_REG);
+
+#ifdef CONFIG_DRM_SUN4I_HDMI_AUDIO
+	if (hdmi->hdmi_audio && sun4i_hdmi_audio_create(hdmi))
+		DRM_ERROR("Couldn't create the HDMI audio adapter\n");
+#endif

I really don't think we should be creating / removing the audio card
at enable / disable time.

For me it's unnatural to have sound card all the time, even when the HDMI
is not plugged-in.

It's also a matter of being consistent: pretty much everyone else is
doing it:
  * vc4 (RaspberryPi)
    https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/vc4/vc4_hdmi.c#L1437

  * omap
    https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/omapdrm/dss/hdmi4.c#L620

  * sti
    https://elixir.bootlin.com/linux/v5.5.1/source/drivers/gpu/drm/sti/sti_hdmi.c#L1310

  * msm
    https://elixir.bootlin.com/linux/v5.5.1/source/drivers/gpu/drm/msm/hdmi/hdmi.c#L597

etc...

If we were to think about this at a more theorical level though, it's
pretty much the same case than having a sound card but no headphone
attached, or having a display engine but no display attached. In both
case, you register the driver before having a sink, you just let the
userspace know that there's nothing connected on the other end.

Maxime