From: Quanyang Wang quanyang.wang@windriver.com
When insmod zynqmp-dpsub.ko after rmmod it, system will hang with the error log as below:
root@xilinx-zynqmp:~# insmod zynqmp-dpsub.ko [ 88.391289] [drm] Initialized zynqmp-dpsub 1.0.0 20130509 for fd4a0000.display on minor 0 [ 88.529906] Console: switching to colour frame buffer device 128x48 [ 88.549402] zynqmp-dpsub fd4a0000.display: [drm] fb0: zynqmp-dpsubdrm frame buffer device [ 88.571624] zynqmp-dpsub fd4a0000.display: ZynqMP DisplayPort Subsystem driver probed root@xilinx-zynqmp:~# rmmod zynqmp_dpsub [ 94.023404] Console: switching to colour dummy device 80x25 root@xilinx-zynqmp:~# insmod zynqmp-dpsub.ko <hang here>
This is because that in zynqmp_dp_probe it tries to access some DP registers while the DP controller is still in the reset state. When running "rmmod zynqmp_dpsub", zynqmp_dp_reset(dp, true) in zynqmp_dp_phy_exit is called to force the DP controller into the reset state. Then insmod will call zynqmp_dp_probe to write to the DP registers, but at this moment the DP controller isn't brought out of the reset state since the function zynqmp_dp_reset(dp, false) is called later and this will result the system hang.
Releasing the reset to DP controller before any read/write operation to it will fix this issue.
Signed-off-by: Quanyang Wang quanyang.wang@windriver.com --- drivers/gpu/drm/xlnx/zynqmp_dp.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c index 99158ee67d02..bb45b3663d6b 100644 --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c @@ -402,10 +402,6 @@ static int zynqmp_dp_phy_init(struct zynqmp_dp *dp) } }
- ret = zynqmp_dp_reset(dp, false); - if (ret < 0) - return ret; - zynqmp_dp_clr(dp, ZYNQMP_DP_PHY_RESET, ZYNQMP_DP_PHY_RESET_ALL_RESET);
/* @@ -1682,6 +1678,10 @@ int zynqmp_dp_probe(struct zynqmp_dpsub *dpsub, struct drm_device *drm) return PTR_ERR(dp->reset); }
+ ret = zynqmp_dp_reset(dp, false); + if (ret < 0) + return ret; + ret = zynqmp_dp_phy_probe(dp); if (ret) return ret;