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From:   Douglas Anderson <dianders@chromium.org>
To:     Jiri Kosina <jikos@kernel.org>,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>,
        Bjorn Andersson <andersson@kernel.org>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Sam Ravnborg <sam@ravnborg.org>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>
Cc:     dri-devel@lists.freedesktop.org, linux-input@vger.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>, hsinyi@google.com,
        devicetree@vger.kernel.org,
        yangcong5@huaqin.corp-partner.google.com,
        linux-kernel@vger.kernel.org, Daniel Vetter <daniel@ffwll.ch>,
        linux-arm-msm@vger.kernel.org, cros-qcom-dts-watchers@chromium.org,
        Douglas Anderson <dianders@chromium.org>
Subject: [PATCH 8/9] HID: i2c-hid: Do panel follower work on the system_wq
Date:   Tue, 23 May 2023 12:28:02 -0700
Message-ID: <20230523122802.8.I962bb462ede779005341c49320740ed95810021d@changeid>
In-Reply-To: <20230523193017.4109557-1-dianders@chromium.org>
References: <20230523193017.4109557-1-dianders@chromium.org>
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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@chromium.org>
---

 drivers/hid/i2c-hid/i2c-hid-core.c | 42 +++++++++++++++++++++++++++---
 1 file changed, 38 insertions(+), 4 deletions(-)

diff --git a/drivers/hid/i2c-hid/i2c-hid-core.c b/drivers/hid/i2c-hid/i2c-hid-core.c
index f1bb89377e8d..800f0dc6f6cf 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 @@ int i2c_hid_core_initial_power_up(struct i2c_hid *ihid)
 	return ret;
 }
 
-int i2c_hid_core_panel_prepared(struct drm_panel_follower *follower)
+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 +1077,44 @@ 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);
+
+	/* Match with i2c_hid_core_panel_unpreparing() */
+	smp_wmb();
+}
+
+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;
 }
 
 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);
 }
 
@@ -1124,6 +1157,7 @@ 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
-- 
2.40.1.698.g37aff9b760-goog