Hi Maxime,
On 29/10/2026 09:33, Maxime Ripard wrote:
Hi,
Here's a series that implement what i915 calls "fastboot", ie,
initializing the initial KMS state from the hardware state at boot, to
skip the first modeset if the firmware already set up the display.
This series creates the infrastructure in KMS to create that state by
relying on driver specific hooks. It also implements some infrastructure
to check during non-blocking commits that the readout helpers work
properly by reading out the state that was just committed and comparing
it to what was supposed to be committed.
This relies on another set of driver hooks to compare the entities
states, with helpers providing the default implementation.
It then implements the readout support in the TIDSS driver, and was
tested with the SK-AM62 board. This board in particular is pretty
interesting, since it relies on an DPI to HDMI bridge, and uses the
drm_bridge_connector infrastructure.
So the readout works with the current state of the art on embedded-ish
platforms.
Unlike the earlier RFCs, it now works fine: the state is picked up
properly, doesn't trigger a modeset if what was programmed is the one
the first modeset tries to pick as well, will switch properly if it
isn't, etc.
Sorry that I haven't had time to properly test and work on this. Here's
some quick feedback.
Do you have a branch you use to test this, with additional patches? If
so, could you always push that somewhere when posting the series (and
mention it in the cover letter).
Not directly related to this series, but the series doesn't compile as
modules, as drm_atomic_helper_colorop_create_state() is missing an export.
In an earlier version you had "drm/tidss: Switch to
drm_mode_config_create_initial_state()". Isn't that still needed?
Without it, the boot SRO is not done at all (which made me think you
have additional patches in a local branch).
I think you have AM62-SK board without the OLDI display. Even without
it, you can see what happens when OLDI is enabled by loading the
k3-am625-sk-microtips-mf101hie-panel.dtbo overlay. You won't see
anything displayed, of course, but otherwise it should load and work
fine, and HDMI should continue working.
I've done some testing, and there are quite a lot of combinations to try
out:
1) u-boot enables nothing, HDMI, OLDI or HDMI+OLDI, 2) OLDI dtbo loaded
or not (i.e. kernel see HDMI or HDMI+OLDI), 3) drm.atomic_readout set to
0 or 1, 4) a display pipeline's drivers (e.g. OLDI here) missing SRO
support, but other pipelines have SRO, 5) the first use from the
userspace is HDMI, OLDI or both, 6) with and without the
drm_mode_config_create_initial_state().
So... It's quite a lot of combinations there, and laborious to test. I
have some hack fixes in my local branch, and I'll try to find the time
to organize them a bit so that I can share them.
But here are a few observations:
1)
Setup: No display in u-boot. OLDI dtbo not loaded. Only the
drm_atomic_helper_colorop_create_state() fixup applied. Afaics behavior
here should be exactly as before the series, as SRO is not enabled for
tidss.
If I enable HDMI after boot, I get:
[ 38.203024] tidss 30200000.dss: [drm] *ERROR* crtc-0 configuration
mismatch in mode_blob blobs don't match
[ 38.203067] tidss 30200000.dss: [drm] [CRTC:42:crtc-0] Committed and
Readout CRTC state don't match
[ 104.468776] tidss 30200000.dss: [drm] *ERROR* crtc-0 configuration
mismatch in connector_mask expected 1, got 0
[ 104.468897] tidss 30200000.dss: [drm] *ERROR* crtc-0 configuration
mismatch in encoder_mask expected 1, got 0
[ 104.468976] tidss 30200000.dss: [drm] *ERROR* crtc-0 configuration
mismatch in mode_blob blobs don't match
[ 104.469047] tidss 30200000.dss: [drm] [CRTC:42:crtc-0] Committed and
Readout CRTC state don't match
If I do load OLDI dtbo or set atomic_readout=0, I don't see those, as
SRO support gets disabled. My understanding of this issue is that the
operation overall is fine, but the state comparison doesn't work quite
right.
2)
Setup: HDMI+OLDI in u-boot. OLDI dtbo loaded. Only the
drm_atomic_helper_colorop_create_state() fixup applied.
Enabling both displays after boot gives a sync lost flood and broken
display output.
I think the issue here is that tidss does not reset the HW anymore (even
if we don't call drm_mode_config_create_initial_state()), and the driver
doesn't fully rewrite all the relevant DSS registers (or doesn't do it
in a correct sequence, as it doesn't expect the VPs to be enabled at
this point).
3)
Setup: No display in u-boot. OLDI dtbo loaded.
drm_mode_config_create_initial_state() applied. So here we have HDMI
pipeline, where drivers have SRO support, and OLDI, where they don't.
Loading the modules gives:
[ 43.086356] tidss 30200000.dss: [drm] Device doesn't support hardware
state readout.
[ 43.086417] tidss 30200000.dss: Failed to set DSS PM to active
[ 43.086429] tidss 30200000.dss: [drm] Couldn't reset dispc
Otherwise the displays seem to work ok.
4)
As 3) but HDMI+OLDI enabled at u-boot.
Same outputs at module load time. Using the displays break badly,
probably because the driver doesn't re-program the registers fully.
5)
Setup: HDMI u-boot. OLDI dtbo not loaded.
drm_mode_config_create_initial_state() applied. I think this is the
setup you have been using.
No extra prints when loading modules. Running "kmstest -c hdmi" works
fine, but prints:
[ 62.464207] tidss 30200000.dss: [drm] *ERROR* crtc-0 configuration
mismatch in mode_blob blobs don't match
[ 62.464252] tidss 30200000.dss: [drm] [CRTC:42:crtc-0] Committed and
Readout CRTC state don't match
and when exiting kmstest:
[ 89.227700] tidss 30200000.dss: [drm] *ERROR* crtc-0 configuration
mismatch in connector_mask expected 1, got 0
[ 89.227820] tidss 30200000.dss: [drm] *ERROR* crtc-0 configuration
mismatch in encoder_mask expected 1, got 0
[ 89.227898] tidss 30200000.dss: [drm] *ERROR* crtc-0 configuration
mismatch in mode_blob blobs don't match
[ 89.227969] tidss 30200000.dss: [drm] [CRTC:42:crtc-0] Committed and
Readout CRTC state don't match
Running kmsblank gives:
[ 109.381641] tidss 30200000.dss: Timeout waiting for framedone on crtc 1
[ 109.387107] tidss 30200000.dss: [drm] *ERROR* crtc-0 configuration
mismatch in enable expected yes, got no
[ 109.387154] tidss 30200000.dss: [drm] *ERROR* crtc-0 configuration
mismatch in bus_format expected 0000100a, got 00000000
[ 109.387181] tidss 30200000.dss: [drm] *ERROR* crtc-0 configuration
mismatch in bus_flags expected 00000046, got 00000000
[ 109.387205] tidss 30200000.dss: [drm] [CRTC:42:crtc-0] Committed and
Readout CRTC state don't match
[ 109.387227] tidss 30200000.dss: [drm] *ERROR* HDMI-A-1 configuration
mismatch in crtc expected 00000000a0b1f61b, got 000000
[ 109.387255] tidss 30200000.dss: [drm] *ERROR* HDMI-A-1 configuration
mismatch in best_encoder expected 000000002b9c6290, g0
[ 109.387286] tidss 30200000.dss: [drm] [CONNECTOR:44:HDMI-A-1]
Committed and Readout connector state don't match
[ 109.387306] tidss 30200000.dss: [drm] *ERROR* bridge-30200000.dss
configuration mismatch in input_bus_cfg.format expected 0
[ 109.387332] tidss 30200000.dss: [drm] *ERROR* bridge-30200000.dss
configuration mismatch in input_bus_cfg.flags expected 00
[ 109.387356] tidss 30200000.dss: [drm] *ERROR* bridge-30200000.dss
configuration mismatch in output_bus_cfg.format expected0
[ 109.387380] tidss 30200000.dss: [drm] *ERROR* bridge-30200000.dss
configuration mismatch in output_bus_cfg.flags expected 0
[ 109.387403] tidss 30200000.dss: [drm] Committed and Readout private
object state don't match
[ 109.387420] tidss 30200000.dss: [drm] *ERROR* bridge-1-003b
configuration mismatch in input_bus_cfg.format expected 0000100
[ 109.387444] tidss 30200000.dss: [drm] *ERROR* bridge-1-003b
configuration mismatch in input_bus_cfg.flags expected 00000040
[ 109.387467] tidss 30200000.dss: [drm] *ERROR* bridge-1-003b
configuration mismatch in output_bus_cfg.format expected 000010
[ 109.387491] tidss 30200000.dss: [drm] Committed and Readout private
object state don't match
[ 109.387507] tidss 30200000.dss: [drm] *ERROR* bridge-connector-hdmi
configuration mismatch in input_bus_cfg.format expecte0
[ 109.387532] tidss 30200000.dss: [drm] *ERROR* bridge-connector-hdmi
configuration mismatch in output_bus_cfg.format expect0
[ 109.387555] tidss 30200000.dss: [drm] Committed and Readout private
object state don't match
If I run kmsblank as the first thing after loading modules:
[ 23.508008] tidss 30200000.dss: [drm] drm_WARN_ON_ONCE(!fb->obj[plane])
[ 23.508210] WARNING: drivers/gpu/drm/drm_gem_framebuffer_helper.c:62
at drm_gem_fb_get_obj+0xa4/0x120 [drm_kms_helper], CP5
Tomi
