From: Thierry Reding <treding@nvidia.com>
Date: Wed, 8 Apr 2020 20:01:00 +0200
Subject: drm/tegra: Properly reference count the DDC I2C adapter

Git-commit: 2340dc15f05f595688ae10f6512cef5ad51476d3
Patch-mainline: v5.10-rc1
References: jsc#SLE-15847

Use the of_get_i2c_adapter_by_node(), which is similar to the existing
call to of_find_i2c_adapter_by_node() except that it also takes a
reference to the owner module of the I2C adapter. In order to properly
balance this out, call i2c_put_adapter() to release the reference to the
I2C adapter and its owner module.

For the special case where the DDC comes from the DPAUX, care must be
taken to perform the same steps (i.e. get_device() and module_get()) so
that the reference counts are all balanced.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
---
 drivers/gpu/drm/tegra/output.c | 4 ++--
 drivers/gpu/drm/tegra/sor.c    | 7 ++++++-
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/tegra/output.c b/drivers/gpu/drm/tegra/output.c
index e36e5e7c2f69..03382550f7d9 100644
--- a/drivers/gpu/drm/tegra/output.c
+++ b/drivers/gpu/drm/tegra/output.c
@@ -112,7 +112,7 @@ int tegra_output_probe(struct tegra_output *output)
 
 	ddc = of_parse_phandle(output->of_node, "nvidia,ddc-i2c-bus", 0);
 	if (ddc) {
-		output->ddc = of_find_i2c_adapter_by_node(ddc);
+		output->ddc = of_get_i2c_adapter_by_node(ddc);
 		if (!output->ddc) {
 			err = -EPROBE_DEFER;
 			of_node_put(ddc);
@@ -173,7 +173,7 @@ void tegra_output_remove(struct tegra_output *output)
 		free_irq(output->hpd_irq, output);
 
 	if (output->ddc)
-		put_device(&output->ddc->dev);
+		i2c_put_adapter(output->ddc);
 }
 
 int tegra_output_init(struct drm_device *drm, struct tegra_output *output)
diff --git a/drivers/gpu/drm/tegra/sor.c b/drivers/gpu/drm/tegra/sor.c
index 45b5258c77a2..e88a17c2937f 100644
--- a/drivers/gpu/drm/tegra/sor.c
+++ b/drivers/gpu/drm/tegra/sor.c
@@ -3728,7 +3728,12 @@ static int tegra_sor_probe(struct platform_device *pdev)
 		if (!sor->aux)
 			return -EPROBE_DEFER;
 
-		sor->output.ddc = &sor->aux->ddc;
+		if (get_device(&sor->aux->ddc.dev)) {
+			if (try_module_get(sor->aux->ddc.owner))
+				sor->output.ddc = &sor->aux->ddc;
+			else
+				put_device(&sor->aux->ddc.dev);
+		}
 	}
 
 	if (!sor->aux) {
-- 
2.26.2