[PATCH] drm/probe-helpers: Drop locking from poll_enable
Daniel Vetter
daniel.vetter at ffwll.ch
Wed Jan 11 09:01:17 UTC 2017
It was only needed to protect the connector_list walking, see
commit 8c4ccc4ab6f64e859d4ff8d7c02c2ed2e956e07f
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date: Thu Jul 9 23:44:26 2015 +0200
drm/probe-helper: Grab mode_config.mutex in poll_init/enable
Unfortunately the commit message of that patch fails to mention that
the new locking check was for the connector_list.
But that requirement disappeared in
commit c36a3254f7857f1ad9badbe3578ccc92be541a8e
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date: Thu Dec 15 16:58:43 2016 +0100
drm: Convert all helpers to drm_connector_list_iter
and so we can drop this again.
This fixes a locking inversion on nouveau, where the rpm code needs to
re-enable. But in other places the rpm_get() calls are nested within
the big modeset locks.
While at it, also improve the kerneldoc for these two functions a
notch.
v2: Update the kerneldoc even more to explain that these functions
can't be called concurrently, or bad things happen (Chris).
Cc: Dave Airlie <airlied at gmail.com>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
drivers/gpu/drm/drm_probe_helper.c | 51 ++++++++++++++----------------------
drivers/gpu/drm/i915/intel_hotplug.c | 4 +--
include/drm/drm_crtc_helper.h | 1 -
3 files changed, 22 insertions(+), 34 deletions(-)
diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index 20f48d1e2785..93381454bdf7 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -115,25 +115,28 @@ static int drm_helper_probe_add_cmdline_mode(struct drm_connector *connector)
#define DRM_OUTPUT_POLL_PERIOD (10*HZ)
/**
- * drm_kms_helper_poll_enable_locked - re-enable output polling.
+ * drm_kms_helper_poll_enable - re-enable output polling.
* @dev: drm_device
*
- * This function re-enables the output polling work without
- * locking the mode_config mutex.
+ * This function re-enables the output polling work, after it has been
+ * temporarily disabled using drm_kms_helper_poll_disable(), for example over
+ * suspend/resume.
*
- * This is like drm_kms_helper_poll_enable() however it is to be
- * called from a context where the mode_config mutex is locked
- * already.
+ * Drivers can call this helper from their device resume implementation. It is
+ * an error to call this when the output polling support has not yet been set
+ * up.
+ *
+ * Note that calls to enable and disable polling must be strictly ordered, which
+ * is automatically the case when they're only call from suspend/resume
+ * callbacks.
*/
-void drm_kms_helper_poll_enable_locked(struct drm_device *dev)
+void drm_kms_helper_poll_enable(struct drm_device *dev)
{
bool poll = false;
struct drm_connector *connector;
struct drm_connector_list_iter conn_iter;
unsigned long delay = DRM_OUTPUT_POLL_PERIOD;
- WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
-
if (!dev->mode_config.poll_enabled || !drm_kms_helper_poll)
return;
@@ -163,7 +166,7 @@ void drm_kms_helper_poll_enable_locked(struct drm_device *dev)
if (poll)
schedule_delayed_work(&dev->mode_config.output_poll_work, delay);
}
-EXPORT_SYMBOL(drm_kms_helper_poll_enable_locked);
+EXPORT_SYMBOL(drm_kms_helper_poll_enable);
static enum drm_connector_status
drm_connector_detect(struct drm_connector *connector, bool force)
@@ -290,7 +293,7 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
/* Re-enable polling in case the global poll config changed. */
if (drm_kms_helper_poll != dev->mode_config.poll_running)
- drm_kms_helper_poll_enable_locked(dev);
+ drm_kms_helper_poll_enable(dev);
dev->mode_config.poll_running = drm_kms_helper_poll;
@@ -484,8 +487,12 @@ static void output_poll_execute(struct work_struct *work)
* This function disables the output polling work.
*
* Drivers can call this helper from their device suspend implementation. It is
- * not an error to call this even when output polling isn't enabled or arlready
- * disabled.
+ * not an error to call this even when output polling isn't enabled or already
+ * disabled. Polling is re-enabled by calling drm_kms_helper_poll_enable().
+ *
+ * Note that calls to enable and disable polling must be strictly ordered, which
+ * is automatically the case when they're only call from suspend/resume
+ * callbacks.
*/
void drm_kms_helper_poll_disable(struct drm_device *dev)
{
@@ -496,24 +503,6 @@ void drm_kms_helper_poll_disable(struct drm_device *dev)
EXPORT_SYMBOL(drm_kms_helper_poll_disable);
/**
- * drm_kms_helper_poll_enable - re-enable output polling.
- * @dev: drm_device
- *
- * This function re-enables the output polling work.
- *
- * Drivers can call this helper from their device resume implementation. It is
- * an error to call this when the output polling support has not yet been set
- * up.
- */
-void drm_kms_helper_poll_enable(struct drm_device *dev)
-{
- mutex_lock(&dev->mode_config.mutex);
- drm_kms_helper_poll_enable_locked(dev);
- mutex_unlock(&dev->mode_config.mutex);
-}
-EXPORT_SYMBOL(drm_kms_helper_poll_enable);
-
-/**
* drm_kms_helper_poll_init - initialize and enable output polling
* @dev: drm_device
*
diff --git a/drivers/gpu/drm/i915/intel_hotplug.c b/drivers/gpu/drm/i915/intel_hotplug.c
index 2ddc9e5842ec..5122d4bfb70e 100644
--- a/drivers/gpu/drm/i915/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/intel_hotplug.c
@@ -182,7 +182,7 @@ static void intel_hpd_irq_storm_disable(struct drm_i915_private *dev_priv)
/* Enable polling and queue hotplug re-enabling. */
if (hpd_disabled) {
- drm_kms_helper_poll_enable_locked(dev);
+ drm_kms_helper_poll_enable(dev);
mod_delayed_work(system_wq, &dev_priv->hotplug.reenable_work,
msecs_to_jiffies(HPD_STORM_REENABLE_DELAY));
}
@@ -519,7 +519,7 @@ static void i915_hpd_poll_init_work(struct work_struct *work)
drm_connector_list_iter_put(&conn_iter);
if (enabled)
- drm_kms_helper_poll_enable_locked(dev);
+ drm_kms_helper_poll_enable(dev);
mutex_unlock(&dev->mode_config.mutex);
diff --git a/include/drm/drm_crtc_helper.h b/include/drm/drm_crtc_helper.h
index 982c299e435a..d026f5017c33 100644
--- a/include/drm/drm_crtc_helper.h
+++ b/include/drm/drm_crtc_helper.h
@@ -73,6 +73,5 @@ extern void drm_kms_helper_hotplug_event(struct drm_device *dev);
extern void drm_kms_helper_poll_disable(struct drm_device *dev);
extern void drm_kms_helper_poll_enable(struct drm_device *dev);
-extern void drm_kms_helper_poll_enable_locked(struct drm_device *dev);
#endif
--
2.11.0
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