On Thu, Sep 30, 2021 at 11:19:59AM +0200, Daniel Vetter wrote:
On Tue, Sep 28, 2021 at 10:34:46AM +0200, Maxime Ripard wrote:
Hi Daniel,
On Sat, Sep 25, 2021 at 12:50:17AM +0200, Daniel Vetter wrote:
On Fri, Sep 24, 2021 at 3:30 PM Maxime Ripard maxime@cerno.tech wrote:
On Wed, Sep 22, 2021 at 01:25:21PM -0700, Linus Torvalds wrote:
On Wed, Sep 22, 2021 at 1:19 PM Sudip Mukherjee sudipm.mukherjee@gmail.com wrote:
I added some debugs to print the addresses, and I am getting: [ 38.813809] sudip crtc 0000000000000000
This is from struct drm_crtc *crtc = connector->state->crtc;
Yeah, that was my personal suspicion, because while the line number implied "crtc->state" being NULL, the drm data structure documentation and other drivers both imply that "crtc" was the more likely one.
I suspect a simple
if (!crtc) return;in vc4_hdmi_set_n_cts() is at least part of the fix for this all, but I didn't check if there is possibly something else that needs to be done too.
Thanks for the decode_stacktrace.sh and the follow-up
Yeah, it looks like we have several things wrong here:
we only check that connector->state is set, and not connector->state->crtc indeed.
We also check only in startup(), so at open() and not later on when the sound streaming actually start. This has been there for a while, so I guess it's never really been causing a practical issue before.
You also have no locking
Indeed. Do we just need locking to prevent a concurrent audio setup and modeset, or do you have another corner case in mind?
Also, generally, what locks should we make sure we have locked when accessing the connector and CRTC state? drm_mode_config.connection_mutex and drm_mode_config.mutex, respectively?
plus looking at ->state objects outside of atomic commit machinery makes no sense because you're not actually in sync with the hw state. Relevant bits need to be copied over at commit time, protected by some spinlock (and that spinlock also needs to be held over whatever other stuff you're setting to make sure we don't get a funny out-of-sync state anywhere).
If we already have a lock protecting against having both an ASoC and KMS function running, it's not clear to me what the spinlock would prevent here?
Replicating the irc chat here. With
commit 6c5ed5ae353cdf156f9ac4db17e15db56b4de880 Author: Maarten Lankhorst maarten.lankhorst@linux.intel.com Date: Thu Apr 6 20:55:20 2017 +0200
drm/atomic: Acquire connection_mutex lock in drm_helper_probe_single_connector_modes, v4.this is already taken care of for drivers and should be all good from a locking pov.
So, if I understand this properly, this superseeds your comment on the spinlock for the hw state, but not the comment that we need some locking to synchronize between the audio and KMS path (and CEC?). Right?
Maxime