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From:   Lyude Paul <lyude@redhat.com>
To:     nouveau@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        amd-gfx@lists.freedesktop.org, intel-gfx@lists.freedesktop.org
Cc:     Thierry Reding <thierry.reding@gmail.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        linux-tegra@vger.kernel.org (open list:DRM DRIVERS FOR NVIDIA TEGRA),
        linux-kernel@vger.kernel.org (open list)
Subject: [PATCH v2 02/20] drm/tegra: Don't register DP AUX channels before connectors
Date:   Fri, 26 Mar 2021 16:37:49 -0400
Message-Id: <20210326203807.105754-3-lyude@redhat.com>
In-Reply-To: <20210326203807.105754-1-lyude@redhat.com>
References: <20210326203807.105754-1-lyude@redhat.com>
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As pointed out by the documentation for drm_dp_aux_register(),
drm_dp_aux_init() should be used in situations where the AUX channel for a
display driver can potentially be registered before it's respective DRM
driver. This is the case with Tegra, since the DP aux channel exists as a
platform device instead of being a grandchild of the DRM device.

Since we're about to add a backpointer to a DP AUX channel's respective DRM
device, let's fix this so that we don't potentially allow userspace to use
the AUX channel before we've associated it with it's DRM connector.

Signed-off-by: Lyude Paul <lyude@redhat.com>
---
 drivers/gpu/drm/tegra/dpaux.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/tegra/dpaux.c b/drivers/gpu/drm/tegra/dpaux.c
index 105fb9cdbb3b..ea56c6ec25e4 100644
--- a/drivers/gpu/drm/tegra/dpaux.c
+++ b/drivers/gpu/drm/tegra/dpaux.c
@@ -534,9 +534,7 @@ static int tegra_dpaux_probe(struct platform_device *pdev)
 	dpaux->aux.transfer = tegra_dpaux_transfer;
 	dpaux->aux.dev = &pdev->dev;
 
-	err = drm_dp_aux_register(&dpaux->aux);
-	if (err < 0)
-		return err;
+	drm_dp_aux_init(&dpaux->aux);
 
 	/*
 	 * Assume that by default the DPAUX/I2C pads will be used for HDMI,
@@ -589,8 +587,6 @@ static int tegra_dpaux_remove(struct platform_device *pdev)
 	pm_runtime_put_sync(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
 
-	drm_dp_aux_unregister(&dpaux->aux);
-
 	mutex_lock(&dpaux_lock);
 	list_del(&dpaux->list);
 	mutex_unlock(&dpaux_lock);
@@ -723,6 +719,10 @@ int drm_dp_aux_attach(struct drm_dp_aux *aux, struct tegra_output *output)
 	unsigned long timeout;
 	int err;
 
+	err = drm_dp_aux_register(aux);
+	if (err < 0)
+		return err;
+
 	output->connector.polled = DRM_CONNECTOR_POLL_HPD;
 	dpaux->output = output;
 
@@ -760,6 +760,7 @@ 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) {
-- 
2.30.2