[PATCH v2] platform/raspberrypi: vchiq: register bus at subsys_initcall

Since 6.19-rc1, with CONFIG_BCM2835_VCHIQ=y and CONFIG_SND_BCM2835=y
(both builtin), the sound cards bcm2835_headphones and bcm2835_hdmi are
not detected anymore (vc4-hdmi is not affected).

dmesg shows:

  Driver 'bcm2835-audio' was unable to register with bus_type
  'vchiq-bus' because the bus was not initialized.

Since the VCHIQ interface was moved out of staging, its bus is no longer
guaranteed to be registered before its client drivers. bcm2835-audio,
still in drivers/staging, registers at device_initcall level and now
runs first.

Register the bus and the platform driver at subsys_initcall so the bus
exists before any client driver, independently of link order. The
platform driver probe already returns -EPROBE_DEFER while the firmware
is not ready, so probing earlier is safe. When built as modules, this is
equivalent to module_init() and nothing changes.

Tested on Raspberry Pi 1B rev2, 1B+, 2B, 3B and 4B with VCHIQ and
bcm2835-audio both builtin and both as modules.

Cc: stable@vger.kernel.org
Fixes: aa125180c673 ("platform/raspberrypi: Destage VCHIQ interface")
Reported-by: Martin Wetterwald <redacted>
Closes: https://lore.kernel.org/r/CAFERDQ0FpdVvA5VJxOyRAE_pgxnPVmFx1tkZio5R272j6Bs4tg@mail.gmail.com/ (local)
Reviewed-by: Jai Luthra <jai.luthra@ideasonboard.com>
Tested-by: Gaston Gonzalez <redacted> # Raspberry Pi Zero
Signed-off-by: Martin Wetterwald <redacted>
---
Hi Greg,
this is a regression introduced by aa125180c673 (via your tree) in
6.19-rc1 and present in 6.19.y through 7.3.y. If the staging pull for
7.4-rc1 has not been sent yet, could you take it there? Otherwise,
staging-linus would be great. Thanks!

v2:
- Reword commit message with more precise description
- Add Cc: stable@vger.kernel.org
- Remove redundant Link: pointing to same report as Closes:
- Collect Tested-by and Reviewed-by tags from v1
- Link to v1: https://lore.kernel.org/all/20261013131435.1454019-1-martin@wetterwald.eu/ (local)
---
 drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c b/drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c
index e78641703252..d35f5ac5c2e2 100644
--- a/drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c
+++ b/drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c

@@ -1462,7 +1462,7 @@ static int __init vchiq_driver_init(void)
 
 	return ret;
 }
-module_init(vchiq_driver_init);
+subsys_initcall(vchiq_driver_init);
 
 static void __exit vchiq_driver_exit(void)
 {

-- 
2.56.0