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drm/tegra: Fix crash caused by reference count imbalance
Commitd2307dea14
("drm/atomic: use connector references (v3)") added reference counting for DRM connectors and this caused a crash when exercising system suspend on Tegra114 Dalmore. The Tegra DSI driver implements a Tegra specific function, tegra_dsi_connector_duplicate_state(), to duplicate the connector state and destroys the state using the generic helper function, drm_atomic_helper_connector_destroy_state(). Following commitd2307dea14
("drm/atomic: use connector references (v3)") there is now an imbalance in the connector reference count because the Tegra function to duplicate state does not take a reference when duplicating the state information. However, the generic helper function to destroy the state information assumes a reference has been taken and during system suspend, when the connector state is destroyed, this leads to a crash because we attempt to put the reference for an object that has already been freed. Fix this by calling __drm_atomic_helper_connector_duplicate_state() from tegra_dsi_connector_duplicate_state() to ensure that we take a reference on a connector if crtc is set. Note that this will also copy the connector state a 2nd time, but this should be harmless. By fixing tegra_dsi_connector_duplicate_state() to take a reference, although a crash was no longer seen, it was then observed that after each system suspend-resume cycle, the reference would be one greater than before the suspend-resume cycle. Following commitd2307dea14
("drm/atomic: use connector references (v3)"), it was found that we also need to put the reference when calling the function tegra_dsi_connector_reset() before freeing the state. Fix this by updating tegra_dsi_connector_reset() to call the function __drm_atomic_helper_connector_destroy_state() in order to put the reference for the connector. Fixes:d2307dea14
("drm/atomic: use connector references (v3)") Signed-off-by: Jon Hunter <jonathanh@nvidia.com> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Acked-by: Thierry Reding <treding@nvidia.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/1463585856-16606-1-git-send-email-jonathanh@nvidia.com
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@ -745,13 +745,17 @@ static void tegra_dsi_soft_reset(struct tegra_dsi *dsi)
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static void tegra_dsi_connector_reset(struct drm_connector *connector)
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{
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struct tegra_dsi_state *state =
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kzalloc(sizeof(*state), GFP_KERNEL);
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struct tegra_dsi_state *state = kzalloc(sizeof(*state), GFP_KERNEL);
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if (state) {
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if (!state)
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return;
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if (connector->state) {
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__drm_atomic_helper_connector_destroy_state(connector->state);
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kfree(connector->state);
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__drm_atomic_helper_connector_reset(connector, &state->base);
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}
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__drm_atomic_helper_connector_reset(connector, &state->base);
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}
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static struct drm_connector_state *
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@ -764,6 +768,9 @@ tegra_dsi_connector_duplicate_state(struct drm_connector *connector)
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if (!copy)
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return NULL;
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__drm_atomic_helper_connector_duplicate_state(connector,
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©->base);
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return ©->base;
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}
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