Turning on an i2c-hid device can be a slow process. This is why
i2c-hid devices use PROBE_PREFER_ASYNCHRONOUS. Unfortunately, when
we're a panel follower the i2c-hid power up sequence now blocks the
power on of the panel. Let's fix that by scheduling the work on the
system_wq.
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
---
(no changes since v2)
Changes in v2:
- ihid_core_panel_prepare_work() is now static.
- Improve documentation for smp_wmb().
drivers/hid/i2c-hid/i2c-hid-core.c | 50 +++++++++++++++++++++++++++---
1 file changed, 46 insertions(+), 4 deletions(-)
diff --git a/drivers/hid/i2c-hid/i2c-hid-core.c b/drivers/hid/i2c-hid/i2c-hid-core.c
index fa6d1f624342..6940e74d8acb 100644
--- a/drivers/hid/i2c-hid/i2c-hid-core.c
+++ b/drivers/hid/i2c-hid/i2c-hid-core.c
@@ -110,7 +110,9 @@ struct i2c_hid {
struct i2chid_ops *ops;
struct drm_panel_follower panel_follower;
+ struct work_struct panel_follower_prepare_work;
bool is_panel_follower;
+ bool prepare_work_finished;
};
static const struct i2c_hid_quirks {
@@ -1062,10 +1064,12 @@ static int i2c_hid_core_initial_power_up(struct i2c_hid *ihid)
return ret;
}
-static int i2c_hid_core_panel_prepared(struct drm_panel_follower *follower)
+static void ihid_core_panel_prepare_work(struct work_struct *work)
{
- struct i2c_hid *ihid = container_of(follower, struct i2c_hid, panel_follower);
+ struct i2c_hid *ihid = container_of(work, struct i2c_hid,
+ panel_follower_prepare_work);
struct hid_device *hid = ihid->hid;
+ int ret;
/*
* hid->version is set on the first power up. If it's still zero then
@@ -1073,15 +1077,52 @@ static int i2c_hid_core_panel_prepared(struct drm_panel_follower *follower)
* steps.
*/
if (!hid->version)
- return i2c_hid_core_initial_power_up(ihid);
+ ret = i2c_hid_core_initial_power_up(ihid);
+ else
+ ret = i2c_hid_core_resume(ihid);
- return i2c_hid_core_resume(ihid);
+ if (ret)
+ dev_warn(&ihid->client->dev, "Power on failed: %d\n", ret);
+ else
+ WRITE_ONCE(ihid->prepare_work_finished, true);
+
+ /*
+ * The work APIs provide a number of memory ordering guarantees
+ * including one that says that memory writes before schedule_work()
+ * are always visible to the work function, but they don't appear to
+ * guarantee that a write that happened in the work is visible after
+ * cancel_work_sync(). We'll add a write memory barrier here to match
+ * with i2c_hid_core_panel_unpreparing() to ensure that our write to
+ * prepare_work_finished is visible there.
+ */
+ smp_wmb();
+}
+
+static int i2c_hid_core_panel_prepared(struct drm_panel_follower *follower)
+{
+ struct i2c_hid *ihid = container_of(follower, struct i2c_hid, panel_follower);
+
+ /*
+ * Powering on a touchscreen can be a slow process. Queue the work to
+ * the system workqueue so we don't block the panel's power up.
+ */
+ WRITE_ONCE(ihid->prepare_work_finished, false);
+ schedule_work(&ihid->panel_follower_prepare_work);
+
+ return 0;
}
static int i2c_hid_core_panel_unpreparing(struct drm_panel_follower *follower)
{
struct i2c_hid *ihid = container_of(follower, struct i2c_hid, panel_follower);
+ cancel_work_sync(&ihid->panel_follower_prepare_work);
+
+ /* Match with ihid_core_panel_prepare_work() */
+ smp_rmb();
+ if (!READ_ONCE(ihid->prepare_work_finished))
+ return 0;
+
return i2c_hid_core_suspend(ihid);
}
@@ -1149,6 +1190,7 @@ int i2c_hid_core_probe(struct i2c_client *client, struct i2chid_ops *ops,
init_waitqueue_head(&ihid->wait);
mutex_init(&ihid->reset_lock);
+ INIT_WORK(&ihid->panel_follower_prepare_work, ihid_core_panel_prepare_work);
/* we need to allocate the command buffer without knowing the maximum
* size of the reports. Let's use HID_MIN_BUFFER_SIZE, then we do the
--
2.41.0.487.g6d72f3e995-goog
