From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Sean Anderson <sean.anderson@linux.dev>
Cc: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <mripard@kernel.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
Michal Simek <michal.simek@amd.com>,
dri-devel@lists.freedesktop.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [BUG] drm: zynqmp_dp: Lockup in zynqmp_dp_bridge_detect when device is unbound
Date: Sat, 4 May 2024 15:21:18 +0300 [thread overview]
Message-ID: <20240504122118.GB24548@pendragon.ideasonboard.com> (raw)
In-Reply-To: <4d8f4c9b-2efb-4774-9a37-2f257f79b2c9@linux.dev>
Hi Sean,
On Fri, May 03, 2024 at 05:54:32PM -0400, Sean Anderson wrote:
> Hi,
>
> I have discovered a bug in the displayport driver on drm-misc-next. To
> trigger it, run
>
> echo fd4a0000.display > /sys/bus/platform/drivers/zynqmp-dpsub/unbind
>
> The system will become unresponsive and (after a bit) splat with a hard
> LOCKUP. One core will be unresponsive at the first zynqmp_dp_read in
> zynqmp_dp_bridge_detect.
>
> I believe the issue is due the registers being unmapped and the block
> put into reset in zynqmp_dp_remove instead of zynqmp_dpsub_release.
That is on purpose. Drivers are not allowed to access the device at all
after .remove() returns.
> This
> could be resolved by deferring things until zynqmp_dpsub_release
> (requiring us to skip devm_*), or by adding a flag to struct zynqmp_dp
> and checking it before each callback. A subsystem-level implementation
> might be better for the latter.
>
> For a better traceback, try applying the below patch and running the
> following commands before triggering the lockup:
>
> echo 4 > /sys/module/drm/parameters/debug
> echo 8 > /proc/sys/kernel/printk
>
> diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> index 9df068a413f3..17b477b14ab5 100644
> --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
> +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> @@ -296,6 +296,7 @@ struct zynqmp_dp_config {
> * @train_set: set of training data
> */
> struct zynqmp_dp {
> + unsigned long long magic;
> struct device *dev;
> struct zynqmp_dpsub *dpsub;
> void __iomem *iomem;
> @@ -1533,6 +1534,8 @@ static enum drm_connector_status zynqmp_dp_bridge_detect(struct drm_bridge *brid
> u32 state, i;
> int ret;
>
> + WARN_ON(dp->magic != 0x0123456789abcdefULL);
> +
> /*
> * This is from heuristic. It takes some delay (ex, 100 ~ 500 msec) to
> * get the HPD signal with some monitors.
> @@ -1723,6 +1726,7 @@ int zynqmp_dp_probe(struct zynqmp_dpsub *dpsub)
> if (!dp)
> return -ENOMEM;
>
> + dp->magic = 0x0123456789abcdefULL;
> dp->dev = &pdev->dev;
> dp->dpsub = dpsub;
> dp->status = connector_status_disconnected;
> @@ -1839,4 +1843,5 @@ void zynqmp_dp_remove(struct zynqmp_dpsub *dpsub)
>
> zynqmp_dp_phy_exit(dp);
> zynqmp_dp_reset(dp, true);
> + dp->magic = 0xdeadbeefdeadbeefULL;
> }
--
Regards,
Laurent Pinchart
next prev parent reply other threads:[~2024-05-04 12:21 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-03 21:54 [BUG] drm: zynqmp_dp: Lockup in zynqmp_dp_bridge_detect when device is unbound Sean Anderson
2024-05-04 12:21 ` Laurent Pinchart [this message]
2024-05-06 7:29 ` Maxime Ripard
2024-05-06 7:35 ` Laurent Pinchart
2024-05-06 14:57 ` Sean Anderson
2024-05-06 16:50 ` Laurent Pinchart
2024-05-07 7:58 ` Maxime Ripard
2024-05-06 11:16 ` Tomi Valkeinen
2024-05-06 14:46 ` Sean Anderson
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20240504122118.GB24548@pendragon.ideasonboard.com \
--to=laurent.pinchart@ideasonboard.com \
--cc=airlied@gmail.com \
--cc=daniel@ffwll.ch \
--cc=dri-devel@lists.freedesktop.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=maarten.lankhorst@linux.intel.com \
--cc=michal.simek@amd.com \
--cc=mripard@kernel.org \
--cc=sean.anderson@linux.dev \
--cc=tomi.valkeinen@ideasonboard.com \
--cc=tzimmermann@suse.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).