[PATCH AUTOSEL 5.14 130/252] drm: xlnx: zynqmp: release reset to DP controller before accessing DP registers

Sasha Levin
2021-09-09T11:52:09Z

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 82430ca9b913..6f588dc09ba6 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)
@@ -1683,9 +1677,13 @@ 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,
@@ -1697,7 +1695,7 @@ 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);

@@ -1709,15 +1707,18 @@ 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;
}

@@ -1735,4 +1736,5 @@ 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