From: Sean Anderson <sean.anderson@linux.dev>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <mripard@kernel.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
Michal Simek <michal.simek@amd.com>,
dri-devel@lists.freedesktop.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: [BUG] drm: zynqmp_dp: Lockup in zynqmp_dp_bridge_detect when device is unbound
Date: Fri, 3 May 2024 17:54:32 -0400 [thread overview]
Message-ID: <4d8f4c9b-2efb-4774-9a37-2f257f79b2c9@linux.dev> (raw)
Hi,
I have discovered a bug in the displayport driver on drm-misc-next. To
trigger it, run
echo fd4a0000.display > /sys/bus/platform/drivers/zynqmp-dpsub/unbind
The system will become unresponsive and (after a bit) splat with a hard
LOCKUP. One core will be unresponsive at the first zynqmp_dp_read in
zynqmp_dp_bridge_detect.
I believe the issue is due the registers being unmapped and the block
put into reset in zynqmp_dp_remove instead of zynqmp_dpsub_release. This
could be resolved by deferring things until zynqmp_dpsub_release
(requiring us to skip devm_*), or by adding a flag to struct zynqmp_dp
and checking it before each callback. A subsystem-level implementation
might be better for the latter.
For a better traceback, try applying the below patch and running the
following commands before triggering the lockup:
echo 4 > /sys/module/drm/parameters/debug
echo 8 > /proc/sys/kernel/printk
diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
index 9df068a413f3..17b477b14ab5 100644
--- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
+++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
@@ -296,6 +296,7 @@ struct zynqmp_dp_config {
* @train_set: set of training data
*/
struct zynqmp_dp {
+ unsigned long long magic;
struct device *dev;
struct zynqmp_dpsub *dpsub;
void __iomem *iomem;
@@ -1533,6 +1534,8 @@ static enum drm_connector_status zynqmp_dp_bridge_detect(struct drm_bridge *brid
u32 state, i;
int ret;
+ WARN_ON(dp->magic != 0x0123456789abcdefULL);
+
/*
* This is from heuristic. It takes some delay (ex, 100 ~ 500 msec) to
* get the HPD signal with some monitors.
@@ -1723,6 +1726,7 @@ int zynqmp_dp_probe(struct zynqmp_dpsub *dpsub)
if (!dp)
return -ENOMEM;
+ dp->magic = 0x0123456789abcdefULL;
dp->dev = &pdev->dev;
dp->dpsub = dpsub;
dp->status = connector_status_disconnected;
@@ -1839,4 +1843,5 @@ void zynqmp_dp_remove(struct zynqmp_dpsub *dpsub)
zynqmp_dp_phy_exit(dp);
zynqmp_dp_reset(dp, true);
+ dp->magic = 0xdeadbeefdeadbeefULL;
}
next reply other threads:[~2024-05-03 21:54 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-03 21:54 Sean Anderson [this message]
2024-05-04 12:21 ` [BUG] drm: zynqmp_dp: Lockup in zynqmp_dp_bridge_detect when device is unbound Laurent Pinchart
2024-05-06 7:29 ` Maxime Ripard
2024-05-06 7:35 ` Laurent Pinchart
2024-05-06 14:57 ` Sean Anderson
2024-05-06 16:50 ` Laurent Pinchart
2024-05-07 7:58 ` Maxime Ripard
2024-05-06 11:16 ` Tomi Valkeinen
2024-05-06 14:46 ` Sean Anderson
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