[PATCH] nfc: trf7970a: power down on startup RX gain failure

[Myeonghun Pak <mhun512@gmail.com>]

trf7970a_startup() powers up the device before applying the optional RX
gain reduction. If the register read or write fails, it returns without
undoing that power-up. Probe's unwind only drops the separate regulator
references acquired by probe, leaving the additional VIN enable from
startup unbalanced. The system resume caller also has no power-down on
this error.

Call trf7970a_power_down() before returning the RX gain error to deassert
the enable GPIOs, release the startup VIN reference and restore the
powered-off state. Runtime PM has not been enabled yet, so the full
shutdown helper is not appropriate here. Preserve the original SPI error.

This issue was identified during our ongoing static-analysis research while
reviewing kernel code.

Fixes: 5d69351820ea ("NFC: trf7970a: Create device-tree parameter for RX gain reduction")
Cc: stable@vger.kernel.org
Assisted-by: OpenAI:GPT-5.6
Co-developed-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Myeonghun Pak <mhun512@gmail.com>
---
 drivers/nfc/trf7970a.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/nfc/trf7970a.c b/drivers/nfc/trf7970a.c
index 60883001f..ddfc58c29 100644
--- a/drivers/nfc/trf7970a.c
+++ b/drivers/nfc/trf7970a.c
@@ -1997,8 +1997,10 @@ static int trf7970a_startup(struct trf7970a *trf)
 		return ret;
 
 	ret = trf7970a_update_rx_gain_reduction(trf);
-	if (ret)
+	if (ret) {
+		trf7970a_power_down(trf);
 		return ret;
+	}
 
 	pm_runtime_set_active(trf->dev);
 	pm_runtime_enable(trf->dev);