Re: [PATCH v8 07/11] drm/panel: panel-simple: Stash DP AUX bus; allow using it for DDC

[Doug Anderson]

Hi,

On Fri, Jun 4, 2021 at 9:10 AM  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 = >ddc;
> >   }
>
> In panel_simple_probe(), the put_device(>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(>ddc->dev);
>
>  return err;
> }

Thanks for catching! Fixed in v9.


-Doug

Re: [PATCH v8 07/11] drm/panel: panel-simple: Stash DP AUX bus; allow using it for DDC

[rajeevny]

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 = >ddc;
}


In panel_simple_probe(), the put_device(>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(>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

[PATCH v8 07/11] drm/panel: panel-simple: Stash DP AUX bus; allow using it for DDC

[Douglas Anderson]

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 
Reviewed-by: Lyude Paul 
---

(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 
 #include 
 #include 
+#include 
 #include 
 #include 
 
@@ -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 = >ddc;
}
 
if (desc == _dpi) {
@@ -4633,7 +4639,7 @@ static int panel_simple_platform_probe(struct 
platform_device *pdev)
if (!id)
return -ENODEV;
 
-   return panel_simple_probe(>dev, id->data);
+   return panel_simple_probe(>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(>dev, >desc);
+   err = panel_simple_probe(>dev, >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(_ep->dev, id->data);
+   return panel_simple_probe(_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