Hi Quanyang,

Thank you for the patch.

On Tue, Mar 23, 2021 at 10:55:01AM +0800, quanyang.wang@windriver.com wrote:

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 program the DP registers, but at this moment the DP controller hasn't been brought out of the reset state yet 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. And for symmetry, move zynqmp_dp_reset() call from zynqmp_dp_phy_exit() to zynqmp_dp_remove().

Signed-off-by: Quanyang Wang quanyang.wang@windriver.com

Reviewed-by: Laurent Pinchart laurent.pinchart@ideasonboard.com

---

V2: According to Laurent's comments:

• add zynqmp_dp_reset(dp, true) in error path in zynqmp_dp_probe
• move the zynqmp_dp_reset() call from zynqmp_dp_phy_exit() to zynqmp_dp_remove()

---

drivers/gpu/drm/xlnx/zynqmp_dp.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c index 99158ee67d02..337adf0769ad 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);

  /*

@@ -441,8 +437,6 @@ static void zynqmp_dp_phy_exit(struct zynqmp_dp *dp) ret); }

• zynqmp_dp_reset(dp, true);
• for (i = 0; i < dp->num_lanes; i++) { ret = phy_exit(dp->phy[i]); if (ret)

@@ -1682,9 +1676,13 @@ 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;
  

• goto err_reset;
  
  

  /* Initialize the hardware. */ zynqmp_dp_write(dp, ZYNQMP_DP_TX_PHY_POWER_DOWN,

@@ -1696,7 +1694,7 @@ int zynqmp_dp_probe(struct zynqmp_dpsub *dpsub, struct drm_device *drm)

ret = zynqmp_dp_phy_init(dp); if (ret)

• return ret;
  

• goto err_reset;
  
  

  zynqmp_dp_write(dp, ZYNQMP_DP_TRANSMITTER_ENABLE, 1);

@@ -1708,15 +1706,18 @@ int zynqmp_dp_probe(struct zynqmp_dpsub *dpsub, struct drm_device *drm) zynqmp_dp_irq_handler, IRQF_ONESHOT, dev_name(dp->dev), dp); if (ret < 0)

• goto error;
  

• goto err_phy_exit;
  
  

  dev_dbg(dp->dev, "ZynqMP DisplayPort Tx probed with %u lanes\n", dp->num_lanes);

  return 0;

-error: +err_phy_exit: zynqmp_dp_phy_exit(dp); +err_reset:

• zynqmp_dp_reset(dp, true);
• return ret;

}

@@ -1734,4 +1735,5 @@ void zynqmp_dp_remove(struct zynqmp_dpsub *dpsub) zynqmp_dp_write(dp, ZYNQMP_DP_INT_DS, 0xffffffff);

zynqmp_dp_phy_exit(dp);

• zynqmp_dp_reset(dp, true);

}