Re: [PATCH v1 05/35] drm/connector: Add TV standard property

["Noralf Trønnes" <noralf@tronnes.org>]

Den 18.08.2022 17.31, skrev Maxime Ripard:
> On Thu, Aug 18, 2022 at 05:01:38PM +0200, Noralf Trønnes wrote:
>>
>>
>> Den 18.08.2022 01.23, skrev Noralf Trønnes:
>>>
>>>
>>> Den 17.08.2022 15.11, skrev Noralf Trønnes:
>>>>
>>>>
>>>> Den 17.08.2022 13.46, skrev Maxime Ripard:
>>>>> On Tue, Aug 16, 2022 at 09:35:24PM +0200, Noralf Trønnes wrote:
>>>>>> Den 16.08.2022 11.49, skrev Maxime Ripard:
>>>>>>> On Tue, Aug 16, 2022 at 11:42:20AM +0200, Noralf Trønnes wrote:
>>>>>>>> Den 16.08.2022 10.26, skrev Maxime Ripard:
>>>>>>>>> Hi,
>>>>>>>>>
>>>>>>>>> On Mon, Aug 08, 2022 at 02:44:56PM +0200, Noralf Trønnes wrote:
>>>>>>>>>> Den 29.07.2022 18.34, skrev Maxime Ripard:
>>>>>>>>>>> The TV mode property has been around for a while now to select and get the
>>>>>>>>>>> current TV mode output on an analog TV connector.
>>>>>>>>>>>
>>>>>>>>>>> Despite that property name being generic, its content isn't and has been
>>>>>>>>>>> driver-specific which makes it hard to build any generic behaviour on top
>>>>>>>>>>> of it, both in kernel and user-space.
>>>>>>>>>>>
>>>>>>>>>>> Let's create a new bitmask tv norm property, that can contain any of the
>>>>>>>>>>> analog TV standards currently supported by kernel drivers. Each driver can
>>>>>>>>>>> then pass in a bitmask of the modes it supports.
>>>>>>>>>>>
>>>>>>>>>>> We'll then be able to phase out the older tv mode property.
>>>>>>>>>>>
>>>>>>>>>>> Signed-off-by: Maxime Ripard <maxime@cerno.tech>
>>>>>>>>>>>
>>>
>>>>>> How do you test the property? I've used modetest but I can only change
>>>>>> to a tv.mode that matches the current display mode. I can't switch from
>>>>>> ntsc to pal for instance.
>>>>>
>>>>> Yep, if you want to change from PAL to NTSC, it will require a new mode.
>>>>>
>>>>
>>>> So userspace has to check tv.mode first and then create a display mode
>>>> the driver will accept if switching to a different display mode is
>>>> necessary? In other words, userspace can't discover from the kernel
>>>> which display modes a certain tv.mode/norm provides before it is
>>>> selected? If so, maybe libdrm should have some function(s) to deal with
>>>> switching between modes that require a different display mode since
>>>> knowledge about which display modes a tv.mode supports is needed before
>>>> hand.
>>>>
>>>
>>> I haven't used vc4 on Pi4 in mainline before and have finally gotten it
>>> to work.
>>>
>>> I see that the connector reports 2 modes that together fit all tv.norms
>>> so userspace doesn't have to contruct a display mode, but it does need
>>> to know which display mode belongs to a certain tv.norm.
>>>
>>> When I try to use modetest I'm unable to set a mode:
>>>
>>> pi@pi4t:~ $ modetest -M vc4 -s 45:720x480i
>>> setting mode 720x480i-29.97Hz on connectors 45, crtc 68
>>> failed to set mode: Function not implemented
>>>
>>> The errno is misleading, modetest does a drmModeDirtyFB before checking
>>> the error returned by drmModeSetCrtc.
>>>
>>> Setting the property succeeds, but the modeset still fails:
>>>
>>> pi@pi4t:~ $ modetest -M vc4 -s 45:720x480i -w 45:"tv norm":2
>>> setting mode 720x480i-29.97Hz on connectors 45, crtc 68
>>> failed to set mode: Function not implemented
>>>
>>> pi@pi4t:~ $ modetest -M vc4 -c
>>>         37 tv norm:
>>>                 flags: bitmask
>>>                 values: NTSC-443=0x1 NTSC-J=0x2 NTSC-M=0x4 PAL-B=0x10
>>> PAL-M=0x200 PAL-N=0x400 SECAM-B=0x2000
>>>                 value: 2
>>>
>>> Here's the log, can you see if there's anything obvious in there:
>>> https://gist.github.com/notro/a079498bf6b64327105752b2bafa8858
>>>
>>
>> I'm one step closer as I now have fbcon working, I had forgotten to add
>> enable_tvout=1 and I had disable_fw_kms_setup=1 which disables the
>> video= mode on the kernel commandline.
>>
>> modetest still fails though, after alot of printk sprinkling, I've
>> tracked it down to the drm_mode_equal test in
>> drm_atomic_helper_connector_tv_check(). The aspect ratios differ:
>>
>> [   61.336295] drm_atomic_helper_connector_tv_check:
>> mode->picture_aspect_ratio=1
>> [   61.336301] drm_atomic_helper_connector_tv_check:
>> &crtc_state->mode->picture_aspect_ratio=0
> 
> I haven't seen this when testing, but I'll have a look, thanks!

I have found the cause, the kernel strips off the aspect ratio in
drm_mode_getconnector() if drm_file->aspect_ratio_allowed is false. So I
think the drm_mode_equal() test needs to be relaxed for
legacy/non-atomic userspace to work.

If I use modetest with atomic commit (-a) it works as is, having the
drm_mode_equal() test:

$ modetest -M vc4 -a -P 61@68:720x480 -s 45:720x480i

I have a problem because the board hangs, either right away or after I
press <enter> to quit modetest.

I often get this, sometimes after 10s of seconds:

[  136.822963] Unhandled fault: asynchronous external abort (0x1211) at
0x00000000
...
[  137.248496]  bcm2711_get_temp [bcm2711_thermal] from
thermal_zone_get_temp+0x54/0x74

Unloading bcm2711_thermal didn't help, in that case I got nothing, so
the problem lies elsewhere.
I have even tried with a fresh SD image and a fresh kernel, but it
didn't help.

I can switch from NTSC to PAL like this (but it still crashes):

$ modetest -M vc4 -a -w 45:"tv norm":16 -P 61@68:720x576 -s 45:720x576i

I had to patch modetest for that to work:

diff --git a/tests/modetest/modetest.c b/tests/modetest/modetest.c
index 8ff6c80d..accd2166 100644
--- a/tests/modetest/modetest.c
+++ b/tests/modetest/modetest.c
@@ -2188,12 +2187,13 @@ int main(int argc, char **argv)
 	dump_resource(&dev, planes);
 	dump_resource(&dev, framebuffers);

+	if (dev.use_atomic)
+		dev.req = drmModeAtomicAlloc();
+
 	for (i = 0; i < prop_count; ++i)
 		set_property(&dev, &prop_args[i]);

 	if (dev.use_atomic) {
-		dev.req = drmModeAtomicAlloc();
-
 		if (set_preferred || (count && plane_count)) {
 			uint64_t cap = 0;


I use a composite to USB adapter to see the output:
https://www.adafruit.com/product/4715

Noralf.

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