Re: [PATCH v9 1/3] drm: rockchip: Add basic drm driver

On 10/07/2014 05:56 AM, Mark yao wrote:

On 2014年09月30日 21:31, Andrzej Hajda wrote:

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Hi Mark,

Hi Andrzej,
    Sorry for replying late, I have a vacation before.
    Thanks for your review.

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On 09/30/2014 03:03 PM, Mark Yao wrote:

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From: Mark yao <redacted>

(...)

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+#ifdef CONFIG_PM_SLEEP
+static int rockchip_drm_suspend(struct drm_device *dev, pm_message_t state)
+{
+	struct drm_connector *connector;
+
+	drm_modeset_lock_all(dev);
+	list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
+		int old_dpms = connector->dpms;
+
+		if (connector->funcs->dpms)
+			connector->funcs->dpms(connector, DRM_MODE_DPMS_OFF);
+
+		/* Set the old mode back to the connector for resume */
+		connector->dpms = old_dpms;
+	}
+	drm_modeset_unlock_all(dev);
+
+	return 0;
+}
+
+static int rockchip_drm_resume(struct drm_device *dev)
+{
+	struct drm_connector *connector;
+
+	drm_modeset_lock_all(dev);
+	list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
+		if (connector->funcs->dpms)
+			connector->funcs->dpms(connector, connector->dpms);
+	}
+	drm_modeset_unlock_all(dev);
+
+	drm_helper_resume_force_mode(dev);
+
+	return 0;
+}
+
+static int rockchip_drm_sys_suspend(struct device *dev)
+{
+	struct drm_device *drm_dev = dev_get_drvdata(dev);
+	pm_message_t message;
+
+	if (pm_runtime_suspended(dev))
+		return 0;
+
+	message.event = PM_EVENT_SUSPEND;
+
+	return rockchip_drm_suspend(drm_dev, message);

drm_dev can be NULL here, it can happen when system is suspended
before all components are bound. It can also contain invalid pointer
if after successfull drm initialization de-initialization happens for
some reason.

Some workaround is to check for null here and set drvdata to null on
master unbind. But I guess it should be protected somehow to avoid races
in accessing drvdata.

So, can I use the way that check for null here and set drvdata to null
on master unbind?
I don't know which way is better to protect somehow.

It seems to be a core problem, I have proposed some solution using drm
driver PM callbacks [1]
but it appears these callbacks are obsolete, so different solution
should be found. According to
Russel probably some extension of component framework.
As a temporary solution I guess null checks should work in most cases.

Regards
Andrzej


[1]: https://lkml.org/lkml/2014/10/3/60

-Mark.

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+}
+
+static int rockchip_drm_sys_resume(struct device *dev)
+{
+	struct drm_device *drm_dev = dev_get_drvdata(dev);
+
+	if (!pm_runtime_suspended(dev))
+		return 0;
+
+	return rockchip_drm_resume(drm_dev);

Ditto.

Regards
Andrzej