From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: quanyang.wang@windriver.com
Cc: Hyun Kwon <hyun.kwon@xilinx.com>, David Airlie <airlied@linux.ie>,
Michal Simek <michal.simek@xilinx.com>,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] drm: xlnx: zynqmp: release reset to DP controller before accessing DP registers
Date: Sat, 20 Mar 2021 22:08:59 +0200 [thread overview]
Message-ID: <YFZWW8IPhVff/VkS@pendragon.ideasonboard.com> (raw)
In-Reply-To: <20210320083739.724246-1-quanyang.wang@windriver.com>
Hi Quanyang,
Thank you for the patch.
On Sat, Mar 20, 2021 at 04:37:39PM +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 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;
> +
This change looks good to me.
> ret = zynqmp_dp_phy_probe(dp);
> if (ret)
> return ret;
But shouldn't we call zynqmp_dp_reset(dp, true) here ? Or rather, call
it in the error path at the end of the function, with a goto label.
For symmetry, should we also move the zynqmp_dp_reset() call from
zynqmp_dp_phy_exit() to zynqmp_dp_remove() ?
--
Regards,
Laurent Pinchart
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next prev parent reply other threads:[~2021-03-20 20:09 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-20 8:37 [PATCH] drm: xlnx: zynqmp: release reset to DP controller before accessing DP registers quanyang.wang
2021-03-20 20:08 ` Laurent Pinchart [this message]
2021-03-22 9:43 ` quanyang.wang
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