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    Subject[PATCH AUTOSEL 5.10 095/176] drm: xlnx: zynqmp: release reset to DP controller before accessing DP registers
    Date
    From: Quanyang Wang <quanyang.wang@windriver.com>

    [ Upstream commit a338619bd76011035d462f0f9e8b2f24d7fe5a1e ]

    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>
    Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 59d1fb017da0..13811332b349 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);
    }
    --
    2.30.2
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