[PATCH 0/4] Integrate refcounting across of_drm_find_panel() callers

[PATCH 0/4] Integrate refcounting across of_drm_find_panel() callers

[Anusha Srivatsa]

With the panel refcount allocation infrastructure  merged: [1]
and all drivers converted to use the new API: [2],[3] and [4],
the next chunk of work involves integrating refcounting across
different callers across various drivers.

First patch was added to the original series [1] but later
removed. Adding it here with the initial of_drm_find_panel()
callers being updated with refcounting. This is not an exhaustive
list. Remaining drivers to be updated will be sent in next set
of series.

[1] -> https://patchwork.freedesktop.org/series/146750/
[2] -> https://patchwork.freedesktop.org/series/147082/
[3] -> https://patchwork.freedesktop.org/series/147157/
[4] -> https://patchwork.freedesktop.org/series/147246/

Signed-off-by: Anusha Srivatsa <asrivats@redhat.com>
---
Anusha Srivatsa (4):
      drm/panel: get/put panel reference in drm_panel_add/remove()
      drm/panel/samsung-dsicm: Keep up with refcounting
      drm/panel/sun4i: Keep up with refcounting
      drm/panel/exynos: Keep up with refcounting

 drivers/gpu/drm/bridge/samsung-dsim.c   | 1 +
 drivers/gpu/drm/drm_panel.c             | 2 ++
 drivers/gpu/drm/exynos/exynos_drm_dpi.c | 1 +
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c  | 2 ++
 4 files changed, 6 insertions(+)
---
base-commit: 685c407f168cb49a12cc703230d1e2d62767bfd2
change-id: 20250604-of_drm_find_panel_part1-33a2deb79256

Best regards,
-- 
Anusha Srivatsa <asrivats@redhat.com>

[PATCH 1/4] drm/panel: get/put panel reference in drm_panel_add/remove()

[Anusha Srivatsa]

Take the panel reference and put it back as required.
drm_panel_add() and drm_panel_remove() add a panel to
the global registry and removes a panel respectively.
Use get() and put() helpers to keep up with refcounting.

Signed-off-by: Anusha Srivatsa <asrivats@redhat.com>
---
 drivers/gpu/drm/drm_panel.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
index fee65dc65979d6c03753967cefa6d5c4e597277d..ffa3428b5f52c599b53b1fdc0d0a9181a47c91d4 100644
--- a/drivers/gpu/drm/drm_panel.c
+++ b/drivers/gpu/drm/drm_panel.c
@@ -80,6 +80,7 @@ EXPORT_SYMBOL(drm_panel_init);
  */
 void drm_panel_add(struct drm_panel *panel)
 {
+	drm_panel_get(panel);
 	mutex_lock(&panel_lock);
 	list_add_tail(&panel->list, &panel_list);
 	mutex_unlock(&panel_lock);
@@ -97,6 +98,7 @@ void drm_panel_remove(struct drm_panel *panel)
 	mutex_lock(&panel_lock);
 	list_del_init(&panel->list);
 	mutex_unlock(&panel_lock);
+	drm_panel_put(panel);
 }
 EXPORT_SYMBOL(drm_panel_remove);
 

-- 
2.48.1

[PATCH 2/4] drm/panel/samsung-dsicm: Keep up with refcounting

[Anusha Srivatsa]

Put the panel reference back when driver is no
longer using it.

Signed-off-by: Anusha Srivatsa <asrivats@redhat.com>
---
 drivers/gpu/drm/bridge/samsung-dsim.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
index 0014c497e3fe7d8349a119dbdda30d65d816cccf..3667855ff0d6d1b608c579573de657af7fd14388 100644
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -1748,6 +1748,7 @@ static int samsung_dsim_host_attach(struct mipi_dsi_host *host,
 			dsi->out_bridge = ERR_PTR(-EINVAL);
 	}
 
+	drm_panel_put(panel);
 	of_node_put(remote);
 
 	if (IS_ERR(dsi->out_bridge)) {

-- 
2.48.1

Re: [PATCH 2/4] drm/panel/samsung-dsicm: Keep up with refcounting

[Maxime Ripard]

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On Wed, Jun 04, 2025 at 10:45:11PM -0500, Anusha Srivatsa wrote:
> Put the panel reference back when driver is no
> longer using it.
> 
> Signed-off-by: Anusha Srivatsa <asrivats@redhat.com>
> ---
>  drivers/gpu/drm/bridge/samsung-dsim.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
> index 0014c497e3fe7d8349a119dbdda30d65d816cccf..3667855ff0d6d1b608c579573de657af7fd14388 100644
> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> @@ -1748,6 +1748,7 @@ static int samsung_dsim_host_attach(struct mipi_dsi_host *host,
>  			dsi->out_bridge = ERR_PTR(-EINVAL);
>  	}
>  
> +	drm_panel_put(panel);
>  	of_node_put(remote);
>  
>  	if (IS_ERR(dsi->out_bridge)) {

Explaining in your commit log why you think it's a good idea to put it
there would be really nice. In particular, it looks super odd to me that
you would put the panel reference in attach.

Also, your patch doesn't work, and you have a reference inbalance. You
have one taken by the panel driver, put in remove. You have one in
drm_panel_add, put in drm_panel_remove. Which reference do you put here?

This applies to your other patches too.

Maxime

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Re: [PATCH 2/4] drm/panel/samsung-dsicm: Keep up with refcounting

[Maxime Ripard]

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On Mon, Jun 09, 2025 at 10:45:35AM -0500, Anusha Srivatsa wrote:
> On Fri, Jun 6, 2025 at 7:03 AM Maxime Ripard <mripard@kernel.org> wrote:
> 
> > On Wed, Jun 04, 2025 at 10:45:11PM -0500, Anusha Srivatsa wrote:
> > > Put the panel reference back when driver is no
> > > longer using it.
> > >
> > > Signed-off-by: Anusha Srivatsa <asrivats@redhat.com>
> > > ---
> > >  drivers/gpu/drm/bridge/samsung-dsim.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c
> > b/drivers/gpu/drm/bridge/samsung-dsim.c
> > > index
> > 0014c497e3fe7d8349a119dbdda30d65d816cccf..3667855ff0d6d1b608c579573de657af7fd14388
> > 100644
> > > --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> > > +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> > > @@ -1748,6 +1748,7 @@ static int samsung_dsim_host_attach(struct
> > mipi_dsi_host *host,
> > >                       dsi->out_bridge = ERR_PTR(-EINVAL);
> > >       }
> > >
> > > +     drm_panel_put(panel);
> > >       of_node_put(remote);
> > >
> > >       if (IS_ERR(dsi->out_bridge)) {
> >
> > Explaining in your commit log why you think it's a good idea to put it
> > there would be really nice. In particular, it looks super odd to me that
> > you would put the panel reference in attach.
> >
> > Also, your patch doesn't work, and you have a reference inbalance. You
> > have one taken by the panel driver, put in remove. You have one in
> > drm_panel_add, put in drm_panel_remove. Which reference do you put here?
> >
> > This applies to your other patches too.
>
> Yes, I should get the ref in of_drm_find_panel() to put it here. With
> that said, all callers of of_drm_find_panel() should be converted
> instead of the small batch that this series addresses.

Then do the of_drm_find_panel() conversion before, because here you will
free up the structure despite some callers still having a reference on
it.

Maxime

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[PATCH 3/4] drm/panel/sun4i: Keep up with refcounting

[Anusha Srivatsa]

Put the panel reference back when driver is no
longer using it.

Signed-off-by: Anusha Srivatsa <asrivats@redhat.com>
---
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index c35b70d83e53b7397c6e38dde45824bd49fdf099..36d47d7cedde1e1e3e83eb670520664100bd0a25 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -990,6 +990,8 @@ static int sun6i_dsi_detach(struct mipi_dsi_host *host,
 
 	drm_kms_helper_hotplug_event(dsi->drm);
 
+	drm_panel_put(dsi->panel);
+
 	return 0;
 }
 

-- 
2.48.1

[PATCH 4/4] drm/panel/exynos: Keep up with refcounting

[Anusha Srivatsa]

Put the panel reference back when driver is no
longer using it.

Signed-off-by: Anusha Srivatsa <asrivats@redhat.com>
---
 drivers/gpu/drm/exynos/exynos_drm_dpi.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_dpi.c b/drivers/gpu/drm/exynos/exynos_drm_dpi.c
index 0dc36df6ada34cd0d4544f14e616fe3c52dafc73..7b82ff7f2d2761a679fe3b319a73f7d1d4c87033 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_dpi.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_dpi.c
@@ -138,6 +138,7 @@ static void exynos_dpi_disable(struct drm_encoder *encoder)
 		drm_panel_disable(ctx->panel);
 		drm_panel_unprepare(ctx->panel);
 	}
+	drm_panel_put(ctx->panel);
 }
 
 static const struct drm_encoder_helper_funcs exynos_dpi_encoder_helper_funcs = {

-- 
2.48.1