[PATCH v2 3/4] drm/tegra: dpaux: Restore DP AUX DDC registration order

[Dmitry Osipenko <digetx@xxxxxxxxx>]

Restore DP AUX I2C DDC registration order by moving registration to
DP AUX driver probe phase. 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 to prevent accessing
uninitialized aux->drm_dev. 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 tegra_drm_device() helper
that allows to set aux->drm_dev during DP AUX probe, restoring the DCC
registration order and reviving 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 | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/tegra/dpaux.c b/drivers/gpu/drm/tegra/dpaux.c
index 1f96e416fa08..148d3c00dd8e 100644
--- a/drivers/gpu/drm/tegra/dpaux.c
+++ b/drivers/gpu/drm/tegra/dpaux.c
@@ -530,9 +530,12 @@ static int tegra_dpaux_probe(struct platform_device *pdev)
 	disable_irq(dpaux->irq);
 
 	dpaux->aux.transfer = tegra_dpaux_transfer;
+	dpaux->aux.drm_dev = tegra_drm_device();
 	dpaux->aux.dev = &pdev->dev;
 
-	drm_dp_aux_init(&dpaux->aux);
+	err = drm_dp_aux_register(&dpaux->aux);
+	if (err < 0)
+		goto put_pm;
 
 	/*
 	 * Assume that by default the DPAUX/I2C pads will be used for HDMI,
@@ -544,7 +547,7 @@ static int tegra_dpaux_probe(struct platform_device *pdev)
 	 */
 	err = tegra_dpaux_pad_config(dpaux, DPAUX_PADCTL_FUNC_I2C);
 	if (err < 0)
-		return err;
+		goto dp_aux_unreg;
 
 #ifdef CONFIG_GENERIC_PINCONF
 	dpaux->desc.name = dev_name(&pdev->dev);
@@ -557,7 +560,8 @@ static int tegra_dpaux_probe(struct platform_device *pdev)
 	dpaux->pinctrl = devm_pinctrl_register(&pdev->dev, &dpaux->desc, dpaux);
 	if (IS_ERR(dpaux->pinctrl)) {
 		dev_err(&pdev->dev, "failed to register pincontrol\n");
-		return PTR_ERR(dpaux->pinctrl);
+		err = PTR_ERR(dpaux->pinctrl);
+		goto dp_aux_unreg;
 	}
 #endif
 	/* enable and clear all interrupts */
@@ -571,6 +575,14 @@ static int tegra_dpaux_probe(struct platform_device *pdev)
 	mutex_unlock(&dpaux_lock);
 
 	return 0;
+
+dp_aux_unreg:
+	drm_dp_aux_unregister(&dpaux->aux);
+put_pm:
+	pm_runtime_put_sync(&pdev->dev);
+	pm_runtime_disable(&pdev->dev);
+
+	return err;
 }
 
 static int tegra_dpaux_remove(struct platform_device *pdev)
@@ -579,6 +591,8 @@ static int tegra_dpaux_remove(struct platform_device *pdev)
 
 	cancel_work_sync(&dpaux->work);
 
+	drm_dp_aux_unregister(&dpaux->aux);
+
 	/* make sure pads are powered down when not in use */
 	tegra_dpaux_pad_power_down(dpaux);
 
@@ -717,11 +731,6 @@ int drm_dp_aux_attach(struct drm_dp_aux *aux, struct tegra_output *output)
 	unsigned long timeout;
 	int err;
 
-	aux->drm_dev = output->connector.dev;
-	err = drm_dp_aux_register(aux);
-	if (err < 0)
-		return err;
-
 	output->connector.polled = DRM_CONNECTOR_POLL_HPD;
 	dpaux->output = output;
 
@@ -759,7 +768,6 @@ int drm_dp_aux_detach(struct drm_dp_aux *aux)
 	unsigned long timeout;
 	int err;
 
-	drm_dp_aux_unregister(aux);
 	disable_irq(dpaux->irq);
 
 	if (dpaux->output->panel) {
-- 
2.33.1