[PATCH v2] drm/probe_helper: sort out poll_running vs poll_enabled

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

There are two flags attemting to guard connector polling:
poll_enabled and poll_running. While poll_enabled semantics is clearly
defined and fully adhered (mark that drm_kms_helper_poll_init() was
called and not finalized by the _fini() call), the poll_running flag
doesn't have such clearliness.

This flag is used only in drm_helper_probe_single_connector_modes() to
guard calling of drm_kms_helper_poll_enable, it doesn't guard the
drm_kms_helper_poll_fini(), etc. Change it to only be set if the polling
is actually running. Tie HPD enablement to this flag.

This fixes the following warning reported after merging the HPD series:

Hot plug detection already enabled
WARNING: CPU: 2 PID: 9 at drivers/gpu/drm/drm_bridge.c:1257 drm_bridge_hpd_enable+0x94/0x9c [drm]
Modules linked in: videobuf2_memops snd_soc_simple_card snd_soc_simple_card_utils fsl_imx8_ddr_perf videobuf2_common snd_soc_imx_spdif adv7511 etnaviv imx8m_ddrc imx_dcss mc cec nwl_dsi gov
CPU: 2 PID: 9 Comm: kworker/u8:0 Not tainted 6.2.0-rc2-15208-g25b283acd578 #6
Hardware name: NXP i.MX8MQ EVK (DT)
Workqueue: events_unbound deferred_probe_work_func
pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : drm_bridge_hpd_enable+0x94/0x9c [drm]
lr : drm_bridge_hpd_enable+0x94/0x9c [drm]
sp : ffff800009ef3740
x29: ffff800009ef3740 x28: ffff000009331f00 x27: 0000000000001000
x26: 0000000000000020 x25: ffff800001148ed8 x24: ffff00000a8fe000
x23: 00000000fffffffd x22: ffff000005086348 x21: ffff800001133ee0
x20: ffff00000550d800 x19: ffff000005086288 x18: 0000000000000006
x17: 0000000000000000 x16: ffff8000096ef008 x15: 97ffff2891004260
x14: 2a1403e194000000 x13: 97ffff2891004260 x12: 2a1403e194000000
x11: 7100385f29400801 x10: 0000000000000aa0 x9 : ffff800008112744
x8 : ffff000000250b00 x7 : 0000000000000003 x6 : 0000000000000011
x5 : 0000000000000000 x4 : ffff0000bd986a48 x3 : 0000000000000001
x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff000000250000
Call trace:
 drm_bridge_hpd_enable+0x94/0x9c [drm]
 drm_bridge_connector_enable_hpd+0x2c/0x3c [drm_kms_helper]
 drm_kms_helper_poll_enable+0x94/0x10c [drm_kms_helper]
 drm_helper_probe_single_connector_modes+0x1a8/0x510 [drm_kms_helper]
 drm_client_modeset_probe+0x204/0x1190 [drm]
 __drm_fb_helper_initial_config_and_unlock+0x5c/0x4a4 [drm_kms_helper]
 drm_fb_helper_initial_config+0x54/0x6c [drm_kms_helper]
 drm_fbdev_client_hotplug+0xd0/0x140 [drm_kms_helper]
 drm_fbdev_generic_setup+0x90/0x154 [drm_kms_helper]
 dcss_kms_attach+0x1c8/0x254 [imx_dcss]
 dcss_drv_platform_probe+0x90/0xfc [imx_dcss]
 platform_probe+0x70/0xcc
 really_probe+0xc4/0x2e0
 __driver_probe_device+0x80/0xf0
 driver_probe_device+0xe0/0x164
 __device_attach_driver+0xc0/0x13c
 bus_for_each_drv+0x84/0xe0
 __device_attach+0xa4/0x1a0
 device_initial_probe+0x1c/0x30
 bus_probe_device+0xa4/0xb0
 deferred_probe_work_func+0x90/0xd0
 process_one_work+0x200/0x474
 worker_thread+0x74/0x43c
 kthread+0xfc/0x110
 ret_from_fork+0x10/0x20
---[ end trace 0000000000000000 ]---

Reported-by: Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>
Fixes: c8268795c9a9 ("drm/probe-helper: enable and disable HPD on connectors")
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---

Changes since v1:
- Fixed drm_kms_helper_enable_hpd() to call enable_hpd() instead of
  disable_hpd().

---
 drivers/gpu/drm/drm_probe_helper.c | 110 +++++++++++++++++------------
 1 file changed, 63 insertions(+), 47 deletions(-)

diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index 7973f2589ced..04754bb7b131 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -222,6 +222,45 @@ drm_connector_mode_valid(struct drm_connector *connector,
 	return ret;
 }
 
+static void drm_kms_helper_disable_hpd(struct drm_device *dev)
+{
+	struct drm_connector *connector;
+	struct drm_connector_list_iter conn_iter;
+
+	drm_connector_list_iter_begin(dev, &conn_iter);
+	drm_for_each_connector_iter(connector, &conn_iter) {
+		const struct drm_connector_helper_funcs *funcs =
+			connector->helper_private;
+
+		if (funcs && funcs->disable_hpd)
+			funcs->disable_hpd(connector);
+	}
+	drm_connector_list_iter_end(&conn_iter);
+}
+
+static bool drm_kms_helper_enable_hpd(struct drm_device *dev)
+{
+	bool poll = false;
+	struct drm_connector *connector;
+	struct drm_connector_list_iter conn_iter;
+
+	drm_connector_list_iter_begin(dev, &conn_iter);
+	drm_for_each_connector_iter(connector, &conn_iter) {
+		const struct drm_connector_helper_funcs *funcs =
+			connector->helper_private;
+
+		if (funcs && funcs->enable_hpd)
+			funcs->enable_hpd(connector);
+
+		if (connector->polled & (DRM_CONNECTOR_POLL_CONNECT |
+					 DRM_CONNECTOR_POLL_DISCONNECT))
+			poll = true;
+	}
+	drm_connector_list_iter_end(&conn_iter);
+
+	return poll;
+}
+
 #define DRM_OUTPUT_POLL_PERIOD (10*HZ)
 /**
  * drm_kms_helper_poll_enable - re-enable output polling.
@@ -241,26 +280,14 @@ drm_connector_mode_valid(struct drm_connector *connector,
 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;
 
-	if (!dev->mode_config.poll_enabled || !drm_kms_helper_poll)
+	if (!dev->mode_config.poll_enabled ||
+	    !drm_kms_helper_poll ||
+	    dev->mode_config.poll_running)
 		return;
 
-	drm_connector_list_iter_begin(dev, &conn_iter);
-	drm_for_each_connector_iter(connector, &conn_iter) {
-		const struct drm_connector_helper_funcs *funcs =
-			connector->helper_private;
-
-		if (funcs && funcs->enable_hpd)
-			funcs->enable_hpd(connector);
-
-		if (connector->polled & (DRM_CONNECTOR_POLL_CONNECT |
-					 DRM_CONNECTOR_POLL_DISCONNECT))
-			poll = true;
-	}
-	drm_connector_list_iter_end(&conn_iter);
+	poll = drm_kms_helper_enable_hpd(dev);
 
 	if (dev->mode_config.delayed_event) {
 		/*
@@ -279,6 +306,8 @@ void drm_kms_helper_poll_enable(struct drm_device *dev)
 
 	if (poll)
 		schedule_delayed_work(&dev->mode_config.output_poll_work, delay);
+
+	dev->mode_config.poll_running = true;
 }
 EXPORT_SYMBOL(drm_kms_helper_poll_enable);
 
@@ -567,10 +596,7 @@ 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(dev);
-
-	dev->mode_config.poll_running = drm_kms_helper_poll;
+	drm_kms_helper_poll_enable(dev);
 
 	if (connector->status == connector_status_disconnected) {
 		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n",
@@ -710,8 +736,12 @@ static void output_poll_execute(struct work_struct *work)
 	changed = dev->mode_config.delayed_event;
 	dev->mode_config.delayed_event = false;
 
-	if (!drm_kms_helper_poll)
+	if (!drm_kms_helper_poll &&
+	    dev->mode_config.poll_running) {
+		drm_kms_helper_disable_hpd(dev);
+		dev->mode_config.poll_running = false;
 		goto out;
+	}
 
 	if (!mutex_trylock(&dev->mode_config.mutex)) {
 		repoll = true;
@@ -808,30 +838,6 @@ bool drm_kms_helper_is_poll_worker(void)
 }
 EXPORT_SYMBOL(drm_kms_helper_is_poll_worker);
 
-static void drm_kms_helper_poll_disable_fini(struct drm_device *dev, bool fini)
-{
-	struct drm_connector *connector;
-	struct drm_connector_list_iter conn_iter;
-
-	if (!dev->mode_config.poll_enabled)
-		return;
-
-	if (fini)
-		dev->mode_config.poll_enabled = false;
-
-	drm_connector_list_iter_begin(dev, &conn_iter);
-	drm_for_each_connector_iter(connector, &conn_iter) {
-		const struct drm_connector_helper_funcs *funcs =
-			connector->helper_private;
-
-		if (funcs && funcs->disable_hpd)
-			funcs->disable_hpd(connector);
-	}
-	drm_connector_list_iter_end(&conn_iter);
-
-	cancel_delayed_work_sync(&dev->mode_config.output_poll_work);
-}
-
 /**
  * drm_kms_helper_poll_disable - disable output polling
  * @dev: drm_device
@@ -848,7 +854,12 @@ static void drm_kms_helper_poll_disable_fini(struct drm_device *dev, bool fini)
  */
 void drm_kms_helper_poll_disable(struct drm_device *dev)
 {
-	drm_kms_helper_poll_disable_fini(dev, false);
+	if (dev->mode_config.poll_running)
+		drm_kms_helper_disable_hpd(dev);
+
+	cancel_delayed_work_sync(&dev->mode_config.output_poll_work);
+
+	dev->mode_config.poll_running = false;
 }
 EXPORT_SYMBOL(drm_kms_helper_poll_disable);
 
@@ -886,7 +897,12 @@ EXPORT_SYMBOL(drm_kms_helper_poll_init);
  */
 void drm_kms_helper_poll_fini(struct drm_device *dev)
 {
-	drm_kms_helper_poll_disable_fini(dev, true);
+	if (!dev->mode_config.poll_enabled)
+		return;
+
+	drm_kms_helper_poll_disable(dev);
+
+	dev->mode_config.poll_enabled = false;
 }
 EXPORT_SYMBOL(drm_kms_helper_poll_fini);
 
-- 
2.39.0