[PATCH net v2] net: airoha: npu: load the firmware without the sysfs fallback

[PATCH net v2] 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.

Use request_firmware_direct() instead. It 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 intended.

Two consequences are worth stating plainly.

The helper is not merely bypassed for the boot-before-rootfs case.
fw_run_sysfs_fallback() returns early on FW_OPT_NOFALLBACK_SYSFS, so this
driver's firmware requests can no longer be served by a usermode helper
at all, including on a system where that is the only delivery route;
having no second firmware source, the driver would defer forever there.
That is a deliberate trade-off: the -ENOENT to -EPROBE_DEFER mapping was
written to wait for a filesystem, and the sysfs helper interface has had
no in-tree consumer since udev dropped firmware loading.

request_firmware_direct() also sets FW_OPT_NO_WARN, which drops the only
message naming the file that failed to load. Report it from the driver
instead, so the name lands in the deferred probe reason and shows up in
the "deferred probe pending" line emitted at
driver_deferred_probe_timeout. The generic report in airoha_npu_probe()
goes away with it, since it would otherwise overwrite that reason with a
message naming nothing; of the paths it covered, devm_ioremap_resource()
reports itself and the malformed firmware-name property now does too.

Measured on a Nokia XG-040G-MD with FW_LOADER_USER_HELPER=y and
FW_LOADER_USER_HELPER_FALLBACK=y forced on, two images from the same
tree differing only by this patch:

  without:  fallback at 2.477s -> -ETIMEDOUT at 64.555s -> probe failed
            with -110, preinit at 69.6s, NPU unbound
  with:     no fallback, NPU fw version 1456.62 at 3.665s, preinit at
            7.6s

Fixes: 23290c7bc190 ("net: airoha: Introduce Airoha NPU support")
Cc: stable@vger.kernel.org
Signed-off-by: Vitaliy Sochnev <sochnev.v.74@gmail.com>
---
v2:
 - Keep the file name in the diagnostics. request_firmware_direct() also
   sets FW_OPT_NO_WARN, which dropped the only message naming the file;
   report it from airoha_npu_load_firmware() through dev_err_probe() so
   the name lands in the deferred probe reason. Drop the generic report
   in airoha_npu_probe(), which would overwrite that reason, and give
   the malformed firmware-name path a message of its own.
 - Say in the changelog that the usermode helper path is disabled for
   this driver's requests rather than merely bypassed, and why that
   trade-off is acceptable.
 - Both points raised in review of v1:
   https://lore.kernel.org/netdev/20260807024125.434055-1-sochnev.v.74@gmail.com/

 drivers/net/ethernet/airoha/airoha_npu.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/airoha/airoha_npu.c b/drivers/net/ethernet/airoha/airoha_npu.c
index b679bed95..de75376db 100644
--- a/drivers/net/ethernet/airoha/airoha_npu.c
+++ b/drivers/net/ethernet/airoha/airoha_npu.c
@@ -202,9 +202,10 @@ 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;
+		return dev_err_probe(dev, ret == -ENOENT ? -EPROBE_DEFER : ret,
+				     "failed to load %s\n", fw_name);
 
 	if (fw->size > fw_max_size) {
 		dev_err(dev, "%s: fw size too overlimit (%zu)\n",
@@ -230,7 +231,8 @@ airoha_npu_load_firmware_from_dts(struct device *dev, void __iomem *addr,
 	ret = of_property_read_string_array(dev->of_node, "firmware-name",
 					    fw_names, ARRAY_SIZE(fw_names));
 	if (ret != ARRAY_SIZE(fw_names))
-		return -EINVAL;
+		return dev_err_probe(dev, -EINVAL,
+				     "invalid firmware-name property\n");
 
 	ret = airoha_npu_load_firmware(dev, addr, fw_names[0],
 				       NPU_EN7581_FIRMWARE_RV32_MAX_SIZE);
@@ -772,7 +774,7 @@ static int airoha_npu_probe(struct platform_device *pdev)
 
 	err = airoha_npu_run_firmware(dev, base, &res);
 	if (err)
-		return dev_err_probe(dev, err, "failed to run npu firmware\n");
+		return err;
 
 	regmap_write(npu->regmap, REG_CR_NPU_MIB(10),
 		     res.start + NPU_EN7581_FIRMWARE_RV32_MAX_SIZE);
-- 
2.55.0