[PATCH v1 2/2] drm/tegra: Use drm_dp_aux_register_ddc/chardev() helpers

[Dmitry Osipenko]

Use drm_dp_aux_register_ddc/chardev() helpers that allow to register I2C
adapter separately from the character device. This fixes broken display
panel driver of Acer Chromebook CB5-311 that fails to probe starting with
v5.13 kernel when DP AUX registration order was changed. Tegra SOR driver
is never probed now using the new registration order because tegra-output
always fails with -EPROBE_DEFER due to missing display panel that requires
DP AUX DDC to be registered first. The offending commit made DDC to be
registered after SOR's output, which can't ever happen. Use new helpers
to restore the registration order and revive display panel.

Cc: <stable@xxxxxxxxxxxxxxx> # 5.13+
Fixes: 39c17ae60ea9 ("drm/tegra: Don't register DP AUX channels before connectors")
Reported-by: Thomas Graichen <thomas.graichen@xxxxxxxxx> # T124 Nyan Big
Tested-by: Thomas Graichen <thomas.graichen@xxxxxxxxx> # T124 Nyan Big
Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
---
 drivers/gpu/drm/tegra/dpaux.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/tegra/dpaux.c b/drivers/gpu/drm/tegra/dpaux.c
index 1f96e416fa08..e0d675c7c2e5 100644
--- a/drivers/gpu/drm/tegra/dpaux.c
+++ b/drivers/gpu/drm/tegra/dpaux.c
@@ -532,7 +532,9 @@ static int tegra_dpaux_probe(struct platform_device *pdev)
 	dpaux->aux.transfer = tegra_dpaux_transfer;
 	dpaux->aux.dev = &pdev->dev;
 
-	drm_dp_aux_init(&dpaux->aux);
+	err = drm_dp_aux_register_ddc(&dpaux->aux);
+	if (err < 0)
+		return err;
 
 	/*
 	 * Assume that by default the DPAUX/I2C pads will be used for HDMI,
@@ -585,6 +587,8 @@ static int tegra_dpaux_remove(struct platform_device *pdev)
 	pm_runtime_put_sync(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
 
+	drm_dp_aux_unregister_ddc(&dpaux->aux);
+
 	mutex_lock(&dpaux_lock);
 	list_del(&dpaux->list);
 	mutex_unlock(&dpaux_lock);
@@ -718,7 +722,7 @@ int drm_dp_aux_attach(struct drm_dp_aux *aux, struct tegra_output *output)
 	int err;
 
 	aux->drm_dev = output->connector.dev;
-	err = drm_dp_aux_register(aux);
+	err = drm_dp_aux_register_chardev(aux);
 	if (err < 0)
 		return err;
 
@@ -759,7 +763,7 @@ int drm_dp_aux_detach(struct drm_dp_aux *aux)
 	unsigned long timeout;
 	int err;
 
-	drm_dp_aux_unregister(aux);
+	drm_dp_aux_unregister_chardev(aux);
 	disable_irq(dpaux->irq);
 
 	if (dpaux->output->panel) {
-- 
2.33.1