From: Maxime Ripard <maxime@cerno.tech>
To: Kevin Tang <kevin3.tang@gmail.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Sean Paul <sean@poorly.run>, David Airlie <airlied@linux.ie>,
Daniel Vetter <daniel@ffwll.ch>, Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Orson Zhai <orsonzhai@gmail.com>,
Chunyan Zhang <zhang.lyra@gmail.com>,
"Linux-Kernel@Vger. Kernel. Org" <linux-kernel@vger.kernel.org>,
ML dri-devel <dri-devel@lists.freedesktop.org>,
devicetree@vger.kernel.org
Subject: Re: [PATCH v4 4/6] drm/sprd: add Unisoc's drm display controller driver
Date: Wed, 21 Apr 2021 12:00:52 +0200 [thread overview]
Message-ID: <20210421100052.gujzkrafp26e6tcz@gilmour> (raw)
In-Reply-To: <CAFPSGXYdA=09xWZJi2oCQsbr3eH1GBgzjD8DRm5=beiKAtx37Q@mail.gmail.com>
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On Mon, Apr 19, 2021 at 07:01:00AM +0800, Kevin Tang wrote:
> Maxime Ripard <maxime@cerno.tech> 于2021年4月15日周四 下午5:03写道:
> > On Thu, Apr 15, 2021 at 08:18:52AM +0800, Kevin Tang wrote:
> > > Maxime Ripard <maxime@cerno.tech> 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
Yeah, you need to initialize it for drm_of_find_possible_crtcs to work,
but my point was that you shouldn't do it through of_parse_phandle, just
put the output of_graph_get_port_by_id like you found in those drivers.
Maxime
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next prev parent reply other threads:[~2021-04-21 10:01 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-22 13:28 [PATCH v4 0/6] Add Unisoc's drm kms module Kevin Tang
2021-02-22 13:28 ` [PATCH v4 1/6] dt-bindings: display: add Unisoc's drm master bindings Kevin Tang
2021-02-22 13:28 ` [PATCH v4 2/6] drm/sprd: add Unisoc's drm kms master Kevin Tang
2021-02-22 20:55 ` Orson Zhai
2021-03-24 10:53 ` Maxime Ripard
2021-04-08 10:21 ` Thomas Zimmermann
[not found] ` <CAFPSGXZ2o9YRAMax3ZeiyQ5bMtqOsSODMW8V7dXHZSD3gyzbQw@mail.gmail.com>
2021-04-09 13:57 ` Thomas Zimmermann
2021-02-22 13:28 ` [PATCH v4 3/6] dt-bindings: display: add Unisoc's dpu bindings Kevin Tang
2021-02-22 13:28 ` [PATCH v4 4/6] drm/sprd: add Unisoc's drm display controller driver Kevin Tang
2021-03-24 11:10 ` Maxime Ripard
[not found] ` <CAFPSGXZ3DjKt87Kc=wc9YKVzTjkQ38Ok6HnHm+VEdqXyHv54Eg@mail.gmail.com>
2021-04-07 10:45 ` Maxime Ripard
2021-04-08 3:05 ` Chunyan Zhang
[not found] ` <CAFPSGXa3xsxmfVquN_pTyBJ4+kL4jQAj6sK+86G3SA2OhB7Jtg@mail.gmail.com>
2021-04-15 9:09 ` Maxime Ripard
2021-04-15 0:18 ` Kevin Tang
2021-04-15 9:03 ` Maxime Ripard
2021-04-18 23:01 ` Kevin Tang
2021-04-21 10:00 ` Maxime Ripard [this message]
2021-04-08 10:53 ` Thomas Zimmermann
2021-02-22 13:28 ` [PATCH v4 5/6] dt-bindings: display: add Unisoc's mipi dsi controller bindings Kevin Tang
2021-03-24 11:13 ` Maxime Ripard
[not found] ` <CAFPSGXah3gKKHXhukRAPT=RjQZTnvDznG+619+8tah-hfFrUzA@mail.gmail.com>
2021-04-07 10:46 ` Maxime Ripard
[not found] ` <CAFPSGXaQKeKMKC7MGXhxQErB_yh_eE8khk1hOrjHnuOH20Gg4Q@mail.gmail.com>
2021-04-15 8:42 ` Maxime Ripard
2021-04-18 16:33 ` Kevin Tang
2021-04-21 9:38 ` Maxime Ripard
2021-02-22 13:28 ` [PATCH v4 6/6] drm/sprd: add Unisoc's drm mipi dsi&dphy driver Kevin Tang
[not found] ` <20210324112745.n76qhrbhzyfunmkd@gilmour>
[not found] ` <CAFPSGXYK0Hi2-eYkukO2pNhHrJVZ=f79sj_hjXnGBZ_meVmkFg@mail.gmail.com>
2021-04-07 10:48 ` Maxime Ripard
2021-04-15 0:19 ` Kevin Tang
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