Re: [PATCH] drm/vc4: dsi: Only register our component once a DSI device is attached
From: Laurent Pinchart
Date: Sun Jun 20 2021 - 18:54:16 EST
Hi Dave,
On Sun, Jun 20, 2021 at 09:42:27PM +0300, Laurent Pinchart wrote:
> On Sun, Jun 20, 2021 at 03:29:03PM +0100, Dave Stevenson wrote:
> > On Sun, 20 Jun 2021 at 04:26, Laurent Pinchart wrote:
> > >
> > > Hi Maxime,
> > >
> > > I'm testing this, and I'm afraid it causes an issue with all the
> > > I2C-controlled bridges. I'm focussing on the newly merged ti-sn65dsi83
> > > driver at the moment, but other are affected the same way.
> > >
> > > With this patch, the DSI component is only added when the DSI device is
> > > attached to the host with mipi_dsi_attach(). In the ti-sn65dsi83 driver,
> > > this happens in the bridge attach callback, which is called when the
> > > bridge is attached by a call to drm_bridge_attach() in vc4_dsi_bind().
> > > This creates a circular dependency, and the DRM/KMS device is never
> > > created.
> > >
> > > How should this be solved ? Dave, I think you have shown an interest in
> > > the sn65dsi83 recently, any help would be appreciated. On a side note,
> > > I've tested the ti-sn65dsi83 driver on a v5.10 RPi kernel, without much
> > > success (on top of commit e1499baa0b0c I get a very weird frame rate -
> > > 147 fps of 99 fps instead of 60 fps - and nothing on the screen, and on
> > > top of the latest v5.10 RPi branch, I get lock-related warnings at every
> > > page flip), which is why I tried v5.12 and noticed this patch. Is it
> > > worth trying to bring up the display on the v5.10 RPi kernel in parallel
> > > to fixing the issue introduced in this patch, or is DSI known to be
> > > broken there ?
> >
> > I've been looking at SN65DSI83/4, but as I don't have any hardware
> > I've largely been suggesting things to try to those on the forums who
> > do [1].
> >
> > My branch at https://github.com/6by9/linux/tree/rpi-5.10.y-sn65dsi8x-marek
> > is the latest one I've worked on. It's rpi-5.10.y with Marek's driver
> > cherry-picked, and an overlay and simple-panel definition by others.
> > It also has a rework for vc4_dsi to use pm_runtime, instead of
> > breaking up the DSI bridge chain (which is flawed as it never calls
> > the bridge mode_set or mode_valid functions which sn65dsi83 relies
> > on).
> >
> > I ran it on Friday in the lab and encountered an issue with vc4_dsi
> > should vc4_dsi_encoder_mode_fixup wish for a divider of 7 (required
> > for this 800x1280 panel over 4 lanes) where it resulted in an invalid
> > mode configuration. That resulted in patch [2] which then gave me
> > sensible numbers.
> >
> > That branch with dtoverlay=vc4-kms-v3d and
> > dtoverlay=vc4-kms-dsi-ti-sn65dsi83 created all the expected devices,
> > and everything came up normally.
> > It was a busy day, but I think I even stuck a scope on the clock lanes
> > at that point and confirmed that they were at the link frequency
> > expected.
>
> Thanks, I'll test your branch and will report the results.
I had to apply the following diff to work around a crash:
diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
index 55b6c53207f5..647426aa793a 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
@@ -525,6 +525,9 @@ static bool sn65dsi83_mode_fixup(struct drm_bridge *bridge,
/* The DSI format is always RGB888_1X24 */
list_for_each_entry(connector, &ddev->mode_config.connector_list, head) {
+ if (!connector->display_info.bus_formats)
+ continue;
+
switch (connector->display_info.bus_formats[0]) {
case MEDIA_BUS_FMT_RGB666_1X7X3_SPWG:
ctx->lvds_format_24bpp = false;
connector->display_info.bus_formats is NULL for the HDMI connectors, as
I have nothing connected to them, as well as for the writeback
connector.
Then, when running kmstest --flip, I get one warning per frame:
[ 29.762089] [drm:vc4_dsi_runtime_resume] *ERROR* vc4_dsi_runtime_resume:
[ 29.763200] [drm:vc4_dsi_runtime_resume] *ERROR* vc4_dsi_runtime_resume: All good
[ 29.793861] ------------[ cut here ]------------
[ 29.798572] WARNING: CPU: 2 PID: 249 at drivers/gpu/drm/drm_modeset_lock.c:246 drm_modeset_lock+0xd0/0x100
[ 29.808365] Modules linked in: ipv6 bcm2835_codec(C) bcm2835_unicam bcm2835_v4l2(C) bcm2835_isp(C) bcm2835_mmal_vchiq(C) v4l2_mem2mem v4l2_dv_timings imx296 rtc_ds1307 videobuf2_vmallom
[ 29.855284] CPU: 2 PID: 249 Comm: kworker/u8:10 Tainted: G C 5.10.44-v8+ #23
[ 29.863756] Hardware name: Raspberry Pi Compute Module 4 Rev 1.0 (DT)
[ 29.870297] Workqueue: events_unbound commit_work
[ 29.875077] pstate: 80000005 (Nzcv daif -PAN -UAO -TCO BTYPE=--)
[ 29.881172] pc : drm_modeset_lock+0xd0/0x100
[ 29.885506] lr : drm_atomic_get_new_or_current_crtc_state+0x6c/0x110
[ 29.891950] sp : ffffffc011fcbcb0
[ 29.895308] x29: ffffffc011fcbcb0 x28: ffffff80403fe780
[ 29.900705] x27: ffffff80415a2000 x26: ffffffc0106f0000
[ 29.906100] x25: 0000000000000000 x24: ffffff80420d3c80
[ 29.911495] x23: ffffff8042174080 x22: 0000000000000038
[ 29.916890] x21: 0000000000000000 x20: ffffff80421740a8
[ 29.922284] x19: ffffffc011f8bc50 x18: 0000000000000000
[ 29.927678] x17: 0000000000000000 x16: 0000000000000000
[ 29.933072] x15: 0000000000000000 x14: 0000000000000000
[ 29.938466] x13: 0048000000000329 x12: 0326032303290320
[ 29.943860] x11: 03200000020301f4 x10: 00000000000019e0
[ 29.949255] x9 : ffffffc0106efd8c x8 : ffffff804390d5c0
[ 29.954649] x7 : 7fffffffffffffff x6 : 0000000000000001
[ 29.960043] x5 : 0000000000000001 x4 : 0000000000000001
[ 29.965436] x3 : ffffff80415a2000 x2 : ffffff804199b200
[ 29.970830] x1 : 00000000000000bc x0 : ffffffc011f8bc98
[ 29.976225] Call trace:
[ 29.978708] drm_modeset_lock+0xd0/0x100
[ 29.982687] drm_atomic_get_new_or_current_crtc_state+0x6c/0x110
[ 29.988781] vc4_atomic_complete_commit+0x4e4/0x860
[ 29.993729] commit_work+0x18/0x20
[ 29.997181] process_one_work+0x1c4/0x4a0
[ 30.001248] worker_thread+0x50/0x420
[ 30.004965] kthread+0x11c/0x150
[ 30.008239] ret_from_fork+0x10/0x20
[ 30.011865] ---[ end trace f44ae6b09cda951a ]---
Does it ring any bell ?
In case this is useful information, the problem didn't occur on top of
commit e1499baa0b0c.
> > Coming back to this patch though, it isn't in 5.10 so I'm not seeing
> > the issues. As to the exact ordering of attaches, I can't claim
> > sufficient knowledge on that front.
> > I can try a cherry-pick of this patch to see what goes on, but it
> > won't be for a day or two.
>
> Let's see if Maxime has an opinion :-)
>
> > [1] Largely https://www.raspberrypi.org/forums/viewtopic.php?f=44&t=305690,
> > but ignore about the first 5 pages of the thread as different driver
> > versions were floating about. Most stuff after that is based on
> > Marek's driver.
> > [2] https://github.com/6by9/linux/commit/c3c774136a1e946109048711d16974be8d520aaa
> >
> > > On Tue, Jul 07, 2020 at 12:19:12PM +0200, Maxime Ripard wrote:
> > > > If the DSI driver is the last to probe, component_add will try to run all
> > > > the bind callbacks straight away and return the error code.
> > > >
> > > > However, since we depend on a power domain, we're pretty much guaranteed to
> > > > be in that case on the BCM2711, and are just lucky on the previous SoCs
> > > > since the v3d also depends on that power domain and is further in the probe
> > > > order.
> > > >
> > > > In that case, the DSI host will not stick around in the system: the DSI
> > > > bind callback will be executed, will not find any DSI device attached and
> > > > will return EPROBE_DEFER, and we will then remove the DSI host and ask to
> > > > be probed later on.
> > > >
> > > > But since that host doesn't stick around, DSI devices like the RaspberryPi
> > > > touchscreen whose probe is not linked to the DSI host (unlike the usual DSI
> > > > devices that will be probed through the call to mipi_dsi_host_register)
> > > > cannot attach to the DSI host, and we thus end up in a situation where the
> > > > DSI host cannot probe because the panel hasn't probed yet, and the panel
> > > > cannot probe because the DSI host hasn't yet.
> > > >
> > > > In order to break this cycle, let's wait until there's a DSI device that
> > > > attaches to the DSI host to register the component and allow to progress
> > > > further.
> > > >
> > > > Suggested-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
> > > > Signed-off-by: Maxime Ripard <maxime@xxxxxxxxxx>
> > > > ---
> > > > drivers/gpu/drm/vc4/vc4_dsi.c | 25 ++++++++-----------------
> > > > 1 file changed, 8 insertions(+), 17 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c
> > > > index eaf276978ee7..19aab4e7e209 100644
> > > > --- a/drivers/gpu/drm/vc4/vc4_dsi.c
> > > > +++ b/drivers/gpu/drm/vc4/vc4_dsi.c
> > > > @@ -1246,10 +1246,12 @@ static ssize_t vc4_dsi_host_transfer(struct mipi_dsi_host *host,
> > > > return ret;
> > > > }
> > > >
> > > > +static const struct component_ops vc4_dsi_ops;
> > > > static int vc4_dsi_host_attach(struct mipi_dsi_host *host,
> > > > struct mipi_dsi_device *device)
> > > > {
> > > > struct vc4_dsi *dsi = host_to_dsi(host);
> > > > + int ret;
> > > >
> > > > dsi->lanes = device->lanes;
> > > > dsi->channel = device->channel;
> > > > @@ -1284,6 +1286,12 @@ static int vc4_dsi_host_attach(struct mipi_dsi_host *host,
> > > > return 0;
> > > > }
> > > >
> > > > + ret = component_add(&dsi->pdev->dev, &vc4_dsi_ops);
> > > > + if (ret) {
> > > > + mipi_dsi_host_unregister(&dsi->dsi_host);
> > > > + return ret;
> > > > + }
> > > > +
> > > > return 0;
> > > > }
> > > >
> > > > @@ -1662,7 +1670,6 @@ static int vc4_dsi_dev_probe(struct platform_device *pdev)
> > > > {
> > > > struct device *dev = &pdev->dev;
> > > > struct vc4_dsi *dsi;
> > > > - int ret;
> > > >
> > > > dsi = devm_kzalloc(dev, sizeof(*dsi), GFP_KERNEL);
> > > > if (!dsi)
> > > > @@ -1670,26 +1677,10 @@ static int vc4_dsi_dev_probe(struct platform_device *pdev)
> > > > dev_set_drvdata(dev, dsi);
> > > >
> > > > dsi->pdev = pdev;
> > > > -
> > > > - /* Note, the initialization sequence for DSI and panels is
> > > > - * tricky. The component bind above won't get past its
> > > > - * -EPROBE_DEFER until the panel/bridge probes. The
> > > > - * panel/bridge will return -EPROBE_DEFER until it has a
> > > > - * mipi_dsi_host to register its device to. So, we register
> > > > - * the host during pdev probe time, so vc4 as a whole can then
> > > > - * -EPROBE_DEFER its component bind process until the panel
> > > > - * successfully attaches.
> > > > - */
> > > > dsi->dsi_host.ops = &vc4_dsi_host_ops;
> > > > dsi->dsi_host.dev = dev;
> > > > mipi_dsi_host_register(&dsi->dsi_host);
> > > >
> > > > - ret = component_add(&pdev->dev, &vc4_dsi_ops);
> > > > - if (ret) {
> > > > - mipi_dsi_host_unregister(&dsi->dsi_host);
> > > > - return ret;
> > > > - }
> > > > -
> > > > return 0;
> > > > }
> > > >
--
Regards,
Laurent Pinchart