Re: [PATCH v3 070/105] drm/vc4: hdmi: rework connectors and encoders

On Wed, May 27, 2020 at 11:41:24AM -0700, Eric Anholt wrote:

On Wed, May 27, 2020 at 8:51 AM Maxime Ripard maxime@cerno.tech wrote:

...

the vc4_hdmi driver has some custom structures to hold the data it needs to associate with the drm_encoder and drm_connector structures.

However, it allocates them separately from the vc4_hdmi structure which makes it more complicated than it needs to be.

Move those structures to be contained by vc4_hdmi and update the code accordingly.

...

@@ -1220,7 +1219,7 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data) struct drm_device *drm = dev_get_drvdata(master); struct vc4_dev *vc4 = drm->dev_private; struct vc4_hdmi *hdmi;

•   struct vc4_hdmi_encoder *vc4_hdmi_encoder;
  

•   struct drm_encoder *encoder;
    struct device_node *ddc_node;
    u32 value;
    int ret;
  

@@ -1229,14 +1228,10 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data) if (!hdmi) return -ENOMEM;

•   vc4_hdmi_encoder = devm_kzalloc(dev, sizeof(*vc4_hdmi_encoder),
  

•                                   GFP_KERNEL);
  

•   if (!vc4_hdmi_encoder)
  

•           return -ENOMEM;
  

•   vc4_hdmi_encoder->base.type = VC4_ENCODER_TYPE_HDMI0;
  

•   hdmi->encoder = &vc4_hdmi_encoder->base.base;
  

•   hdmi->pdev = pdev;
  

•   encoder = &hdmi->encoder.base.base;
  

•   encoder->base.type = VC4_ENCODER_TYPE_HDMI0;
  

Wait, does this patch build?

All those patches were build tested, so yep

setting struct drm_encoder->base.type = VC4_* seems very wrong, when previously we were setting struct vc4_hdmi_encoder->base.type (struct vc4_encoder->type).

So the structure layout now is that vc4_hdmi embeds vc4_hdmi_encoder as encoder. So &hdmi->encoder is a pointer to vc4_hdmi_encoder. vc4_hdmi_encoder's base is since that patch a struct vc4_encoder. and vc4_encoder's base is a drm_encoder.

so encoder being a drm_encoder is correct there.

However, drm_encoder's base is drm_mode_object that does have a type field, which is an uint32_t, which will accept a VC4_ENCODER_TYPE_* just fine...

Now, drm_encoder_init will then kick in and call drm_mode_object_add which will override it to a proper value and since the clock select bit in the PV is the same for both HDMI0 and HDMI1, everything works just fine...

Good catch, I'll fix it. And I guess it's a good indication we don't need a separate HDMI0 and HDMI1 encoder type.

Other than this, patch 68-78 r-b.

Thanks for your review! Maxime