Hi, On 04/05/2024 00:54, Sean Anderson wrote:
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
I wasn't able to reproduce. Where does the detect call come in your case? Looking at the code, afaics, it shouldn't happen.
Tomi
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; }
