[PATCH net] net: airoha: npu: load the firmware without the sysfs fallback

[Vitaliy Sochnev]

airoha_npu_load_firmware() maps a missing firmware file to -EPROBE_DEFER
so that the NPU can be brought up once the rootfs carrying /lib/firmware
has been mounted. That mapping holds only as long as request_firmware()
reports -ENOENT.

It does not when the sysfs fallback is in play. With
CONFIG_FW_LOADER_USER_HELPER_FALLBACK set, or with the fallback armed at
runtime through /proc/sys/kernel/firmware_config/force_sysfs_fallback,
request_firmware() hands the request to a userspace helper, waits out the
full loading_timeout and returns -ETIMEDOUT. The -ENOENT test no longer
matches, dev_err_probe() turns the result into a hard failure, and the
NPU is left unbound after stalling the boot for 60 seconds:

  airoha-npu 1e900000.npu: Direct firmware load for airoha/en7581_npu_rv32.bin failed with error -2
  airoha-npu 1e900000.npu: Falling back to sysfs fallback for: airoha/en7581_npu_rv32.bin
  airoha-npu 1e900000.npu: error -ETIMEDOUT: failed to run npu firmware
  airoha-npu 1e900000.npu: probe with driver airoha-npu failed with error -110

Clearing FW_LOADER_USER_HELPER in the configuration is not a dependable
guard against this, because unrelated drivers select it. On the affected
build the symbol was turned back on by LEDS_LP55XX_COMMON, even though
the platform had explicitly disabled it.

request_firmware_direct() sets FW_OPT_NOFALLBACK_SYSFS, so a missing file
is reported as -ENOENT whatever the firmware loader is configured to do,
and the deferred probe path works as it was meant to.

Measured on a Nokia XG-040G-MD with FW_LOADER_USER_HELPER=y and
FW_LOADER_USER_HELPER_FALLBACK=y, on two images from the same tree
differing only by this patch: without it the probe fails with
-ETIMEDOUT after 64.5s and the NPU stays unbound, with it the NPU
reports its firmware version at 3.7s. The fallback is compiled in and
forced in both cases; the patch does not disable it, it only keeps the
driver from falling into it.

Fixes: 23290c7bc190 ("net: airoha: Introduce Airoha NPU support")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Vitaliy Sochnev <sochnev.v.74@xxxxxxxxx>
---
 drivers/net/ethernet/airoha/airoha_npu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/airoha/airoha_npu.c b/drivers/net/ethernet/airoha/airoha_npu.c
index b679bed95..ca33e615a 100644
--- a/drivers/net/ethernet/airoha/airoha_npu.c
+++ b/drivers/net/ethernet/airoha/airoha_npu.c
@@ -202,7 +202,7 @@ static int airoha_npu_load_firmware(struct device *dev, void __iomem *addr,
 	const struct firmware *fw;
 	int ret;
 
-	ret = request_firmware(&fw, fw_name, dev);
+	ret = request_firmware_direct(&fw, fw_name, dev);
 	if (ret)
 		return ret == -ENOENT ? -EPROBE_DEFER : ret;
 
-- 
2.55.0