Hi,
Maxime Ripard <maxime@xxxxxxxxxx> 于2021年4月15日周四 下午5:03写道：
>
> Hi,
>
> On Thu, Apr 15, 2021 at 08:18:52AM +0800, Kevin Tang wrote:
> > Maxime Ripard <maxime@xxxxxxxxxx> 于2021年3月24日周三 下午7:10写道：
> > > > +static struct sprd_dpu *sprd_crtc_init(struct drm_device *drm,
> > > > + struct drm_plane *primary)
> > > > +{
> > > > + struct device_node *port;
> > > > + struct sprd_dpu *dpu;
> > > > +
> > > > + /*
> > > > + * set crtc port so that drm_of_find_possible_crtcs call works
> > > > + */
> > > > + port = of_parse_phandle(drm->dev->of_node, "ports", 0);
> > > > + if (!port) {
> > > > + drm_err(drm, "find 'ports' phandle of %s failed\n",
> > > > + drm->dev->of_node->full_name);
> > > > + return ERR_PTR(-EINVAL);
> > > > + }
> > > > + of_node_put(port);
> > >
> > > The YAML binding should already make sure that your binding is sane, and
> > > if you still get a DT that doesn't follow it, you have a whole lot of
> > > other issues than whether ports is there :)
> > >
> > > > + dpu = drmm_crtc_alloc_with_planes(drm, struct sprd_dpu, base,
> > > > + primary, NULL,
> > > > + &sprd_crtc_funcs, NULL);
> > > > + if (IS_ERR(dpu)) {
> > > > + drm_err(drm, "failed to init crtc.\n");
> > > > + return dpu;
> > > > + }
> > > > +
> > > > + dpu->base.port = port;
> > >
> > > But you're still referencing it here, while you called of_node_put on it
> > > already? You should only call it once you're done with it.
> >
> > of_node_put should be called after done with it, this maybe indeed be a bug.
> > i will fix it.
> > >
> > >
> > > I'm not really sure why you would need drm_of_find_possible_crtcs to
> > > work then if you don't follow the OF-Graph bindings.
> >
> > it scan all endports of encoder, if a matching crtc is found by
> > OF-Graph bindings
> > and then genarate the crtc mask, here is description:
> > 41 /**
> > 42 * drm_of_find_possible_crtcs - find the possible CRTCs for an encoder port
> > 43 * @dev: DRM device
> > 44 * @port: encoder port to scan for endpoints
> > 45 *
> > 46 * Scan all endpoints attached to a port, locate their attached CRTCs,
> > 47 * and generate the DRM mask of CRTCs which may be attached to this
> > 48 * encoder.
> > 49 *
> > if we don't follow the OF-Graph bindings, crtc can't attched to encoder.
>
> Yeah, what I'm actually confused about is why you would need the
> of_parse_phandle call. You usually call drm_of_find_possible_crtcs with
> the encoder device node, so from your MIPI-DSI driver in your case, and
> with it's device->of_node pointer and it should work perfectly fine?
I still confused about use drm_of_find_possible_crtcs to bind crtc and
encoder, the port of drm_crtc, default is null?
709 /**
710 * struct drm_crtc - central CRTC control structure
711 * @dev: parent DRM device
712 * @port: OF node used by drm_of_find_possible_crtcs()
-----------------------------------------------------------------------------------------------------
25 static uint32_t drm_crtc_port_mask(struct drm_device *dev,
26 struct device_node *port)
27 {
28 unsigned int index = 0;
29 struct drm_crtc *tmp;
30
31 drm_for_each_crtc(tmp, dev) {
32 if (tmp->port == port)
33 return 1 << index;
34
35 index++;
36 }
37
38 return 0;
39 }
I did not see any place to initialize the port of drm_crtc in the drm
framework, if not setup it.
it looks like the port of drm_crtc is undefined.
https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/rockchip/rockchip_drm_vop.c#L1851
https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/tilcdc/tilcdc_crtc.c#L1051
The difference from others is that we use of_parse_phandle,
as you said, follow the OF-Graph bindings , should be also use
of_get_child_by_name replace it?
like this:
-----------------------------------------------------------------------------------
struct device_node *port;
port = of_get_child_by_name(dpu->dev->of_node, "port");
if (!port) {
DRM_ERROR("find 'ports' phandle of %s failed\n",
dpu->dev->of_node->full_name);
return -EINVAL;
}
crtc->port = port;
of_node_put(port);
------------------------------------------------------------------------------------
If we have multiple display controllers, use of_parse_phandle by
different index also seem is ok.
display-subsystem {
compatible = "sprd,display-subsystem";
ports = <&dpu0_port, &dpu1_port, &dpu2_port......>;
};
dpu0_port = of_parse_phandle(drm->dev->of_node, "ports", 0);
dpu1_port = of_parse_phandle(drm->dev->of_node, "ports", 1);
dpu2_port = of_parse_phandle(drm->dev->of_node, "ports", 2);
>
> Maxime
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