Hi Quanyang,
Thank you for the patch.
On Tue, Mar 23, 2021 at 10:55:01AM +0800, quanyang.wang@xxxxxxxxxxxxx wrote:
> From: Quanyang Wang <quanyang.wang@xxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxx>
Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> ---
>
> 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);
> }
--
Regards,
Laurent Pinchart
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