Hi Thomas,
Thanks for the clarifications! Made a couple of remarks in-line.
On 4/6/23 14:29, Thomas Zimmermann wrote:
Hi
Am 06.04.23 um 11:17 schrieb Marius Vlad:
Hi Maira,
Thanks a lot for taking a look. Yeah, indeed, this creates a new
connector, a CRTC and planes for it. Terminology wise, multiple pipes.
The idea is to have multiple outputs, each with its own connector, as
to be able to simulate (a few) more outputs. At least that's what I'm
looking for.
I'll adjust the commits description to clarify that.
Regarding the planes, it seemed a bit easier to just create a new
tuple of planes for each output, as in to reuse vkms_output_init(). So
I guess that you're suggestion would be to make use the existing planes.
Seems a bit more work, not that keen on changing that, but I do have
some follow-up questions for my own curiosity in case I do this:
- Don't I need an entire pipe (a primary plane, crtc, encoder,
connector) to power up the end side of the sink (display)?
Yes, you need at least one full pipeline. I don't see how you'd get
something displayed otherwise.
- Can the primary one be sufficient for multiple outputs?
We have no concept of "primary pipelines." The individual components
have index numbers. There's a primary plane attached to each CRTC, but
even that concept comes more from HW limitations and historical designs,
than fundamental requirements.
Right, meant the primary plane, rather than pipeline.
For multiple outputs, you can attach multiple encoders/connectors to the
same CRTC. They will then all display the same screen at the same
display resolution
Yeah, this kind of sounds like cloning to me, and would like to display
different things at the same time, on different outputs, to me it sounds
I need primary plane and a CRTC for each connector. Right?
- Can the overlay planes be shared or I need to
discard the ones that are already in-use by other outputs?
Even if your hardware planes support it, you cannot share planes among
CRTCs with DRM. At least I'm not aware how to. Each plane struct has a
designated CRTC struct. For most flexibility I'd have to match HW planes
and DRM planes dynamically. For example if you have 2 CRTCs that can
share 10 HW planes, you can allocate 10 DRM planes for each CRTC. The
atomic_check functions have to implement the mapping from hardware to
software plane and fail if no more hardware planes are available.
If you want to display the same screen on multiple CRTCs, it's possible
to share the DRM framebuffers among similar the planes.
Aham, understood, thanks again!
Best regards
Thomas
I'll have a look at that writeback test as well see what's causing that
NULL pointer deref.
On 4/5/23 16:51, Maíra Canal wrote:
Hi Marius,
This patch adds support for creating multiple virtual connectors, in
case one would need it. Use module parameters to specify how many,
defaulting to just one, allocating from the start, a maximum of 4
possible outputs.
I got a bit confused by this description. The commit message says
that you
are creating multiple connectors, but it seems like you are creating
multiple
pipes. From what I could see, for each new connector created, you are
also
creating a new CRTC and new planes.
Moreover, if your real intention is to create multiple pipes, I
believe that
you don't really need to duplicate the planes as well.
I ran the VKMS CI [1] with your patches applied and, although most of
the
tests are now passing with multiple pipes, which is really nice, the
test
kms_writeback crashes with the following error:
[ 1997.244347] [IGT] kms_writeback: starting subtest
writeback-check-output
[ 1997.250673] BUG: kernel NULL pointer dereference, address:
000000000000016c
[ 1997.250691] #PF: supervisor read access in kernel mode
[ 1997.250693] #PF: error_code(0x0000) - not-present page
[ 1997.250694] PGD 800000001a877067 P4D 800000001a877067 PUD 1a872067
PMD 0
[ 1997.250697] Oops: 0000 [#1] PREEMPT SMP PTI
[ 1997.250699] CPU: 2 PID: 3223 Comm: kms_writeback Not tainted
6.3.0-rc4-g8c2c29ba129f-dirty #257
[ 1997.250701] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.16.2-1.fc37 04/01/2014
[ 1997.250703] RIP: 0010:drm_vblank_get+0xa/0xe0
[ 1997.250710] Code: a9 66 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 55 41 57 41 56 41 55
41 54 53 <8b> 87 6c 01 00 00 41 bc ea ff ff ff 85 c0 74 74 89 f5 48
89 fb 39
[ 1997.250712] RSP: 0018:ffffb84d407a3b08 EFLAGS: 00010202
[ 1997.250714] RAX: 0000000000000000 RBX: ffffa2eb02bf8b70 RCX:
0000000000000000
[ 1997.250718] RDX: ffffa2eb180d2420 RSI: 0000000000000000 RDI:
0000000000000000
[ 1997.250719] RBP: ffffa2eb02bf99e8 R08: 0000000000000036 R09:
ffffa2eb01d620c0
[ 1997.250720] R10: ffffe82b84027e40 R11: ffffffffc0042520 R12:
ffffa2eb01c01900
[ 1997.250721] R13: ffffa2eb02bf9b60 R14: 0000000000000001 R15:
ffffa2ea1ecd6b80
[ 1997.250722] FS: 00007f7d44e89a80(0000) GS:ffffa2eb3bd00000(0000)
knlGS:0000000000000000
[ 1997.250723] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1997.250725] CR2: 000000000000016c CR3: 000000001ec02000 CR4:
00000000000006e0
[ 1997.250728] Call Trace:
[ 1997.250735] <TASK>
[ 1997.250736] vkms_set_composer+0x18/0x60 [vkms]
[ 1997.250745] vkms_wb_atomic_commit+0x93/0x150 [vkms]
[ 1997.250749] drm_atomic_helper_commit_modeset_enables+0x1d9/0x250
[ 1997.250754] vkms_atomic_commit_tail+0x33/0xb0 [vkms]
[ 1997.250758] commit_tail+0x8d/0x170
[ 1997.250761] drm_atomic_helper_commit+0x26b/0x280
[ 1997.250763] drm_atomic_commit+0x9f/0xc0
[ 1997.250766] ? __pfx___drm_printfn_info+0x10/0x10
[ 1997.250769] drm_mode_atomic_ioctl+0x34c/0x480
[ 1997.250771] ? __pfx_drm_mode_atomic_ioctl+0x10/0x10
[ 1997.250773] drm_ioctl_kernel+0xd7/0x150
[ 1997.250780] drm_ioctl+0x31f/0x490
[ 1997.250781] ? __pfx_drm_mode_atomic_ioctl+0x10/0x10
[ 1997.250783] __se_sys_ioctl+0x6d/0xb0
[ 1997.250789] do_syscall_64+0x43/0x90
[ 1997.250795] entry_SYSCALL_64_after_hwframe+0x72/0xdc
[1]
https://gitlab.freedesktop.org/drm/igt-gpu-tools/-/tree/master/tests/vkms_ci
Best Regards,
- Maíra Canal
This is of particular importance when testing out the DRM backend in
compositors, but also to be able to independently handle multiple
outputs/connectors, like setting one to off/sleep on while the others
are on, and combinations that arise from that.
Signed-off-by: Marius Vlad <marius.vlad@xxxxxxxxxxxxx>
---
drivers/gpu/drm/vkms/vkms_crtc.c | 3 +--
drivers/gpu/drm/vkms/vkms_drv.c | 26 ++++++++++++++++++++++----
drivers/gpu/drm/vkms/vkms_drv.h | 8 +++++---
drivers/gpu/drm/vkms/vkms_output.c | 5 ++---
drivers/gpu/drm/vkms/vkms_writeback.c | 18 ++++++++----------
5 files changed, 38 insertions(+), 22 deletions(-)
