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* [PATCH v8 00/11] drm: Fix EDID reading on ti-sn65dsi86 by introducing the DP AUX bus
@ 2021-05-25  0:01 Douglas Anderson
  2021-05-25  0:01 ` [PATCH v8 01/11] dt-bindings: display: simple: List hpd properties in panel-simple Douglas Anderson
                   ` (10 more replies)
  0 siblings, 11 replies; 25+ messages in thread
From: Douglas Anderson @ 2021-05-25  0:01 UTC (permalink / raw)
  To: Andrzej Hajda, Neil Armstrong, Laurent Pinchart, Jonas Karlman,
	Sam Ravnborg
  Cc: David Airlie, Sandeep Panda, Steev Klimaszewski, Bjorn Andersson,
	Thierry Reding, Laurent Pinchart, robdclark, Jernej Skrabec,
	Stanislav Lisovskiy, Andy Gross, Thierry Reding, devicetree,
	Thomas Zimmermann, linux-arm-msm, Stephen Boyd, Rob Herring,
	dri-devel, Douglas Anderson, Robert Foss, linux-kernel

The primary goal of this series is to try to properly fix EDID reading
for eDP panels using the ti-sn65dsi86 bridge.

Previously we had a patch that added EDID reading but it turned out
not to work at bootup. This caused some extra churn at bootup as we
tried (and failed) to read the EDID several times and also ended up
forcing us to use the hardcoded mode at boot. With this patch series I
believe EDID reading is reliable at boot now and we never use the
hardcoded mode.

High level note: in this series the EDID reading is driven by the
panel driver, not by the bridge chip driver. I believe this makes a
reasonable amount of sense since the panel driver already _could_
drive reading the EDID if provided with the DDC bus and in future
planned work we'll want to give the panel driver the DDC bus (to make
decisions based on EDID) and the AUX bus (to control the
backlight). There are also planned patches from Laurent to make
ti-sn65dsi86 able to drive full DP monitors. In that case the bridge
chip will still be in charge of reading the EDID, but it's not hard to
make this dynamic.

This series is the logical successor to the 3-part series containing
the patch ("drm/bridge: ti-sn65dsi86: Properly get the EDID, but only
if refclk") [1].

This patch was tested against drm-misc-next commit a596fcd9cbc7
("drm/panel: panel-simple: Add missing
pm_runtime_dont_use_autosuspend() calls") on a sc7180-trogdor-lazor
device.

At v8 now, the bindings patches have been beefed up from v7 and
review/ack tags were added. Also allmodconfig was fixed.

Between v2 and v3, high-level view of changes:
- stop doing the EDID caching in the core.

Between v3 and v4, high-level view of changes:
- EDID reading is actually driven by the panel driver now. See above.
- Lots of chicken-and-egg problems solved w/ sub-devices.

Between v4 and v5, high-level view of changes.
- Some of the early patches landed, so dropped from series.
- New pm_runtime_disable() fix (fixed a patch that already landed).
- Added Bjorn's tags to most patches
- Fixed problems when building as a module.
- Reordered debugfs patch and fixed error handling there.
- Dropped last patch. I'm not convinced it's safe w/out more work.

Between v5 and v6, high-level view of changes:
- Added the patch ("drm/dp: Allow an early call to register DDC i2c
  bus")
- Many patches had been landed, so only a few "controversial" ones
  left.

Between v6 and v7, high-level view of changes:
- New AUX DP bus!

Between v7 and v8, high-level view of changes:
- More bindings work.
- Fixed allmodconfig.

[1] https://lore.kernel.org/r/20210304155144.3.I60a7fb23ce4589006bc95c64ab8d15c74b876e68@changeid/

Changes in v8:
- Allow dp-aux-bus to be a module to fix allmodconfig builds
- Explain better why HPD needs to be in panel-simple in commit msg.
- Separate DP AUX bus binding is new for v8.
- ti-sn65dsi86 references the new aux bus bindings.

Changes in v7:
- Adjusted commit message to talk about DP AUX bus.
- Beefed up commit message in context of the DP AUX bus.
- List hpd properties bindings patch new for v7.
- Panel now under bridge chip instead of getting a link to ddc-i2c
- Patch introducing the DP AUX bus is new for v7.
- Patch to allow panel-simple to be DP AUX EP new for v7.
- Patch to support for DP AUX bus on ti-sn65dsi86 new for v7.
- Patch using the DP AUX for DDC new for v7.
- Remove use of now-dropped drm_dp_aux_register_ddc() call.
- Set the proper sub-device "dev" pointer in the AUX structure.
- ti-sn65dsi86: Add aux-bus child patch new for v7.

Changes in v6:
- Use new drm_dp_aux_register_ddc() calls.

Douglas Anderson (11):
  dt-bindings: display: simple: List hpd properties in panel-simple
  dt-bindings: drm: Introduce the DP AUX bus
  dt-bindings: drm/bridge: ti-sn65dsi86: Add aux-bus child
  dt-bindings: drm/aux-bus: Add an example
  drm: Introduce the DP AUX bus
  drm/panel: panel-simple: Allow panel-simple be a DP AUX endpoint
    device
  drm/panel: panel-simple: Stash DP AUX bus; allow using it for DDC
  drm/bridge: ti-sn65dsi86: Promote the AUX channel to its own sub-dev
  drm/bridge: ti-sn65dsi86: Add support for the DP AUX bus
  drm/bridge: ti-sn65dsi86: Don't read EDID blob over DDC
  arm64: dts: qcom: sc7180-trogdor: Move panel under the bridge chip

 .../bindings/display/bridge/ti,sn65dsi86.yaml |  20 +-
 .../bindings/display/dp-aux-bus.yaml          | 102 ++++++
 .../bindings/display/panel/panel-simple.yaml  |   2 +
 arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi  |  30 +-
 drivers/gpu/drm/Kconfig                       |   5 +
 drivers/gpu/drm/Makefile                      |   2 +
 drivers/gpu/drm/bridge/Kconfig                |   1 +
 drivers/gpu/drm/bridge/ti-sn65dsi86.c         | 111 ++++--
 drivers/gpu/drm/drm_dp_aux_bus.c              | 326 ++++++++++++++++++
 drivers/gpu/drm/panel/Kconfig                 |   1 +
 drivers/gpu/drm/panel/panel-simple.c          |  64 +++-
 include/drm/drm_dp_aux_bus.h                  |  57 +++
 12 files changed, 665 insertions(+), 56 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/display/dp-aux-bus.yaml
 create mode 100644 drivers/gpu/drm/drm_dp_aux_bus.c
 create mode 100644 include/drm/drm_dp_aux_bus.h

-- 
2.31.1.818.g46aad6cb9e-goog


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH v8 01/11] dt-bindings: display: simple: List hpd properties in panel-simple
  2021-05-25  0:01 [PATCH v8 00/11] drm: Fix EDID reading on ti-sn65dsi86 by introducing the DP AUX bus Douglas Anderson
@ 2021-05-25  0:01 ` Douglas Anderson
  2021-06-02 18:00   ` Rob Herring
  2021-05-25  0:01 ` [PATCH v8 02/11] dt-bindings: drm: Introduce the DP AUX bus Douglas Anderson
                   ` (9 subsequent siblings)
  10 siblings, 1 reply; 25+ messages in thread
From: Douglas Anderson @ 2021-05-25  0:01 UTC (permalink / raw)
  To: Andrzej Hajda, Neil Armstrong, Laurent Pinchart, Jonas Karlman,
	Sam Ravnborg
  Cc: robdclark, devicetree, David Airlie, linux-arm-msm,
	Douglas Anderson, Steev Klimaszewski, Bjorn Andersson,
	Stanislav Lisovskiy, Rob Herring, Thierry Reding, dri-devel,
	Stephen Boyd, Thierry Reding, linux-kernel

The HPD (Hot Plug Detect) signal is present in many (probably even
"most") eDP panels. For eDP, this signal isn't actually used for
detecting hot-plugs of the panel but is more akin to a "panel ready"
signal. After you provide power to the panel, panel timing diagrams
typically say that you should wait for HPD to be asserted (or wait a
fixed amount of time) before talking to the panel.

The panel-simple bindings describes many eDP panels and many of these
panels provide the HPD signal. We should add the HPD-related
properties to the panel-simple bindings. The HPD properties are
actually defined in panel-common.yaml, so adding them here just
documents that they are OK for panels handled by the panel-simple
bindings.

NOTE: whether or not we'd include HPD properties in the panel node is
more a property of the board design than the panel itself. For most
boards using these eDP panels everything "magically" works without
specifying any HPD properties and that's been why we haven't needed to
allow the HPD properties earlier. On these boards the HPD signal goes
directly to a dedicated "HPD" input to the eDP controller and this
connection doesn't need to be described in the device tree. The only
time the HPD properties are needed in the device tree are if HPD is
hooked up to a GPIO or if HPD is normally on the panel but isn't used
on a given board. That means that if we don't allow the HPD properties
in panel-simple then one could argue that we've got to boot all eDP
panels (or at least all those that someone could conceivably put on a
system where HPD goes to a GPIO or isn't hooked up) from panel-simple.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

Changes in v8:
- Explain better why HPD needs to be in panel-simple in commit msg.

Changes in v7:
- List hpd properties bindings patch new for v7.

 .../devicetree/bindings/display/panel/panel-simple.yaml         | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/panel/panel-simple.yaml b/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
index b3797ba2698b..4a0a5e1ee252 100644
--- a/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
+++ b/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
@@ -298,6 +298,8 @@ properties:
   enable-gpios: true
   port: true
   power-supply: true
+  no-hpd: true
+  hpd-gpios: true
 
 additionalProperties: false
 
-- 
2.31.1.818.g46aad6cb9e-goog


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH v8 02/11] dt-bindings: drm: Introduce the DP AUX bus
  2021-05-25  0:01 [PATCH v8 00/11] drm: Fix EDID reading on ti-sn65dsi86 by introducing the DP AUX bus Douglas Anderson
  2021-05-25  0:01 ` [PATCH v8 01/11] dt-bindings: display: simple: List hpd properties in panel-simple Douglas Anderson
@ 2021-05-25  0:01 ` Douglas Anderson
  2021-06-02 18:08   ` Rob Herring
  2021-05-25  0:01 ` [PATCH v8 03/11] dt-bindings: drm/bridge: ti-sn65dsi86: Add aux-bus child Douglas Anderson
                   ` (8 subsequent siblings)
  10 siblings, 1 reply; 25+ messages in thread
From: Douglas Anderson @ 2021-05-25  0:01 UTC (permalink / raw)
  To: Andrzej Hajda, Neil Armstrong, Laurent Pinchart, Jonas Karlman,
	Sam Ravnborg
  Cc: robdclark, devicetree, David Airlie, linux-arm-msm,
	Douglas Anderson, Steev Klimaszewski, Bjorn Andersson,
	Stanislav Lisovskiy, Rob Herring, dri-devel, Stephen Boyd,
	Thierry Reding, linux-kernel

We want to be able to list an eDP panel as a child of an eDP
controller node to represent the fact that the panel is connected to
the controller's DP AUX bus. Though the panel and the controller are
connected in several ways, the DP AUX bus is the primary control
interface between the two and thus makes the most sense to model in
device tree hierarchy.

Listing a panel in this way makes it possible for the panel driver to
easily get access to the DP AUX bus that it resides on, which can be
useful to help in auto-detecting the panel and for turning on various
bits.

NOTE: historically eDP panels were _not_ listed under their controller
but were listed at the top level of the device tree. This will still
be supported for backward compatibility (and while DP controller
drivers are adapted to support the new DT syntax) but should be
considered deprecated since there is no downside to listing the panel
under the controller.

For now, the DP AUX bus bindings will only support an eDP panel
underneath. It's possible it could be extended to allow having a DP
connector under it in the future.

The idea for this bus's design was hashed out over IRC [1].

[1] https://people.freedesktop.org/~cbrill/dri-log/?channel=dri-devel&date=2021-05-11

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---
My DT yaml-fu is still weak. If I did something stupid, please help me
learn how to do this better!

NOTE: there is no "Example" in this bindings file. Yikes! This is
because I wanted to keep this patch separate from the one that enables
the first eDP controller. See the patch ("dt-bindings: drm/aux-bus:
Add an example") for the example.

ALSO: if anyone else would like to be listed as a "Maintainer" in this
file then please shout!

Changes in v8:
- Separate DP AUX bus binding is new for v8.

 .../bindings/display/dp-aux-bus.yaml          | 37 +++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/dp-aux-bus.yaml

diff --git a/Documentation/devicetree/bindings/display/dp-aux-bus.yaml b/Documentation/devicetree/bindings/display/dp-aux-bus.yaml
new file mode 100644
index 000000000000..5e4afe9f98fb
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/dp-aux-bus.yaml
@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/dp-aux-bus.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: DisplayPort AUX bus
+
+maintainers:
+  - Douglas Anderson <dianders@chromium.org>
+
+description:
+  DisplayPort controllers provide a control channel to the sinks that
+  are hooked up to them. This is the DP AUX bus. Over the DP AUX bus
+  we can query properties about a sink and also configure it. In
+  particular, DP sinks support DDC over DP AUX which allows tunneling
+  a standard I2C DDC connection over the AUX channel.
+
+  To model this relationship, DP sinks should be placed as children
+  of the DP controller under the "aux-bus" node.
+
+  At the moment, this binding only handles the eDP case. It is
+  possible it will be extended in the future to handle the DP case.
+  For DP, presumably a connector would be listed under the DP AUX
+  bus instead of a panel.
+
+properties:
+  $nodename:
+    const: "aux-bus"
+
+  panel:
+    $ref: panel/panel-common.yaml#
+
+additionalProperties: false
+
+required:
+  - panel
-- 
2.31.1.818.g46aad6cb9e-goog


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH v8 03/11] dt-bindings: drm/bridge: ti-sn65dsi86: Add aux-bus child
  2021-05-25  0:01 [PATCH v8 00/11] drm: Fix EDID reading on ti-sn65dsi86 by introducing the DP AUX bus Douglas Anderson
  2021-05-25  0:01 ` [PATCH v8 01/11] dt-bindings: display: simple: List hpd properties in panel-simple Douglas Anderson
  2021-05-25  0:01 ` [PATCH v8 02/11] dt-bindings: drm: Introduce the DP AUX bus Douglas Anderson
@ 2021-05-25  0:01 ` Douglas Anderson
  2021-05-28  0:29   ` Linus Walleij
  2021-06-02 18:10   ` Rob Herring
  2021-05-25  0:01 ` [PATCH v8 04/11] dt-bindings: drm/aux-bus: Add an example Douglas Anderson
                   ` (7 subsequent siblings)
  10 siblings, 2 replies; 25+ messages in thread
From: Douglas Anderson @ 2021-05-25  0:01 UTC (permalink / raw)
  To: Andrzej Hajda, Neil Armstrong, Laurent Pinchart, Jonas Karlman,
	Sam Ravnborg
  Cc: robdclark, devicetree, David Airlie, linux-arm-msm,
	Douglas Anderson, Steev Klimaszewski, Bjorn Andersson,
	Stanislav Lisovskiy, Rob Herring, Sandeep Panda, dri-devel,
	Stephen Boyd, Thierry Reding, linux-kernel, Laurent Pinchart

The patch ("dt-bindings: drm: Introduce the DP AUX bus") talks about
how using the DP AUX bus is better than learning how to slice
bread. Let's add it to the ti-sn65dsi86 bindings.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

Changes in v8:
- ti-sn65dsi86 references the new aux bus bindings.

Changes in v7:
- ti-sn65dsi86: Add aux-bus child patch new for v7.

 .../bindings/display/bridge/ti,sn65dsi86.yaml | 20 ++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml
index 26932d2e86ab..4007f36d04ba 100644
--- a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml
+++ b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml
@@ -70,6 +70,9 @@ properties:
     const: 1
     description: See ../../pwm/pwm.yaml for description of the cell formats.
 
+  aux-bus:
+    $ref: ../dp-aux-bus.yaml#
+
   ports:
     $ref: /schemas/graph.yaml#/properties/ports
 
@@ -201,11 +204,26 @@ examples:
 
           port@1 {
             reg = <1>;
-            endpoint {
+            sn65dsi86_out: endpoint {
               remote-endpoint = <&panel_in_edp>;
             };
           };
         };
+
+        aux-bus {
+          panel {
+            compatible = "boe,nv133fhm-n62";
+            power-supply = <&pp3300_dx_edp>;
+            backlight = <&backlight>;
+            hpd-gpios = <&sn65dsi86_bridge 2 GPIO_ACTIVE_HIGH>;
+
+            port {
+              panel_in_edp: endpoint {
+                remote-endpoint = <&sn65dsi86_out>;
+              };
+            };
+          };
+        };
       };
     };
   - |
-- 
2.31.1.818.g46aad6cb9e-goog


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH v8 04/11] dt-bindings: drm/aux-bus: Add an example
  2021-05-25  0:01 [PATCH v8 00/11] drm: Fix EDID reading on ti-sn65dsi86 by introducing the DP AUX bus Douglas Anderson
                   ` (2 preceding siblings ...)
  2021-05-25  0:01 ` [PATCH v8 03/11] dt-bindings: drm/bridge: ti-sn65dsi86: Add aux-bus child Douglas Anderson
@ 2021-05-25  0:01 ` Douglas Anderson
  2021-05-28  0:31   ` Linus Walleij
  2021-06-02 18:16   ` Rob Herring
  2021-05-25  0:01 ` [PATCH v8 05/11] drm: Introduce the DP AUX bus Douglas Anderson
                   ` (6 subsequent siblings)
  10 siblings, 2 replies; 25+ messages in thread
From: Douglas Anderson @ 2021-05-25  0:01 UTC (permalink / raw)
  To: Andrzej Hajda, Neil Armstrong, Laurent Pinchart, Jonas Karlman,
	Sam Ravnborg
  Cc: robdclark, devicetree, David Airlie, linux-arm-msm,
	Douglas Anderson, Steev Klimaszewski, Bjorn Andersson,
	Stanislav Lisovskiy, Rob Herring, dri-devel, Stephen Boyd,
	Thierry Reding, linux-kernel

Now that we have an eDP controller that lists aux-bus, we can safely
add an example to the aux-bus bindings.

NOTE: this example is just a copy of the one in the 'ti-sn65dsi86'
one. It feels useful to have the example in both places simply because
it's important to document the interaction between the two bindings in
both places.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

Changes in v8:
- Separate DP AUX bus binding is new for v8.

 .../bindings/display/dp-aux-bus.yaml          | 65 +++++++++++++++++++
 1 file changed, 65 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/dp-aux-bus.yaml b/Documentation/devicetree/bindings/display/dp-aux-bus.yaml
index 5e4afe9f98fb..43494d2a32a1 100644
--- a/Documentation/devicetree/bindings/display/dp-aux-bus.yaml
+++ b/Documentation/devicetree/bindings/display/dp-aux-bus.yaml
@@ -35,3 +35,68 @@ additionalProperties: false
 
 required:
   - panel
+
+examples:
+  - |
+    #include <dt-bindings/clock/qcom,rpmh.h>
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      bridge@2d {
+        compatible = "ti,sn65dsi86";
+        reg = <0x2d>;
+
+        interrupt-parent = <&tlmm>;
+        interrupts = <10 IRQ_TYPE_LEVEL_HIGH>;
+
+        enable-gpios = <&tlmm 102 GPIO_ACTIVE_HIGH>;
+
+        vpll-supply = <&src_pp1800_s4a>;
+        vccio-supply = <&src_pp1800_s4a>;
+        vcca-supply = <&src_pp1200_l2a>;
+        vcc-supply = <&src_pp1200_l2a>;
+
+        clocks = <&rpmhcc RPMH_LN_BB_CLK2>;
+        clock-names = "refclk";
+
+        no-hpd;
+
+        ports {
+          #address-cells = <1>;
+          #size-cells = <0>;
+
+          port@0 {
+            reg = <0>;
+            endpoint {
+              remote-endpoint = <&dsi0_out>;
+            };
+          };
+
+          port@1 {
+            reg = <1>;
+            sn65dsi86_out: endpoint {
+              remote-endpoint = <&panel_in_edp>;
+            };
+          };
+        };
+
+        aux-bus {
+          panel {
+            compatible = "boe,nv133fhm-n62";
+            power-supply = <&pp3300_dx_edp>;
+            backlight = <&backlight>;
+            hpd-gpios = <&sn65dsi86_bridge 2 GPIO_ACTIVE_HIGH>;
+
+            port {
+              panel_in_edp: endpoint {
+                remote-endpoint = <&sn65dsi86_out>;
+              };
+            };
+          };
+        };
+      };
+    };
-- 
2.31.1.818.g46aad6cb9e-goog


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH v8 05/11] drm: Introduce the DP AUX bus
  2021-05-25  0:01 [PATCH v8 00/11] drm: Fix EDID reading on ti-sn65dsi86 by introducing the DP AUX bus Douglas Anderson
                   ` (3 preceding siblings ...)
  2021-05-25  0:01 ` [PATCH v8 04/11] dt-bindings: drm/aux-bus: Add an example Douglas Anderson
@ 2021-05-25  0:01 ` Douglas Anderson
  2021-05-25  0:01 ` [PATCH v8 06/11] drm/panel: panel-simple: Allow panel-simple be a DP AUX endpoint device Douglas Anderson
                   ` (5 subsequent siblings)
  10 siblings, 0 replies; 25+ messages in thread
From: Douglas Anderson @ 2021-05-25  0:01 UTC (permalink / raw)
  To: Andrzej Hajda, Neil Armstrong, Laurent Pinchart, Jonas Karlman,
	Sam Ravnborg
  Cc: robdclark, Rajeev Nandan, Thomas Zimmermann, David Airlie,
	linux-arm-msm, Douglas Anderson, Steev Klimaszewski,
	Bjorn Andersson, Stanislav Lisovskiy, dri-devel, Stephen Boyd,
	Thierry Reding, linux-kernel, Laurent Pinchart

Historically "simple" eDP panels have been handled by panel-simple
which is a basic platform_device. In the device tree, the panel node
was at the top level and not connected to anything else.

Let's change it so that, instead, panels can be represented as being
children of the "DP AUX bus". Essentially we're saying that the
hierarchy that we're going to represent is the "control" connections
between devices. The DP AUX bus is a control bus provided by an eDP
controller (the parent) and consumed by a device like a panel (the
child).

The primary incentive here is to cleanly provide the panel driver the
ability to communicate over the AUX bus while handling lifetime issues
properly. The panel driver may want the AUX bus for controlling the
backlight or querying the panel's EDID.

The idea for this bus's design was hashed out over IRC [1].

[1] https://people.freedesktop.org/~cbrill/dri-log/?channel=dri-devel&date=2021-05-11

Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Rajeev Nandan <rajeevny@codeaurora.org>
Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
---
There's a whole lot of boilerplate code here. I've tried my best to
grok what all of it should be, drawing inspiration from other similar
bus drivers (auxiliary, i2c, serdev, platform) and I've tried to test
several of the corner cases, but I can't actually believe that I've
touched every code path. Please yell if you see something dumb.

Changes in v8:
- Allow dp-aux-bus to be a module to fix allmodconfig builds

Changes in v7:
- Patch introducing the DP AUX bus is new for v7.

 drivers/gpu/drm/Kconfig          |   5 +
 drivers/gpu/drm/Makefile         |   2 +
 drivers/gpu/drm/drm_dp_aux_bus.c | 326 +++++++++++++++++++++++++++++++
 include/drm/drm_dp_aux_bus.h     |  57 ++++++
 4 files changed, 390 insertions(+)
 create mode 100644 drivers/gpu/drm/drm_dp_aux_bus.c
 create mode 100644 include/drm/drm_dp_aux_bus.h

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index d3a9ca4b1cec..be5c82e55ef6 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -35,6 +35,11 @@ config DRM_MIPI_DSI
 	bool
 	depends on DRM
 
+config DRM_DP_AUX_BUS
+	tristate
+	depends on DRM
+	depends on OF
+
 config DRM_DP_AUX_CHARDEV
 	bool "DRM DP AUX Interface"
 	depends on DRM
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index a91cc7684904..0cff2ad2973b 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -33,6 +33,8 @@ drm-$(CONFIG_PCI) += drm_pci.o
 drm-$(CONFIG_DEBUG_FS) += drm_debugfs.o drm_debugfs_crc.o
 drm-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
 
+obj-$(CONFIG_DRM_DP_AUX_BUS) += drm_dp_aux_bus.o
+
 drm_vram_helper-y := drm_gem_vram_helper.o
 obj-$(CONFIG_DRM_VRAM_HELPER) += drm_vram_helper.o
 
diff --git a/drivers/gpu/drm/drm_dp_aux_bus.c b/drivers/gpu/drm/drm_dp_aux_bus.c
new file mode 100644
index 000000000000..d0e44de287d4
--- /dev/null
+++ b/drivers/gpu/drm/drm_dp_aux_bus.c
@@ -0,0 +1,326 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2021 Google Inc.
+ *
+ * The DP AUX bus is used for devices that are connected over a DisplayPort
+ * AUX bus. The devices on the far side of the bus are referred to as
+ * endpoints in this code.
+ *
+ * Commonly there is only one device connected to the DP AUX bus: a panel.
+ * Though historically panels (even DP panels) have been modeled as simple
+ * platform devices, putting them under the DP AUX bus allows the panel driver
+ * to perform transactions on that bus.
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/pm_domain.h>
+#include <linux/pm_runtime.h>
+
+#include <drm/drm_dp_aux_bus.h>
+#include <drm/drm_dp_helper.h>
+
+
+/**
+ * dp_aux_ep_match() - The match function for the dp_aux_bus.
+ * @dev: The device to match.
+ * @drv: The driver to try to match against.
+ *
+ * At the moment, we just match on device tree.
+ *
+ * Return: True if this driver matches this device; false otherwise.
+ */
+static int dp_aux_ep_match(struct device *dev, struct device_driver *drv)
+{
+	return !!of_match_device(drv->of_match_table, dev);
+}
+
+/**
+ * dp_aux_ep_probe() - The probe function for the dp_aux_bus.
+ * @dev: The device to probe.
+ *
+ * Calls through to the endpoint driver probe.
+ *
+ * Return: 0 if no error or negative error code.
+ */
+static int dp_aux_ep_probe(struct device *dev)
+{
+	struct dp_aux_ep_driver *aux_ep_drv = to_dp_aux_ep_drv(dev->driver);
+	struct dp_aux_ep_device *aux_ep = to_dp_aux_ep_dev(dev);
+	int ret;
+
+	ret = dev_pm_domain_attach(dev, true);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to attach to PM Domain\n");
+
+	ret = aux_ep_drv->probe(aux_ep);
+	if (ret)
+		dev_pm_domain_detach(dev, true);
+
+	return ret;
+}
+
+/**
+ * dp_aux_ep_remove() - The remove function for the dp_aux_bus.
+ * @dev: The device to remove.
+ *
+ * Calls through to the endpoint driver remove.
+ *
+ * Return: 0 if no error or negative error code.
+ */
+static int dp_aux_ep_remove(struct device *dev)
+{
+	struct dp_aux_ep_driver *aux_ep_drv = to_dp_aux_ep_drv(dev->driver);
+	struct dp_aux_ep_device *aux_ep = to_dp_aux_ep_dev(dev);
+
+	if (aux_ep_drv->remove)
+		aux_ep_drv->remove(aux_ep);
+	dev_pm_domain_detach(dev, true);
+
+	return 0;
+}
+
+/**
+ * dp_aux_ep_shutdown() - The shutdown function for the dp_aux_bus.
+ * @dev: The device to shutdown.
+ *
+ * Calls through to the endpoint driver shutdown.
+ */
+static void dp_aux_ep_shutdown(struct device *dev)
+{
+	struct dp_aux_ep_driver *aux_ep_drv;
+
+	if (!dev->driver)
+		return;
+
+	aux_ep_drv = to_dp_aux_ep_drv(dev->driver);
+	if (aux_ep_drv->shutdown)
+		aux_ep_drv->shutdown(to_dp_aux_ep_dev(dev));
+}
+
+static struct bus_type dp_aux_bus_type = {
+	.name		= "dp-aux",
+	.match		= dp_aux_ep_match,
+	.probe		= dp_aux_ep_probe,
+	.remove		= dp_aux_ep_remove,
+	.shutdown	= dp_aux_ep_shutdown,
+};
+
+static ssize_t modalias_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
+{
+	return of_device_modalias(dev, buf, PAGE_SIZE);
+}
+static DEVICE_ATTR_RO(modalias);
+
+static struct attribute *dp_aux_ep_dev_attrs[] = {
+	&dev_attr_modalias.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(dp_aux_ep_dev);
+
+/**
+ * dp_aux_ep_dev_release() - Free memory for the dp_aux_ep device
+ * @dev: The device to free.
+ *
+ * Return: 0 if no error or negative error code.
+ */
+static void dp_aux_ep_dev_release(struct device *dev)
+{
+	kfree(to_dp_aux_ep_dev(dev));
+}
+
+static struct device_type dp_aux_device_type_type = {
+	.groups		= dp_aux_ep_dev_groups,
+	.uevent		= of_device_uevent_modalias,
+	.release	= dp_aux_ep_dev_release,
+};
+
+/**
+ * of_dp_aux_ep_destroy() - Destroy an DP AUX endpoint device
+ * @dev: The device to destroy.
+ * @data: Not used
+ *
+ * This is just used as a callback by of_dp_aux_depopulate_ep_devices() and
+ * is called for _all_ of the child devices of the device providing the AUX bus.
+ * We'll only act on those that are of type "dp_aux_bus_type".
+ *
+ * This function is effectively an inverse of what's in the loop
+ * in of_dp_aux_populate_ep_devices().
+ *
+ * Return: 0 if no error or negative error code.
+ */
+static int of_dp_aux_ep_destroy(struct device *dev, void *data)
+{
+	struct device_node *np = dev->of_node;
+
+	if (dev->bus != &dp_aux_bus_type)
+		return 0;
+
+	if (!of_node_check_flag(np, OF_POPULATED))
+		return 0;
+
+	of_node_clear_flag(np, OF_POPULATED);
+	of_node_put(np);
+
+	device_unregister(dev);
+
+	return 0;
+}
+
+/**
+ * of_dp_aux_depopulate_ep_devices() - Undo of_dp_aux_populate_ep_devices
+ * @aux: The AUX channel whose devices we want to depopulate
+ *
+ * This will destroy all devices that were created
+ * by of_dp_aux_populate_ep_devices().
+ */
+void of_dp_aux_depopulate_ep_devices(struct drm_dp_aux *aux)
+{
+	device_for_each_child_reverse(aux->dev, NULL, of_dp_aux_ep_destroy);
+}
+EXPORT_SYMBOL_GPL(of_dp_aux_depopulate_ep_devices);
+
+/**
+ * of_dp_aux_populate_ep_devices() - Populate the endpoint devices on the DP AUX
+ * @aux: The AUX channel whose devices we want to populate. It is required that
+ *       drm_dp_aux_init() has already been called for this AUX channel.
+ *
+ * This will populate all the devices under the "aux-bus" node of the device
+ * providing the AUX channel (AKA aux->dev).
+ *
+ * When this function finishes, it is _possible_ (but not guaranteed) that
+ * our sub-devices will have finished probing. It should be noted that if our
+ * sub-devices return -EPROBE_DEFER that we will not return any error codes
+ * ourselves but our sub-devices will _not_ have actually probed successfully
+ * yet. There may be other cases (maybe added in the future?) where sub-devices
+ * won't have been probed yet when this function returns, so it's best not to
+ * rely on that.
+ *
+ * If this function succeeds you should later make sure you call
+ * of_dp_aux_depopulate_ep_devices() to undo it, or just use the devm version
+ * of this function.
+ *
+ * Return: 0 if no error or negative error code.
+ */
+int of_dp_aux_populate_ep_devices(struct drm_dp_aux *aux)
+{
+	struct device_node *bus, *np;
+	struct dp_aux_ep_device *aux_ep;
+	int ret;
+
+	/* drm_dp_aux_init() should have been called already; warn if not */
+	WARN_ON_ONCE(!aux->ddc.algo);
+
+	if (!aux->dev->of_node)
+		return 0;
+
+	bus = of_get_child_by_name(aux->dev->of_node, "aux-bus");
+	if (!bus)
+		return 0;
+
+	for_each_available_child_of_node(bus, np) {
+		if (of_node_test_and_set_flag(np, OF_POPULATED))
+			continue;
+
+		aux_ep = kzalloc(sizeof(*aux_ep), GFP_KERNEL);
+		aux_ep->aux = aux;
+
+		aux_ep->dev.parent = aux->dev;
+		aux_ep->dev.bus = &dp_aux_bus_type;
+		aux_ep->dev.type = &dp_aux_device_type_type;
+		aux_ep->dev.of_node = of_node_get(np);
+		dev_set_name(&aux_ep->dev, "aux-%s", dev_name(aux->dev));
+
+		ret = device_register(&aux_ep->dev);
+		if (ret) {
+			dev_err(aux->dev, "Failed to create AUX EP for %pOF: %d\n", np, ret);
+			of_node_clear_flag(np, OF_POPULATED);
+			of_node_put(np);
+
+			/*
+			 * As per docs of device_register(), call this instead
+			 * of kfree() directly for error cases.
+			 */
+			put_device(&aux_ep->dev);
+
+			/*
+			 * Following in the footsteps of of_i2c_register_devices(),
+			 * we won't fail the whole function here--we'll just
+			 * continue registering any other devices we find.
+			 */
+		}
+	}
+
+	of_node_put(bus);
+
+	return 0;
+}
+
+static void of_dp_aux_depopulate_ep_devices_void(void *data)
+{
+	of_dp_aux_depopulate_ep_devices(data);
+}
+
+/**
+ * devm_of_dp_aux_populate_ep_devices() - devm wrapper for of_dp_aux_populate_ep_devices()
+ * @aux: The AUX channel whose devices we want to populate
+ *
+ * Handles freeing w/ devm on the device "aux->dev".
+ *
+ * Return: 0 if no error or negative error code.
+ */
+int devm_of_dp_aux_populate_ep_devices(struct drm_dp_aux *aux)
+{
+	int ret;
+
+	ret = of_dp_aux_populate_ep_devices(aux);
+	if (ret)
+		return ret;
+
+	return devm_add_action_or_reset(aux->dev,
+					of_dp_aux_depopulate_ep_devices_void,
+					aux);
+}
+EXPORT_SYMBOL_GPL(devm_of_dp_aux_populate_ep_devices);
+
+int __dp_aux_dp_driver_register(struct dp_aux_ep_driver *drv, struct module *owner)
+{
+	drv->driver.owner = owner;
+	drv->driver.bus = &dp_aux_bus_type;
+
+	return driver_register(&drv->driver);
+
+}
+EXPORT_SYMBOL_GPL(__dp_aux_dp_driver_register);
+
+void dp_aux_dp_driver_unregister(struct dp_aux_ep_driver *drv)
+{
+	driver_unregister(&drv->driver);
+}
+EXPORT_SYMBOL_GPL(dp_aux_dp_driver_unregister);
+
+static int __init dp_aux_bus_init(void)
+{
+	int ret;
+
+	ret = bus_register(&dp_aux_bus_type);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static void __exit dp_aux_bus_exit(void)
+{
+	bus_unregister(&dp_aux_bus_type);
+}
+
+subsys_initcall(dp_aux_bus_init);
+module_exit(dp_aux_bus_exit);
+
+MODULE_AUTHOR("Douglas Anderson <dianders@chromium.org>");
+MODULE_DESCRIPTION("DRM DisplayPort AUX bus");
+MODULE_LICENSE("GPL v2");
diff --git a/include/drm/drm_dp_aux_bus.h b/include/drm/drm_dp_aux_bus.h
new file mode 100644
index 000000000000..4f19b20b1dd6
--- /dev/null
+++ b/include/drm/drm_dp_aux_bus.h
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright 2021 Google Inc.
+ *
+ * The DP AUX bus is used for devices that are connected over a DisplayPort
+ * AUX bus. The devices on the far side of the bus are referred to as
+ * endpoints in this code.
+ */
+
+#ifndef _DP_AUX_BUS_H_
+#define _DP_AUX_BUS_H_
+
+#include <linux/device.h>
+#include <linux/mod_devicetable.h>
+
+/**
+ * struct dp_aux_ep_device - Main dev structure for DP AUX endpoints
+ *
+ * This is used to instantiate devices that are connected via a DP AUX
+ * bus. Usually the device is a panel, but conceivable other devices could
+ * be hooked up there.
+ */
+struct dp_aux_ep_device {
+	/** @dev: The normal dev pointer */
+	struct device dev;
+	/** @aux: Pointer to the aux bus */
+	struct drm_dp_aux *aux;
+};
+
+struct dp_aux_ep_driver {
+	int (*probe)(struct dp_aux_ep_device *aux_ep);
+	void (*remove)(struct dp_aux_ep_device *aux_ep);
+	void (*shutdown)(struct dp_aux_ep_device *aux_ep);
+	struct device_driver driver;
+};
+
+static inline struct dp_aux_ep_device *to_dp_aux_ep_dev(struct device *dev)
+{
+	return container_of(dev, struct dp_aux_ep_device, dev);
+}
+
+static inline struct dp_aux_ep_driver *to_dp_aux_ep_drv(struct device_driver *drv)
+{
+	return container_of(drv, struct dp_aux_ep_driver, driver);
+}
+
+int of_dp_aux_populate_ep_devices(struct drm_dp_aux *aux);
+void of_dp_aux_depopulate_ep_devices(struct drm_dp_aux *aux);
+int devm_of_dp_aux_populate_ep_devices(struct drm_dp_aux *aux);
+
+#define dp_aux_dp_driver_register(aux_ep_drv) \
+	__dp_aux_dp_driver_register(aux_ep_drv, THIS_MODULE)
+int __dp_aux_dp_driver_register(struct dp_aux_ep_driver *aux_ep_drv,
+				struct module *owner);
+void dp_aux_dp_driver_unregister(struct dp_aux_ep_driver *aux_ep_drv);
+
+#endif /* _DP_AUX_BUS_H_ */
-- 
2.31.1.818.g46aad6cb9e-goog


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH v8 06/11] drm/panel: panel-simple: Allow panel-simple be a DP AUX endpoint device
  2021-05-25  0:01 [PATCH v8 00/11] drm: Fix EDID reading on ti-sn65dsi86 by introducing the DP AUX bus Douglas Anderson
                   ` (4 preceding siblings ...)
  2021-05-25  0:01 ` [PATCH v8 05/11] drm: Introduce the DP AUX bus Douglas Anderson
@ 2021-05-25  0:01 ` Douglas Anderson
  2021-05-25  0:01 ` [PATCH v8 07/11] drm/panel: panel-simple: Stash DP AUX bus; allow using it for DDC Douglas Anderson
                   ` (4 subsequent siblings)
  10 siblings, 0 replies; 25+ messages in thread
From: Douglas Anderson @ 2021-05-25  0:01 UTC (permalink / raw)
  To: Andrzej Hajda, Neil Armstrong, Laurent Pinchart, Jonas Karlman,
	Sam Ravnborg
  Cc: robdclark, David Airlie, linux-arm-msm, Douglas Anderson,
	Steev Klimaszewski, Bjorn Andersson, Stanislav Lisovskiy,
	Thierry Reding, dri-devel, Stephen Boyd, Thierry Reding,
	linux-kernel

The panel-simple driver can already have devices instantiated as
platform devices or MIPI DSI devices. Let's add a 3rd way to
instantiate it: as DP AUX endpoint devices.

At the moment there is no benefit to instantiating it in this way,
but:
- In the next patch we'll give it access to the DDC channel via the DP
  AUX bus.
- Possibly in the future we may use this channel to configure the
  backlight.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Lyude Paul <lyude@redhat.com>
---

(no changes since v7)

Changes in v7:
- Patch to allow panel-simple to be DP AUX EP new for v7.

 drivers/gpu/drm/panel/Kconfig        |  1 +
 drivers/gpu/drm/panel/panel-simple.c | 52 +++++++++++++++++++++++++---
 2 files changed, 49 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
index ef87d92cdf49..b1ea86d9fdaf 100644
--- a/drivers/gpu/drm/panel/Kconfig
+++ b/drivers/gpu/drm/panel/Kconfig
@@ -82,6 +82,7 @@ config DRM_PANEL_SIMPLE
 	depends on BACKLIGHT_CLASS_DEVICE
 	depends on PM
 	select VIDEOMODE_HELPERS
+	select DRM_DP_AUX_BUS
 	help
 	  DRM panel driver for dumb panels that need at most a regulator and
 	  a GPIO to be powered up. Optionally a backlight can be attached so
diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index 21939d4352cf..d3b5ae22d939 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -36,6 +36,7 @@
 
 #include <drm/drm_crtc.h>
 #include <drm/drm_device.h>
+#include <drm/drm_dp_aux_bus.h>
 #include <drm/drm_mipi_dsi.h>
 #include <drm/drm_panel.h>
 
@@ -4957,6 +4958,38 @@ static struct mipi_dsi_driver panel_simple_dsi_driver = {
 	.shutdown = panel_simple_dsi_shutdown,
 };
 
+static int panel_simple_dp_aux_ep_probe(struct dp_aux_ep_device *aux_ep)
+{
+	const struct of_device_id *id;
+
+	id = of_match_node(platform_of_match, aux_ep->dev.of_node);
+	if (!id)
+		return -ENODEV;
+
+	return panel_simple_probe(&aux_ep->dev, id->data);
+}
+
+static void panel_simple_dp_aux_ep_remove(struct dp_aux_ep_device *aux_ep)
+{
+	panel_simple_remove(&aux_ep->dev);
+}
+
+static void panel_simple_dp_aux_ep_shutdown(struct dp_aux_ep_device *aux_ep)
+{
+	panel_simple_shutdown(&aux_ep->dev);
+}
+
+static struct dp_aux_ep_driver panel_simple_dp_aux_ep_driver = {
+	.driver = {
+		.name = "panel-simple-dp-aux",
+		.of_match_table = platform_of_match,	/* Same as platform one! */
+		.pm = &panel_simple_pm_ops,
+	},
+	.probe = panel_simple_dp_aux_ep_probe,
+	.remove = panel_simple_dp_aux_ep_remove,
+	.shutdown = panel_simple_dp_aux_ep_shutdown,
+};
+
 static int __init panel_simple_init(void)
 {
 	int err;
@@ -4965,15 +4998,25 @@ static int __init panel_simple_init(void)
 	if (err < 0)
 		return err;
 
+	err = dp_aux_dp_driver_register(&panel_simple_dp_aux_ep_driver);
+	if (err < 0)
+		goto err_did_platform_register;
+
 	if (IS_ENABLED(CONFIG_DRM_MIPI_DSI)) {
 		err = mipi_dsi_driver_register(&panel_simple_dsi_driver);
-		if (err < 0) {
-			platform_driver_unregister(&panel_simple_platform_driver);
-			return err;
-		}
+		if (err < 0)
+			goto err_did_aux_ep_register;
 	}
 
 	return 0;
+
+err_did_aux_ep_register:
+	dp_aux_dp_driver_unregister(&panel_simple_dp_aux_ep_driver);
+
+err_did_platform_register:
+	platform_driver_unregister(&panel_simple_platform_driver);
+
+	return err;
 }
 module_init(panel_simple_init);
 
@@ -4982,6 +5025,7 @@ static void __exit panel_simple_exit(void)
 	if (IS_ENABLED(CONFIG_DRM_MIPI_DSI))
 		mipi_dsi_driver_unregister(&panel_simple_dsi_driver);
 
+	dp_aux_dp_driver_unregister(&panel_simple_dp_aux_ep_driver);
 	platform_driver_unregister(&panel_simple_platform_driver);
 }
 module_exit(panel_simple_exit);
-- 
2.31.1.818.g46aad6cb9e-goog


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH v8 07/11] drm/panel: panel-simple: Stash DP AUX bus; allow using it for DDC
  2021-05-25  0:01 [PATCH v8 00/11] drm: Fix EDID reading on ti-sn65dsi86 by introducing the DP AUX bus Douglas Anderson
                   ` (5 preceding siblings ...)
  2021-05-25  0:01 ` [PATCH v8 06/11] drm/panel: panel-simple: Allow panel-simple be a DP AUX endpoint device Douglas Anderson
@ 2021-05-25  0:01 ` Douglas Anderson
  2021-06-04 16:10   ` rajeevny
  2021-05-25  0:01 ` [PATCH v8 08/11] drm/bridge: ti-sn65dsi86: Promote the AUX channel to its own sub-dev Douglas Anderson
                   ` (3 subsequent siblings)
  10 siblings, 1 reply; 25+ messages in thread
From: Douglas Anderson @ 2021-05-25  0:01 UTC (permalink / raw)
  To: Andrzej Hajda, Neil Armstrong, Laurent Pinchart, Jonas Karlman,
	Sam Ravnborg
  Cc: robdclark, David Airlie, linux-arm-msm, Douglas Anderson,
	Steev Klimaszewski, Bjorn Andersson, Stanislav Lisovskiy,
	Thierry Reding, dri-devel, Stephen Boyd, Thierry Reding,
	linux-kernel

If panel-simple is instantiated as a DP AUX bus endpoint then we have
access to the DP AUX bus. Let's stash it in the panel-simple
structure, leaving it NULL for the cases where the panel is
instantiated in other ways.

If we happen to have access to the DP AUX bus and we weren't provided
the ddc-i2c-bus in some other manner, let's use the DP AUX bus for it.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Lyude Paul <lyude@redhat.com>
---

(no changes since v7)

Changes in v7:
- Patch using the DP AUX for DDC new for v7.

 drivers/gpu/drm/panel/panel-simple.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index d3b5ae22d939..b09be6e5e147 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -37,6 +37,7 @@
 #include <drm/drm_crtc.h>
 #include <drm/drm_device.h>
 #include <drm/drm_dp_aux_bus.h>
+#include <drm/drm_dp_helper.h>
 #include <drm/drm_mipi_dsi.h>
 #include <drm/drm_panel.h>
 
@@ -186,6 +187,7 @@ struct panel_simple {
 
 	struct regulator *supply;
 	struct i2c_adapter *ddc;
+	struct drm_dp_aux *aux;
 
 	struct gpio_desc *enable_gpio;
 	struct gpio_desc *hpd_gpio;
@@ -658,7 +660,8 @@ static void panel_simple_parse_panel_timing_node(struct device *dev,
 		dev_err(dev, "Reject override mode: No display_timing found\n");
 }
 
-static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
+static int panel_simple_probe(struct device *dev, const struct panel_desc *desc,
+			      struct drm_dp_aux *aux)
 {
 	struct panel_simple *panel;
 	struct display_timing dt;
@@ -674,6 +677,7 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
 	panel->enabled = false;
 	panel->prepared_time = 0;
 	panel->desc = desc;
+	panel->aux = aux;
 
 	panel->no_hpd = of_property_read_bool(dev->of_node, "no-hpd");
 	if (!panel->no_hpd) {
@@ -708,6 +712,8 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
 
 		if (!panel->ddc)
 			return -EPROBE_DEFER;
+	} else if (aux) {
+		panel->ddc = &aux->ddc;
 	}
 
 	if (desc == &panel_dpi) {
@@ -4633,7 +4639,7 @@ static int panel_simple_platform_probe(struct platform_device *pdev)
 	if (!id)
 		return -ENODEV;
 
-	return panel_simple_probe(&pdev->dev, id->data);
+	return panel_simple_probe(&pdev->dev, id->data, NULL);
 }
 
 static int panel_simple_platform_remove(struct platform_device *pdev)
@@ -4913,7 +4919,7 @@ static int panel_simple_dsi_probe(struct mipi_dsi_device *dsi)
 
 	desc = id->data;
 
-	err = panel_simple_probe(&dsi->dev, &desc->desc);
+	err = panel_simple_probe(&dsi->dev, &desc->desc, NULL);
 	if (err < 0)
 		return err;
 
@@ -4966,7 +4972,7 @@ static int panel_simple_dp_aux_ep_probe(struct dp_aux_ep_device *aux_ep)
 	if (!id)
 		return -ENODEV;
 
-	return panel_simple_probe(&aux_ep->dev, id->data);
+	return panel_simple_probe(&aux_ep->dev, id->data, aux_ep->aux);
 }
 
 static void panel_simple_dp_aux_ep_remove(struct dp_aux_ep_device *aux_ep)
-- 
2.31.1.818.g46aad6cb9e-goog


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH v8 08/11] drm/bridge: ti-sn65dsi86: Promote the AUX channel to its own sub-dev
  2021-05-25  0:01 [PATCH v8 00/11] drm: Fix EDID reading on ti-sn65dsi86 by introducing the DP AUX bus Douglas Anderson
                   ` (6 preceding siblings ...)
  2021-05-25  0:01 ` [PATCH v8 07/11] drm/panel: panel-simple: Stash DP AUX bus; allow using it for DDC Douglas Anderson
@ 2021-05-25  0:01 ` Douglas Anderson
  2021-06-06  4:40   ` Bjorn Andersson
  2021-05-25  0:01 ` [PATCH v8 09/11] drm/bridge: ti-sn65dsi86: Add support for the DP AUX bus Douglas Anderson
                   ` (2 subsequent siblings)
  10 siblings, 1 reply; 25+ messages in thread
From: Douglas Anderson @ 2021-05-25  0:01 UTC (permalink / raw)
  To: Andrzej Hajda, Neil Armstrong, Laurent Pinchart, Jonas Karlman,
	Sam Ravnborg
  Cc: robdclark, Jernej Skrabec, David Airlie, linux-arm-msm,
	Douglas Anderson, Steev Klimaszewski, Bjorn Andersson,
	Stanislav Lisovskiy, dri-devel, Stephen Boyd, Thierry Reding,
	linux-kernel, Robert Foss

On its own, this change looks a little strange and doesn't do too much
useful. To understand why we're doing this we need to look forward to
future patches where we're going to probe our panel using the new DP
AUX bus. See the patch ("drm/bridge: ti-sn65dsi86: Add support for the
DP AUX bus").

Let's think about the set of steps we'll want to happen when we have
the DP AUX bus:

1. We'll create the DP AUX bus.
2. We'll populate the devices on the DP AUX bus (AKA our panel).
3. For setting up the bridge-related functions of ti-sn65dsi86 we'll
   need to get a reference to the panel.

If we do #1 - #3 in a single probe call things _mostly_ will work, but
it won't be massively robust. Let's explore.

First let's think of the easy case of no -EPROBE_DEFER. In that case
in step #2 when we populate the devices on the DP AUX bus it will
actually try probing the panel right away. Since the panel probe
doesn't defer then in step #3 we'll get a reference to the panel and
we're golden.

Second, let's think of the case when the panel returns
-EPROBE_DEFER. In that case step #2 won't synchronously create the
panel (it'll just add the device to the defer list to do it
later). Step #3 will fail to get the panel and the bridge sub-device
will return -EPROBE_DEFER. We'll depopulate the DP AUX bus. Later
we'll try the whole sequence again. Presumably the panel will
eventually stop returning -EPROBE_DEFER and we'll go back to the first
case where things were golden. So this case is OK too even if it's a
bit ugly that we have to keep creating / deleting the AUX bus over and
over.

So where is the problem? As I said, it's mostly about robustness. I
don't believe that step #2 (creating the sub-devices) is really
guaranteed to be synchronous. This is evidenced by the fact that it's
allowed to "succeed" by just sticking the device on the deferred
list. If anything about the process changes in Linux as a whole and
step #2 just kicks off the probe of the DP AUX endpoints (our panel)
in the background then we'd be in trouble because we might never get
the panel in step #3.

Adding an extra sub-device means we just don't need to worry about
it. We'll create the sub-device for the DP AUX bus and it won't go
away until the whole ti-sn65dsi86 driver goes away. If the bridge
sub-device defers (maybe because it can't find the panel) that won't
depopulate the DP AUX bus and so we don't need to worry about it.

NOTE: there's a little bit of a trick here. Though the AUX channel can
run without the MIPI-to-eDP bits of the code, the MIPI-to-eDP bits
can't run without the AUX channel. We could come up a complicated
signaling scheme (have the MIPI-to-eDP bits return EPROBE_DEFER for a
while or wait on some sort of completion), but it seems simple enough
to just not even bother creating the bridge device until the AUX
channel probes. That's what we'll do.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Lyude Paul <lyude@redhat.com>
---

(no changes since v7)

Changes in v7:
- Beefed up commit message in context of the DP AUX bus.
- Remove use of now-dropped drm_dp_aux_register_ddc() call.
- Set the proper sub-device "dev" pointer in the AUX structure.

Changes in v6:
- Use new drm_dp_aux_register_ddc() calls.

 drivers/gpu/drm/bridge/ti-sn65dsi86.c | 80 +++++++++++++++++++++++----
 1 file changed, 69 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
index 45a2969afb2b..1ea07d704705 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
@@ -116,6 +116,7 @@
  * struct ti_sn65dsi86 - Platform data for ti-sn65dsi86 driver.
  * @bridge_aux:   AUX-bus sub device for MIPI-to-eDP bridge functionality.
  * @gpio_aux:     AUX-bus sub device for GPIO controller functionality.
+ * @aux_aux:      AUX-bus sub device for eDP AUX channel functionality.
  *
  * @dev:          Pointer to the top level (i2c) device.
  * @regmap:       Regmap for accessing i2c.
@@ -148,6 +149,7 @@
 struct ti_sn65dsi86 {
 	struct auxiliary_device		bridge_aux;
 	struct auxiliary_device		gpio_aux;
+	struct auxiliary_device		aux_aux;
 
 	struct device			*dev;
 	struct regmap			*regmap;
@@ -1333,11 +1335,6 @@ static int ti_sn_bridge_probe(struct auxiliary_device *adev,
 	if (ret)
 		return ret;
 
-	pdata->aux.name = "ti-sn65dsi86-aux";
-	pdata->aux.dev = pdata->dev;
-	pdata->aux.transfer = ti_sn_aux_transfer;
-	drm_dp_aux_init(&pdata->aux);
-
 	pdata->bridge.funcs = &ti_sn_bridge_funcs;
 	pdata->bridge.of_node = np;
 
@@ -1432,6 +1429,53 @@ static int ti_sn65dsi86_add_aux_device(struct ti_sn65dsi86 *pdata,
 	return ret;
 }
 
+static int ti_sn_aux_probe(struct auxiliary_device *adev,
+			   const struct auxiliary_device_id *id)
+{
+	struct ti_sn65dsi86 *pdata = dev_get_drvdata(adev->dev.parent);
+	int ret;
+
+	/*
+	 * We couldn't do this pre-probe because it would confuse pinctrl.
+	 * It would have tried to grab the same pins that the main device had.
+	 * Set it now so that we can put the proper (sub) device in the aux
+	 * structure and it will have the right node.
+	 */
+	adev->dev.of_node = pdata->dev->of_node;
+
+	pdata->aux.name = "ti-sn65dsi86-aux";
+	pdata->aux.dev = &adev->dev;
+	pdata->aux.transfer = ti_sn_aux_transfer;
+	drm_dp_aux_init(&pdata->aux);
+
+	/*
+	 * The eDP to MIPI bridge parts don't work until the AUX channel is
+	 * setup so we don't add it in the main driver probe, we add it now.
+	 */
+	ret = ti_sn65dsi86_add_aux_device(pdata, &pdata->bridge_aux, "bridge");
+
+	/*
+	 * Clear of_node on any errors. Really this only matters if the error
+	 * is -EPROBE_DEFER to avoid (again) keep pinctrl from claiming when
+	 * it tries the probe again, but it shouldn't hurt on any error.
+	 */
+	if (ret)
+		adev->dev.of_node = NULL;
+
+	return ret;
+}
+
+static const struct auxiliary_device_id ti_sn_aux_id_table[] = {
+	{ .name = "ti_sn65dsi86.aux", },
+	{},
+};
+
+static struct auxiliary_driver ti_sn_aux_driver = {
+	.name = "aux",
+	.probe = ti_sn_aux_probe,
+	.id_table = ti_sn_aux_id_table,
+};
+
 static int ti_sn65dsi86_probe(struct i2c_client *client,
 			      const struct i2c_device_id *id)
 {
@@ -1490,10 +1534,11 @@ static int ti_sn65dsi86_probe(struct i2c_client *client,
 	 * motiviation here is to solve the chicken-and-egg problem of probe
 	 * ordering. The bridge wants the panel to be there when it probes.
 	 * The panel wants its HPD GPIO (provided by sn65dsi86 on some boards)
-	 * when it probes. There will soon be other devices (DDC I2C bus, PWM)
-	 * that have the same problem. Having sub-devices allows the some sub
-	 * devices to finish probing even if others return -EPROBE_DEFER and
-	 * gets us around the problems.
+	 * when it probes. The panel and maybe backlight might want the DDC
+	 * bus. Soon the PWM provided by the bridge chip will have the same
+	 * problem. Having sub-devices allows the some sub devices to finish
+	 * probing even if others return -EPROBE_DEFER and gets us around the
+	 * problems.
 	 */
 
 	if (IS_ENABLED(CONFIG_OF_GPIO)) {
@@ -1502,7 +1547,13 @@ static int ti_sn65dsi86_probe(struct i2c_client *client,
 			return ret;
 	}
 
-	return ti_sn65dsi86_add_aux_device(pdata, &pdata->bridge_aux, "bridge");
+	/*
+	 * NOTE: At the end of the AUX channel probe we'll add the aux device
+	 * for the bridge. This is because the bridge can't be used until the
+	 * AUX channel is there and this is a very simple solution to the
+	 * dependency problem.
+	 */
+	return ti_sn65dsi86_add_aux_device(pdata, &pdata->aux_aux, "aux");
 }
 
 static struct i2c_device_id ti_sn65dsi86_id[] = {
@@ -1539,12 +1590,18 @@ static int __init ti_sn65dsi86_init(void)
 	if (ret)
 		goto err_main_was_registered;
 
-	ret = auxiliary_driver_register(&ti_sn_bridge_driver);
+	ret = auxiliary_driver_register(&ti_sn_aux_driver);
 	if (ret)
 		goto err_gpio_was_registered;
 
+	ret = auxiliary_driver_register(&ti_sn_bridge_driver);
+	if (ret)
+		goto err_aux_was_registered;
+
 	return 0;
 
+err_aux_was_registered:
+	auxiliary_driver_unregister(&ti_sn_aux_driver);
 err_gpio_was_registered:
 	ti_sn_gpio_unregister();
 err_main_was_registered:
@@ -1557,6 +1614,7 @@ module_init(ti_sn65dsi86_init);
 static void __exit ti_sn65dsi86_exit(void)
 {
 	auxiliary_driver_unregister(&ti_sn_bridge_driver);
+	auxiliary_driver_unregister(&ti_sn_aux_driver);
 	ti_sn_gpio_unregister();
 	i2c_del_driver(&ti_sn65dsi86_driver);
 }
-- 
2.31.1.818.g46aad6cb9e-goog


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH v8 09/11] drm/bridge: ti-sn65dsi86: Add support for the DP AUX bus
  2021-05-25  0:01 [PATCH v8 00/11] drm: Fix EDID reading on ti-sn65dsi86 by introducing the DP AUX bus Douglas Anderson
                   ` (7 preceding siblings ...)
  2021-05-25  0:01 ` [PATCH v8 08/11] drm/bridge: ti-sn65dsi86: Promote the AUX channel to its own sub-dev Douglas Anderson
@ 2021-05-25  0:01 ` Douglas Anderson
  2021-05-25  0:01 ` [PATCH v8 10/11] drm/bridge: ti-sn65dsi86: Don't read EDID blob over DDC Douglas Anderson
  2021-05-25  0:01 ` [PATCH v8 11/11] arm64: dts: qcom: sc7180-trogdor: Move panel under the bridge chip Douglas Anderson
  10 siblings, 0 replies; 25+ messages in thread
From: Douglas Anderson @ 2021-05-25  0:01 UTC (permalink / raw)
  To: Andrzej Hajda, Neil Armstrong, Laurent Pinchart, Jonas Karlman,
	Sam Ravnborg
  Cc: robdclark, Jernej Skrabec, David Airlie, linux-arm-msm,
	Douglas Anderson, Steev Klimaszewski, Bjorn Andersson,
	Stanislav Lisovskiy, dri-devel, Stephen Boyd, Thierry Reding,
	linux-kernel, Robert Foss

We want to provide our panel with access to the DP AUX channel. The
way to do this is to let our panel be a child of ours using the fancy
new DP AUX bus support.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Lyude Paul <lyude@redhat.com>
---

(no changes since v7)

Changes in v7:
- Patch to support for DP AUX bus on ti-sn65dsi86 new for v7.

 drivers/gpu/drm/bridge/Kconfig        |  1 +
 drivers/gpu/drm/bridge/ti-sn65dsi86.c | 13 +++++++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index 7e7f28eb9546..a82952a85db4 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -292,6 +292,7 @@ config DRM_TI_SN65DSI86
 	select DRM_PANEL
 	select DRM_MIPI_DSI
 	select AUXILIARY_BUS
+	select DRM_DP_AUX_BUS
 	help
 	  Texas Instruments SN65DSI86 DSI to eDP Bridge driver
 
diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
index 1ea07d704705..5263206792f6 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
@@ -23,6 +23,7 @@
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_bridge.h>
+#include <drm/drm_dp_aux_bus.h>
 #include <drm/drm_dp_helper.h>
 #include <drm/drm_mipi_dsi.h>
 #include <drm/drm_of.h>
@@ -1448,19 +1449,27 @@ static int ti_sn_aux_probe(struct auxiliary_device *adev,
 	pdata->aux.transfer = ti_sn_aux_transfer;
 	drm_dp_aux_init(&pdata->aux);
 
+	ret = devm_of_dp_aux_populate_ep_devices(&pdata->aux);
+	if (ret)
+		goto err;
+
 	/*
 	 * The eDP to MIPI bridge parts don't work until the AUX channel is
 	 * setup so we don't add it in the main driver probe, we add it now.
 	 */
 	ret = ti_sn65dsi86_add_aux_device(pdata, &pdata->bridge_aux, "bridge");
 
+	if (ret)
+		goto err;
+
+	return 0;
+err:
 	/*
 	 * Clear of_node on any errors. Really this only matters if the error
 	 * is -EPROBE_DEFER to avoid (again) keep pinctrl from claiming when
 	 * it tries the probe again, but it shouldn't hurt on any error.
 	 */
-	if (ret)
-		adev->dev.of_node = NULL;
+	adev->dev.of_node = NULL;
 
 	return ret;
 }
-- 
2.31.1.818.g46aad6cb9e-goog


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH v8 10/11] drm/bridge: ti-sn65dsi86: Don't read EDID blob over DDC
  2021-05-25  0:01 [PATCH v8 00/11] drm: Fix EDID reading on ti-sn65dsi86 by introducing the DP AUX bus Douglas Anderson
                   ` (8 preceding siblings ...)
  2021-05-25  0:01 ` [PATCH v8 09/11] drm/bridge: ti-sn65dsi86: Add support for the DP AUX bus Douglas Anderson
@ 2021-05-25  0:01 ` Douglas Anderson
  2021-05-25  0:01 ` [PATCH v8 11/11] arm64: dts: qcom: sc7180-trogdor: Move panel under the bridge chip Douglas Anderson
  10 siblings, 0 replies; 25+ messages in thread
From: Douglas Anderson @ 2021-05-25  0:01 UTC (permalink / raw)
  To: Andrzej Hajda, Neil Armstrong, Laurent Pinchart, Jonas Karlman,
	Sam Ravnborg
  Cc: robdclark, Jernej Skrabec, David Airlie, linux-arm-msm,
	Douglas Anderson, Steev Klimaszewski, Bjorn Andersson,
	Stanislav Lisovskiy, dri-devel, Stephen Boyd, Thierry Reding,
	linux-kernel, Robert Foss

This is really just a revert of commit 58074b08c04a ("drm/bridge:
ti-sn65dsi86: Read EDID blob over DDC"), resolving conflicts.

The old code failed to read the EDID properly in a very important
case: before the bridge's pre_enable() was called. The way things need
to work:
1. Read the EDID.
2. Based on the EDID, decide on video settings and pixel clock.
3. Enable the bridge w/ the desired settings.

The way things were working:
1. Try to read the EDID but fail; fall back to hardcoded values.
2. Based on hardcoded values, decide on video settings and pixel clock.
3. Enable the bridge w/ the desired settings.
4. Try again to read the EDID, it works now!
5. Realize that the hardcoded settings weren't quite right.
6. Disable / reenable the bridge w/ the right settings.

The reasons for the failures were twofold:
a) Since we never ran the bridge chip's pre-enable then we never set
   the bit to ignore HPD. This meant the bridge chip didn't even _try_
   to go out on the bus and communicate with the panel.
b) Even if we fixed things to ignore HPD, the EDID still wouldn't read
   if the panel wasn't on.

Instead of reverting the code, we could fix it to set the HPD bit and
also power on the panel. However, it also works nicely to just let the
panel code read the EDID. Now that we've split the driver up we can
expose the DDC AUX channel bus to the panel node. The panel can take
charge of reading the EDID.

NOTE: in order for things to work, anyone that needs to read the EDID
will need to instantiate their panel using the new DP AUX bus (AKA by
listing their panel under the "aux-bus" node of the bridge chip in the
device tree).

In the future if we want to use the bridge chip to provide a full
external DP port (which won't have a panel) then we will have to
conditinally add EDID reading back in.

Suggested-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
---

(no changes since v7)

Changes in v7:
- Adjusted commit message to talk about DP AUX bus.

 drivers/gpu/drm/bridge/ti-sn65dsi86.c | 22 ----------------------
 1 file changed, 22 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
index 5263206792f6..b7453c80cdb8 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
@@ -126,7 +126,6 @@
  * @connector:    Our connector.
  * @host_node:    Remote DSI node.
  * @dsi:          Our MIPI DSI source.
- * @edid:         Detected EDID of eDP panel.
  * @refclk:       Our reference clock.
  * @panel:        Our panel.
  * @enable_gpio:  The GPIO we toggle to enable the bridge.
@@ -157,7 +156,6 @@ struct ti_sn65dsi86 {
 	struct drm_dp_aux		aux;
 	struct drm_bridge		bridge;
 	struct drm_connector		connector;
-	struct edid			*edid;
 	struct device_node		*host_node;
 	struct mipi_dsi_device		*dsi;
 	struct clk			*refclk;
@@ -406,24 +404,6 @@ connector_to_ti_sn65dsi86(struct drm_connector *connector)
 static int ti_sn_bridge_connector_get_modes(struct drm_connector *connector)
 {
 	struct ti_sn65dsi86 *pdata = connector_to_ti_sn65dsi86(connector);
-	struct edid *edid = pdata->edid;
-	int num, ret;
-
-	if (!edid) {
-		pm_runtime_get_sync(pdata->dev);
-		edid = pdata->edid = drm_get_edid(connector, &pdata->aux.ddc);
-		pm_runtime_put_autosuspend(pdata->dev);
-	}
-
-	if (edid && drm_edid_is_valid(edid)) {
-		ret = drm_connector_update_edid_property(connector, edid);
-		if (!ret) {
-			num = drm_add_edid_modes(connector, edid);
-			if (num)
-				return num;
-		}
-	}
-
 	return drm_panel_get_modes(pdata->panel, connector);
 }
 
@@ -1356,8 +1336,6 @@ static void ti_sn_bridge_remove(struct auxiliary_device *adev)
 		mipi_dsi_device_unregister(pdata->dsi);
 	}
 
-	kfree(pdata->edid);
-
 	drm_bridge_remove(&pdata->bridge);
 
 	of_node_put(pdata->host_node);
-- 
2.31.1.818.g46aad6cb9e-goog


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH v8 11/11] arm64: dts: qcom: sc7180-trogdor: Move panel under the bridge chip
  2021-05-25  0:01 [PATCH v8 00/11] drm: Fix EDID reading on ti-sn65dsi86 by introducing the DP AUX bus Douglas Anderson
                   ` (9 preceding siblings ...)
  2021-05-25  0:01 ` [PATCH v8 10/11] drm/bridge: ti-sn65dsi86: Don't read EDID blob over DDC Douglas Anderson
@ 2021-05-25  0:01 ` Douglas Anderson
  10 siblings, 0 replies; 25+ messages in thread
From: Douglas Anderson @ 2021-05-25  0:01 UTC (permalink / raw)
  To: Andrzej Hajda, Neil Armstrong, Laurent Pinchart, Jonas Karlman,
	Sam Ravnborg
  Cc: robdclark, devicetree, linux-arm-msm, Douglas Anderson,
	Steev Klimaszewski, Bjorn Andersson, Stanislav Lisovskiy,
	Rob Herring, Andy Gross, dri-devel, Stephen Boyd, Thierry Reding,
	linux-kernel

Putting the panel under the bridge chip (under the aux-bus node)
allows the panel driver to get access to the DP AUX bus, enabling all
sorts of fabulous new features.

While we're at this, get rid of a level of hierarchy for the panel
node. It doesn't need "ports / port" and can just have a "port" child.

For Linux, this patch has a hard requirement on the patches adding DP
AUX bus support to the ti-sn65dsi86 bridge chip driver. See the patch
("drm/bridge: ti-sn65dsi86: Add support for the DP AUX bus").

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
---

(no changes since v7)

Changes in v7:
- Panel now under bridge chip instead of getting a link to ddc-i2c

 arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi | 30 ++++++++++----------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi b/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi
index 24d293ef56d7..c76afd857b54 100644
--- a/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi
+++ b/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi
@@ -260,21 +260,6 @@ max98357a: audio-codec-0 {
 		#sound-dai-cells = <0>;
 	};
 
-	panel: panel {
-		/* Compatible will be filled in per-board */
-		power-supply = <&pp3300_dx_edp>;
-		backlight = <&backlight>;
-		hpd-gpios = <&sn65dsi86_bridge 2 GPIO_ACTIVE_HIGH>;
-
-		ports {
-			port {
-				panel_in_edp: endpoint {
-					remote-endpoint = <&sn65dsi86_out>;
-				};
-			};
-		};
-	};
-
 	pwmleds {
 		compatible = "pwm-leds";
 		keyboard_backlight: keyboard-backlight {
@@ -674,6 +659,21 @@ sn65dsi86_out: endpoint {
 				};
 			};
 		};
+
+		aux-bus {
+			panel: panel {
+				/* Compatible will be filled in per-board */
+				power-supply = <&pp3300_dx_edp>;
+				backlight = <&backlight>;
+				hpd-gpios = <&sn65dsi86_bridge 2 GPIO_ACTIVE_HIGH>;
+
+				port {
+					panel_in_edp: endpoint {
+						remote-endpoint = <&sn65dsi86_out>;
+					};
+				};
+			};
+		};
 	};
 };
 
-- 
2.31.1.818.g46aad6cb9e-goog


^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH v8 03/11] dt-bindings: drm/bridge: ti-sn65dsi86: Add aux-bus child
  2021-05-25  0:01 ` [PATCH v8 03/11] dt-bindings: drm/bridge: ti-sn65dsi86: Add aux-bus child Douglas Anderson
@ 2021-05-28  0:29   ` Linus Walleij
  2021-06-02 18:06     ` Rob Herring
  2021-06-02 18:10   ` Rob Herring
  1 sibling, 1 reply; 25+ messages in thread
From: Linus Walleij @ 2021-05-28  0:29 UTC (permalink / raw)
  To: Douglas Anderson
  Cc: Rob Clark,
	open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS,
	Jonas Karlman, David Airlie, MSM, open list:DRM PANEL DRIVERS,
	Neil Armstrong, Sandeep Panda, Steev Klimaszewski,
	Bjorn Andersson, Stanislav Lisovskiy, Andrzej Hajda, Rob Herring,
	Laurent Pinchart, Stephen Boyd, Thierry Reding, Sam Ravnborg,
	linux-kernel

On Tue, May 25, 2021 at 2:02 AM Douglas Anderson <dianders@chromium.org> wrote:

> The patch ("dt-bindings: drm: Introduce the DP AUX bus") talks about
> how using the DP AUX bus is better than learning how to slice
> bread. Let's add it to the ti-sn65dsi86 bindings.
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
(...)
>      description: See ../../pwm/pwm.yaml for description of the cell formats.>

Just use the full path:
/schemas/pwm/pwm.yaml

> +  aux-bus:
> +    $ref: ../dp-aux-bus.yaml#

Use the full path. (Same method as above)

This removes the need for ../../... ....

You do it here:

>    ports:
>      $ref: /schemas/graph.yaml#/properties/ports

Other than that I think it looks all right!

Yours,
Linus Walleij

^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH v8 04/11] dt-bindings: drm/aux-bus: Add an example
  2021-05-25  0:01 ` [PATCH v8 04/11] dt-bindings: drm/aux-bus: Add an example Douglas Anderson
@ 2021-05-28  0:31   ` Linus Walleij
  2021-06-02 18:16   ` Rob Herring
  1 sibling, 0 replies; 25+ messages in thread
From: Linus Walleij @ 2021-05-28  0:31 UTC (permalink / raw)
  To: Douglas Anderson
  Cc: Rob Clark,
	open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS,
	Jonas Karlman, David Airlie, MSM, open list:DRM PANEL DRIVERS,
	Neil Armstrong, linux-kernel, Steev Klimaszewski,
	Bjorn Andersson, Stanislav Lisovskiy, Andrzej Hajda, Rob Herring,
	Laurent Pinchart, Stephen Boyd, Thierry Reding, Sam Ravnborg

On Tue, May 25, 2021 at 2:02 AM Douglas Anderson <dianders@chromium.org> wrote:

> Now that we have an eDP controller that lists aux-bus, we can safely
> add an example to the aux-bus bindings.
>
> NOTE: this example is just a copy of the one in the 'ti-sn65dsi86'
> one. It feels useful to have the example in both places simply because
> it's important to document the interaction between the two bindings in
> both places.
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

Looks good.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij

^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH v8 01/11] dt-bindings: display: simple: List hpd properties in panel-simple
  2021-05-25  0:01 ` [PATCH v8 01/11] dt-bindings: display: simple: List hpd properties in panel-simple Douglas Anderson
@ 2021-06-02 18:00   ` Rob Herring
  0 siblings, 0 replies; 25+ messages in thread
From: Rob Herring @ 2021-06-02 18:00 UTC (permalink / raw)
  To: Douglas Anderson
  Cc: Neil Armstrong, David Airlie, dri-devel, Bjorn Andersson,
	Andrzej Hajda, Thierry Reding, Laurent Pinchart, Sam Ravnborg,
	robdclark, Stanislav Lisovskiy, Thierry Reding, devicetree,
	Jonas Karlman, linux-arm-msm, Stephen Boyd, Rob Herring,
	Steev Klimaszewski, linux-kernel

On Mon, 24 May 2021 17:01:49 -0700, Douglas Anderson wrote:
> The HPD (Hot Plug Detect) signal is present in many (probably even
> "most") eDP panels. For eDP, this signal isn't actually used for
> detecting hot-plugs of the panel but is more akin to a "panel ready"
> signal. After you provide power to the panel, panel timing diagrams
> typically say that you should wait for HPD to be asserted (or wait a
> fixed amount of time) before talking to the panel.
> 
> The panel-simple bindings describes many eDP panels and many of these
> panels provide the HPD signal. We should add the HPD-related
> properties to the panel-simple bindings. The HPD properties are
> actually defined in panel-common.yaml, so adding them here just
> documents that they are OK for panels handled by the panel-simple
> bindings.
> 
> NOTE: whether or not we'd include HPD properties in the panel node is
> more a property of the board design than the panel itself. For most
> boards using these eDP panels everything "magically" works without
> specifying any HPD properties and that's been why we haven't needed to
> allow the HPD properties earlier. On these boards the HPD signal goes
> directly to a dedicated "HPD" input to the eDP controller and this
> connection doesn't need to be described in the device tree. The only
> time the HPD properties are needed in the device tree are if HPD is
> hooked up to a GPIO or if HPD is normally on the panel but isn't used
> on a given board. That means that if we don't allow the HPD properties
> in panel-simple then one could argue that we've got to boot all eDP
> panels (or at least all those that someone could conceivably put on a
> system where HPD goes to a GPIO or isn't hooked up) from panel-simple.
> 
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
> 
> Changes in v8:
> - Explain better why HPD needs to be in panel-simple in commit msg.
> 
> Changes in v7:
> - List hpd properties bindings patch new for v7.
> 
>  .../devicetree/bindings/display/panel/panel-simple.yaml         | 2 ++
>  1 file changed, 2 insertions(+)
> 

Reviewed-by: Rob Herring <robh@kernel.org>

^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH v8 03/11] dt-bindings: drm/bridge: ti-sn65dsi86: Add aux-bus child
  2021-05-28  0:29   ` Linus Walleij
@ 2021-06-02 18:06     ` Rob Herring
  2021-06-02 18:09       ` Rob Herring
  0 siblings, 1 reply; 25+ messages in thread
From: Rob Herring @ 2021-06-02 18:06 UTC (permalink / raw)
  To: Linus Walleij
  Cc: Rob Clark,
	open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS,
	Jonas Karlman, David Airlie, MSM, open list:DRM PANEL DRIVERS,
	Neil Armstrong, Douglas Anderson, Steev Klimaszewski,
	Bjorn Andersson, Stanislav Lisovskiy, Andrzej Hajda,
	Sandeep Panda, Laurent Pinchart, Stephen Boyd, Thierry Reding,
	Sam Ravnborg, linux-kernel

On Fri, May 28, 2021 at 02:29:53AM +0200, Linus Walleij wrote:
> On Tue, May 25, 2021 at 2:02 AM Douglas Anderson <dianders@chromium.org> wrote:
> 
> > The patch ("dt-bindings: drm: Introduce the DP AUX bus") talks about
> > how using the DP AUX bus is better than learning how to slice
> > bread. Let's add it to the ti-sn65dsi86 bindings.
> >
> > Signed-off-by: Douglas Anderson <dianders@chromium.org>
> (...)
> >      description: See ../../pwm/pwm.yaml for description of the cell formats.>
> 
> Just use the full path:
> /schemas/pwm/pwm.yaml

Really, just drop it. If we want have generic references and/or 
descriptions for common properties, we should generate that in pretty 
documentation (there are json-schema to doc tools already).

> 
> > +  aux-bus:
> > +    $ref: ../dp-aux-bus.yaml#
> 
> Use the full path. (Same method as above)

+1

> This removes the need for ../../... ....
> 
> You do it here:
> 
> >    ports:
> >      $ref: /schemas/graph.yaml#/properties/ports
> 
> Other than that I think it looks all right!
> 
> Yours,
> Linus Walleij

^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH v8 02/11] dt-bindings: drm: Introduce the DP AUX bus
  2021-05-25  0:01 ` [PATCH v8 02/11] dt-bindings: drm: Introduce the DP AUX bus Douglas Anderson
@ 2021-06-02 18:08   ` Rob Herring
  0 siblings, 0 replies; 25+ messages in thread
From: Rob Herring @ 2021-06-02 18:08 UTC (permalink / raw)
  To: Douglas Anderson
  Cc: robdclark, devicetree, Neil Armstrong, David Airlie,
	linux-arm-msm, Stephen Boyd, Jonas Karlman, linux-kernel,
	dri-devel, Bjorn Andersson, Stanislav Lisovskiy, Andrzej Hajda,
	Rob Herring, Steev Klimaszewski, Thierry Reding, Sam Ravnborg,
	Laurent Pinchart

On Mon, 24 May 2021 17:01:50 -0700, Douglas Anderson wrote:
> We want to be able to list an eDP panel as a child of an eDP
> controller node to represent the fact that the panel is connected to
> the controller's DP AUX bus. Though the panel and the controller are
> connected in several ways, the DP AUX bus is the primary control
> interface between the two and thus makes the most sense to model in
> device tree hierarchy.
> 
> Listing a panel in this way makes it possible for the panel driver to
> easily get access to the DP AUX bus that it resides on, which can be
> useful to help in auto-detecting the panel and for turning on various
> bits.
> 
> NOTE: historically eDP panels were _not_ listed under their controller
> but were listed at the top level of the device tree. This will still
> be supported for backward compatibility (and while DP controller
> drivers are adapted to support the new DT syntax) but should be
> considered deprecated since there is no downside to listing the panel
> under the controller.
> 
> For now, the DP AUX bus bindings will only support an eDP panel
> underneath. It's possible it could be extended to allow having a DP
> connector under it in the future.
> 
> The idea for this bus's design was hashed out over IRC [1].
> 
> [1] https://people.freedesktop.org/~cbrill/dri-log/?channel=dri-devel&date=2021-05-11
> 
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
> My DT yaml-fu is still weak. If I did something stupid, please help me
> learn how to do this better!
> 
> NOTE: there is no "Example" in this bindings file. Yikes! This is
> because I wanted to keep this patch separate from the one that enables
> the first eDP controller. See the patch ("dt-bindings: drm/aux-bus:
> Add an example") for the example.
> 
> ALSO: if anyone else would like to be listed as a "Maintainer" in this
> file then please shout!
> 
> Changes in v8:
> - Separate DP AUX bus binding is new for v8.
> 
>  .../bindings/display/dp-aux-bus.yaml          | 37 +++++++++++++++++++
>  1 file changed, 37 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/dp-aux-bus.yaml
> 

Reviewed-by: Rob Herring <robh@kernel.org>

^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH v8 03/11] dt-bindings: drm/bridge: ti-sn65dsi86: Add aux-bus child
  2021-06-02 18:06     ` Rob Herring
@ 2021-06-02 18:09       ` Rob Herring
  0 siblings, 0 replies; 25+ messages in thread
From: Rob Herring @ 2021-06-02 18:09 UTC (permalink / raw)
  To: Linus Walleij
  Cc: Rob Clark,
	open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS,
	Jonas Karlman, David Airlie, MSM, open list:DRM PANEL DRIVERS,
	Neil Armstrong, Douglas Anderson, Steev Klimaszewski,
	Bjorn Andersson, Stanislav Lisovskiy, Andrzej Hajda,
	Sandeep Panda, Laurent Pinchart, Stephen Boyd, Thierry Reding,
	Sam Ravnborg, linux-kernel

On Wed, Jun 02, 2021 at 01:06:09PM -0500, Rob Herring wrote:
> On Fri, May 28, 2021 at 02:29:53AM +0200, Linus Walleij wrote:
> > On Tue, May 25, 2021 at 2:02 AM Douglas Anderson <dianders@chromium.org> wrote:
> > 
> > > The patch ("dt-bindings: drm: Introduce the DP AUX bus") talks about
> > > how using the DP AUX bus is better than learning how to slice
> > > bread. Let's add it to the ti-sn65dsi86 bindings.
> > >
> > > Signed-off-by: Douglas Anderson <dianders@chromium.org>
> > (...)
> > >      description: See ../../pwm/pwm.yaml for description of the cell formats.>
> > 
> > Just use the full path:
> > /schemas/pwm/pwm.yaml
> 
> Really, just drop it. If we want have generic references and/or 
> descriptions for common properties, we should generate that in pretty 
> documentation (there are json-schema to doc tools already).

Ah, now I see this was just context, so no need for you to fix/change 
this here.

Rob


^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH v8 03/11] dt-bindings: drm/bridge: ti-sn65dsi86: Add aux-bus child
  2021-05-25  0:01 ` [PATCH v8 03/11] dt-bindings: drm/bridge: ti-sn65dsi86: Add aux-bus child Douglas Anderson
  2021-05-28  0:29   ` Linus Walleij
@ 2021-06-02 18:10   ` Rob Herring
  1 sibling, 0 replies; 25+ messages in thread
From: Rob Herring @ 2021-06-02 18:10 UTC (permalink / raw)
  To: Douglas Anderson
  Cc: Neil Armstrong, David Airlie, Sandeep Panda, dri-devel,
	Bjorn Andersson, Andrzej Hajda, Laurent Pinchart, Sam Ravnborg,
	robdclark, Stanislav Lisovskiy, Thierry Reding, devicetree,
	Jonas Karlman, linux-arm-msm, Stephen Boyd, Rob Herring,
	Steev Klimaszewski, linux-kernel

On Mon, 24 May 2021 17:01:51 -0700, Douglas Anderson wrote:
> The patch ("dt-bindings: drm: Introduce the DP AUX bus") talks about
> how using the DP AUX bus is better than learning how to slice
> bread. Let's add it to the ti-sn65dsi86 bindings.
> 
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
> 
> Changes in v8:
> - ti-sn65dsi86 references the new aux bus bindings.
> 
> Changes in v7:
> - ti-sn65dsi86: Add aux-bus child patch new for v7.
> 
>  .../bindings/display/bridge/ti,sn65dsi86.yaml | 20 ++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 

With the path updated,

Reviewed-by: Rob Herring <robh@kernel.org>

^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH v8 04/11] dt-bindings: drm/aux-bus: Add an example
  2021-05-25  0:01 ` [PATCH v8 04/11] dt-bindings: drm/aux-bus: Add an example Douglas Anderson
  2021-05-28  0:31   ` Linus Walleij
@ 2021-06-02 18:16   ` Rob Herring
  2021-06-02 19:55     ` Doug Anderson
  1 sibling, 1 reply; 25+ messages in thread
From: Rob Herring @ 2021-06-02 18:16 UTC (permalink / raw)
  To: Douglas Anderson
  Cc: robdclark, devicetree, dri-devel, Jonas Karlman, David Airlie,
	linux-arm-msm, Neil Armstrong, linux-kernel, Steev Klimaszewski,
	Bjorn Andersson, Stanislav Lisovskiy, Andrzej Hajda,
	Laurent Pinchart, Stephen Boyd, Thierry Reding, Sam Ravnborg

On Mon, May 24, 2021 at 05:01:52PM -0700, Douglas Anderson wrote:
> Now that we have an eDP controller that lists aux-bus, we can safely
> add an example to the aux-bus bindings.
> 
> NOTE: this example is just a copy of the one in the 'ti-sn65dsi86'
> one. It feels useful to have the example in both places simply because
> it's important to document the interaction between the two bindings in
> both places.

Don't forget the 3rd copy that exists in some .dts file most likely. 
That's 3 places to fix when we improve or add some schema.

I've generally been trying to de-duplicate examples...

Rob

^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH v8 04/11] dt-bindings: drm/aux-bus: Add an example
  2021-06-02 18:16   ` Rob Herring
@ 2021-06-02 19:55     ` Doug Anderson
  0 siblings, 0 replies; 25+ messages in thread
From: Doug Anderson @ 2021-06-02 19:55 UTC (permalink / raw)
  To: Rob Herring
  Cc: Rob Clark,
	open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS,
	dri-devel, Jonas Karlman, David Airlie, linux-arm-msm,
	Neil Armstrong, LKML, Steev Klimaszewski, Bjorn Andersson,
	Stanislav Lisovskiy, Andrzej Hajda, Laurent Pinchart,
	Stephen Boyd, Thierry Reding, Sam Ravnborg

Hi,

On Wed, Jun 2, 2021 at 11:16 AM Rob Herring <robh@kernel.org> wrote:
>
> On Mon, May 24, 2021 at 05:01:52PM -0700, Douglas Anderson wrote:
> > Now that we have an eDP controller that lists aux-bus, we can safely
> > add an example to the aux-bus bindings.
> >
> > NOTE: this example is just a copy of the one in the 'ti-sn65dsi86'
> > one. It feels useful to have the example in both places simply because
> > it's important to document the interaction between the two bindings in
> > both places.
>
> Don't forget the 3rd copy that exists in some .dts file most likely.
> That's 3 places to fix when we improve or add some schema.
>
> I've generally been trying to de-duplicate examples...

I'm interpreting your response as: please drop ${SUBJECT} patch from
the series and leave the 'dp-aux-bus.yaml' without any example. The
existing example in the bridge chip is sufficient.

-Doug

^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH v8 07/11] drm/panel: panel-simple: Stash DP AUX bus; allow using it for DDC
  2021-05-25  0:01 ` [PATCH v8 07/11] drm/panel: panel-simple: Stash DP AUX bus; allow using it for DDC Douglas Anderson
@ 2021-06-04 16:10   ` rajeevny
  2021-06-07 17:07     ` Doug Anderson
  0 siblings, 1 reply; 25+ messages in thread
From: rajeevny @ 2021-06-04 16:10 UTC (permalink / raw)
  To: Douglas Anderson
  Cc: robdclark, dri-devel, Jonas Karlman, David Airlie, linux-arm-msm,
	Neil Armstrong, linux-kernel, Steev Klimaszewski,
	Bjorn Andersson, Stanislav Lisovskiy, Andrzej Hajda,
	Thierry Reding, Laurent Pinchart, Stephen Boyd, Thierry Reding,
	Sam Ravnborg

Hi Doug,

>  	panel->no_hpd = of_property_read_bool(dev->of_node, "no-hpd");
>  	if (!panel->no_hpd) {
> @@ -708,6 +712,8 @@ static int panel_simple_probe(struct device *dev,
> const struct panel_desc *desc)
> 
>  		if (!panel->ddc)
>  			return -EPROBE_DEFER;
> +	} else if (aux) {
> +		panel->ddc = &aux->ddc;
>  	}

In panel_simple_probe(), the put_device(&panel->ddc->dev) call is 
causing issue when the aux->ddc is used to assign panel->ddc
It works well when "ddc-i2c-bus" is used to assign panel->ddc

static int panel_simple_probe(...)
{
...

free_ddc:
         if (panel->ddc)
                 put_device(&panel->ddc->dev);

         return err;
}

== Log start ==

[    2.393970] ------------[ cut here ]------------
[    2.398747] kobject: '(null)' ((____ptrval____)): is not initialized, 
yet kobject_put() is being called.
[    2.408554] WARNING: CPU: 7 PID: 7 at lib/kobject.c:752 
kobject_put+0x38/0xe0
...
...
[    2.528574] Call trace:
[    2.531092]  kobject_put+0x38/0xe0
[    2.534594]  put_device+0x20/0x2c
[    2.538002]  panel_simple_probe+0x4bc/0x550
[    2.542300]  panel_simple_dp_aux_ep_probe+0x44/0x5c
[    2.547305]  dp_aux_ep_probe+0x58/0x80

== Log end ==


Sincerely,
Rajeev

^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH v8 08/11] drm/bridge: ti-sn65dsi86: Promote the AUX channel to its own sub-dev
  2021-05-25  0:01 ` [PATCH v8 08/11] drm/bridge: ti-sn65dsi86: Promote the AUX channel to its own sub-dev Douglas Anderson
@ 2021-06-06  4:40   ` Bjorn Andersson
  2021-06-07 17:07     ` Doug Anderson
  0 siblings, 1 reply; 25+ messages in thread
From: Bjorn Andersson @ 2021-06-06  4:40 UTC (permalink / raw)
  To: Douglas Anderson
  Cc: robdclark, Jernej Skrabec, dri-devel, Jonas Karlman,
	David Airlie, linux-arm-msm, Neil Armstrong, linux-kernel,
	Steev Klimaszewski, Stephen Boyd, Stanislav Lisovskiy,
	Andrzej Hajda, Laurent Pinchart, Thierry Reding, Sam Ravnborg,
	Robert Foss

On Mon 24 May 19:01 CDT 2021, Douglas Anderson wrote:

> On its own, this change looks a little strange and doesn't do too much
> useful. To understand why we're doing this we need to look forward to
> future patches where we're going to probe our panel using the new DP
> AUX bus. See the patch ("drm/bridge: ti-sn65dsi86: Add support for the
> DP AUX bus").
> 
> Let's think about the set of steps we'll want to happen when we have
> the DP AUX bus:
> 
> 1. We'll create the DP AUX bus.
> 2. We'll populate the devices on the DP AUX bus (AKA our panel).
> 3. For setting up the bridge-related functions of ti-sn65dsi86 we'll
>    need to get a reference to the panel.
> 
> If we do #1 - #3 in a single probe call things _mostly_ will work, but
> it won't be massively robust. Let's explore.
> 
> First let's think of the easy case of no -EPROBE_DEFER. In that case
> in step #2 when we populate the devices on the DP AUX bus it will
> actually try probing the panel right away. Since the panel probe
> doesn't defer then in step #3 we'll get a reference to the panel and
> we're golden.
> 
> Second, let's think of the case when the panel returns
> -EPROBE_DEFER. In that case step #2 won't synchronously create the
> panel (it'll just add the device to the defer list to do it
> later). Step #3 will fail to get the panel and the bridge sub-device
> will return -EPROBE_DEFER. We'll depopulate the DP AUX bus. Later
> we'll try the whole sequence again. Presumably the panel will
> eventually stop returning -EPROBE_DEFER and we'll go back to the first
> case where things were golden. So this case is OK too even if it's a
> bit ugly that we have to keep creating / deleting the AUX bus over and
> over.
> 
> So where is the problem? As I said, it's mostly about robustness. I
> don't believe that step #2 (creating the sub-devices) is really
> guaranteed to be synchronous. This is evidenced by the fact that it's
> allowed to "succeed" by just sticking the device on the deferred
> list. If anything about the process changes in Linux as a whole and
> step #2 just kicks off the probe of the DP AUX endpoints (our panel)
> in the background then we'd be in trouble because we might never get
> the panel in step #3.
> 
> Adding an extra sub-device means we just don't need to worry about
> it. We'll create the sub-device for the DP AUX bus and it won't go
> away until the whole ti-sn65dsi86 driver goes away. If the bridge
> sub-device defers (maybe because it can't find the panel) that won't
> depopulate the DP AUX bus and so we don't need to worry about it.
> 
> NOTE: there's a little bit of a trick here. Though the AUX channel can
> run without the MIPI-to-eDP bits of the code, the MIPI-to-eDP bits
> can't run without the AUX channel. We could come up a complicated
> signaling scheme (have the MIPI-to-eDP bits return EPROBE_DEFER for a
> while or wait on some sort of completion), but it seems simple enough
> to just not even bother creating the bridge device until the AUX
> channel probes. That's what we'll do.
> 
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> Reviewed-by: Lyude Paul <lyude@redhat.com>
> ---
> 
> (no changes since v7)
> 
> Changes in v7:
> - Beefed up commit message in context of the DP AUX bus.
> - Remove use of now-dropped drm_dp_aux_register_ddc() call.
> - Set the proper sub-device "dev" pointer in the AUX structure.
> 
> Changes in v6:
> - Use new drm_dp_aux_register_ddc() calls.
> 
>  drivers/gpu/drm/bridge/ti-sn65dsi86.c | 80 +++++++++++++++++++++++----
>  1 file changed, 69 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> index 45a2969afb2b..1ea07d704705 100644
> --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> @@ -116,6 +116,7 @@
>   * struct ti_sn65dsi86 - Platform data for ti-sn65dsi86 driver.
>   * @bridge_aux:   AUX-bus sub device for MIPI-to-eDP bridge functionality.
>   * @gpio_aux:     AUX-bus sub device for GPIO controller functionality.
> + * @aux_aux:      AUX-bus sub device for eDP AUX channel functionality.
>   *
>   * @dev:          Pointer to the top level (i2c) device.
>   * @regmap:       Regmap for accessing i2c.
> @@ -148,6 +149,7 @@
>  struct ti_sn65dsi86 {
>  	struct auxiliary_device		bridge_aux;
>  	struct auxiliary_device		gpio_aux;
> +	struct auxiliary_device		aux_aux;
>  
>  	struct device			*dev;
>  	struct regmap			*regmap;
> @@ -1333,11 +1335,6 @@ static int ti_sn_bridge_probe(struct auxiliary_device *adev,
>  	if (ret)
>  		return ret;
>  
> -	pdata->aux.name = "ti-sn65dsi86-aux";
> -	pdata->aux.dev = pdata->dev;
> -	pdata->aux.transfer = ti_sn_aux_transfer;
> -	drm_dp_aux_init(&pdata->aux);
> -
>  	pdata->bridge.funcs = &ti_sn_bridge_funcs;
>  	pdata->bridge.of_node = np;
>  
> @@ -1432,6 +1429,53 @@ static int ti_sn65dsi86_add_aux_device(struct ti_sn65dsi86 *pdata,
>  	return ret;
>  }
>  
> +static int ti_sn_aux_probe(struct auxiliary_device *adev,
> +			   const struct auxiliary_device_id *id)
> +{
> +	struct ti_sn65dsi86 *pdata = dev_get_drvdata(adev->dev.parent);
> +	int ret;
> +
> +	/*
> +	 * We couldn't do this pre-probe because it would confuse pinctrl.
> +	 * It would have tried to grab the same pins that the main device had.
> +	 * Set it now so that we can put the proper (sub) device in the aux
> +	 * structure and it will have the right node.
> +	 */
> +	adev->dev.of_node = pdata->dev->of_node;

I suspect the refcount of the of_node will be wrong here and upon
removing the aux device things will be off...

Instead, I think you're looking for device_set_of_node_from_dev(), which
also sets of_node_reused, which in turn causes pinctrl_bind_pins() to be
skipped - i.e. it seems to deal with the problem your comment describes.

Regards,
Bjorn

^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH v8 07/11] drm/panel: panel-simple: Stash DP AUX bus; allow using it for DDC
  2021-06-04 16:10   ` rajeevny
@ 2021-06-07 17:07     ` Doug Anderson
  0 siblings, 0 replies; 25+ messages in thread
From: Doug Anderson @ 2021-06-07 17:07 UTC (permalink / raw)
  To: Rajeev Nandan
  Cc: Rob Clark, dri-devel, Jonas Karlman, David Airlie, linux-arm-msm,
	Neil Armstrong, LKML, Steev Klimaszewski, Bjorn Andersson,
	Stanislav Lisovskiy, Andrzej Hajda, Thierry Reding,
	Laurent Pinchart, Stephen Boyd, Thierry Reding, Sam Ravnborg

Hi,

On Fri, Jun 4, 2021 at 9:10 AM <rajeevny@codeaurora.org> wrote:
>
> Hi Doug,
>
> >       panel->no_hpd = of_property_read_bool(dev->of_node, "no-hpd");
> >       if (!panel->no_hpd) {
> > @@ -708,6 +712,8 @@ static int panel_simple_probe(struct device *dev,
> > const struct panel_desc *desc)
> >
> >               if (!panel->ddc)
> >                       return -EPROBE_DEFER;
> > +     } else if (aux) {
> > +             panel->ddc = &aux->ddc;
> >       }
>
> In panel_simple_probe(), the put_device(&panel->ddc->dev) call is
> causing issue when the aux->ddc is used to assign panel->ddc
> It works well when "ddc-i2c-bus" is used to assign panel->ddc
>
> static int panel_simple_probe(...)
> {
> ...
>
> free_ddc:
>          if (panel->ddc)
>                  put_device(&panel->ddc->dev);
>
>          return err;
> }

Thanks for catching! Fixed in v9.


-Doug

^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH v8 08/11] drm/bridge: ti-sn65dsi86: Promote the AUX channel to its own sub-dev
  2021-06-06  4:40   ` Bjorn Andersson
@ 2021-06-07 17:07     ` Doug Anderson
  0 siblings, 0 replies; 25+ messages in thread
From: Doug Anderson @ 2021-06-07 17:07 UTC (permalink / raw)
  To: Bjorn Andersson
  Cc: Rob Clark, Jernej Skrabec, dri-devel, Jonas Karlman,
	David Airlie, linux-arm-msm, Neil Armstrong, LKML,
	Steev Klimaszewski, Stephen Boyd, Stanislav Lisovskiy,
	Andrzej Hajda, Laurent Pinchart, Thierry Reding, Sam Ravnborg,
	Robert Foss

Hi,

On Sat, Jun 5, 2021 at 9:40 PM Bjorn Andersson
<bjorn.andersson@linaro.org> wrote:
>
> > +     /*
> > +      * We couldn't do this pre-probe because it would confuse pinctrl.
> > +      * It would have tried to grab the same pins that the main device had.
> > +      * Set it now so that we can put the proper (sub) device in the aux
> > +      * structure and it will have the right node.
> > +      */
> > +     adev->dev.of_node = pdata->dev->of_node;
>
> I suspect the refcount of the of_node will be wrong here and upon
> removing the aux device things will be off...
>
> Instead, I think you're looking for device_set_of_node_from_dev(), which
> also sets of_node_reused, which in turn causes pinctrl_bind_pins() to be
> skipped - i.e. it seems to deal with the problem your comment describes.

You rock! This is exactly what I wanted. I wish I had thought to look
for it--I somehow just assumed that this wasn't already a solved
problem.

-Doug

^ permalink raw reply	[flat|nested] 25+ messages in thread

end of thread, other threads:[~2021-06-07 17:07 UTC | newest]

Thread overview: 25+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-05-25  0:01 [PATCH v8 00/11] drm: Fix EDID reading on ti-sn65dsi86 by introducing the DP AUX bus Douglas Anderson
2021-05-25  0:01 ` [PATCH v8 01/11] dt-bindings: display: simple: List hpd properties in panel-simple Douglas Anderson
2021-06-02 18:00   ` Rob Herring
2021-05-25  0:01 ` [PATCH v8 02/11] dt-bindings: drm: Introduce the DP AUX bus Douglas Anderson
2021-06-02 18:08   ` Rob Herring
2021-05-25  0:01 ` [PATCH v8 03/11] dt-bindings: drm/bridge: ti-sn65dsi86: Add aux-bus child Douglas Anderson
2021-05-28  0:29   ` Linus Walleij
2021-06-02 18:06     ` Rob Herring
2021-06-02 18:09       ` Rob Herring
2021-06-02 18:10   ` Rob Herring
2021-05-25  0:01 ` [PATCH v8 04/11] dt-bindings: drm/aux-bus: Add an example Douglas Anderson
2021-05-28  0:31   ` Linus Walleij
2021-06-02 18:16   ` Rob Herring
2021-06-02 19:55     ` Doug Anderson
2021-05-25  0:01 ` [PATCH v8 05/11] drm: Introduce the DP AUX bus Douglas Anderson
2021-05-25  0:01 ` [PATCH v8 06/11] drm/panel: panel-simple: Allow panel-simple be a DP AUX endpoint device Douglas Anderson
2021-05-25  0:01 ` [PATCH v8 07/11] drm/panel: panel-simple: Stash DP AUX bus; allow using it for DDC Douglas Anderson
2021-06-04 16:10   ` rajeevny
2021-06-07 17:07     ` Doug Anderson
2021-05-25  0:01 ` [PATCH v8 08/11] drm/bridge: ti-sn65dsi86: Promote the AUX channel to its own sub-dev Douglas Anderson
2021-06-06  4:40   ` Bjorn Andersson
2021-06-07 17:07     ` Doug Anderson
2021-05-25  0:01 ` [PATCH v8 09/11] drm/bridge: ti-sn65dsi86: Add support for the DP AUX bus Douglas Anderson
2021-05-25  0:01 ` [PATCH v8 10/11] drm/bridge: ti-sn65dsi86: Don't read EDID blob over DDC Douglas Anderson
2021-05-25  0:01 ` [PATCH v8 11/11] arm64: dts: qcom: sc7180-trogdor: Move panel under the bridge chip Douglas Anderson

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