From: Pei Xiao <xiaopei01@kylinos.cn>
Date: Thu, 19 Mar 2026 03:06:41 +0000 (+0800)
Subject: spi: hisi-kunpeng: prevent infinite while() loop in hisi_spi_flush_fifo
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=9f61daf2c2debe9f5cf4e1a4471e56a89a6fe45a;p=thirdparty%2Fkernel%2Flinux.git

spi: hisi-kunpeng: prevent infinite while() loop in hisi_spi_flush_fifo

The hisi_spi_flush_fifo()'s inner while loop that lacks any timeout
mechanism. Maybe the hardware never becomes empty, the loop will spin
forever, causing the CPU to hang.

Fix this by adding a inner_limit based on loops_per_jiffy. The inner loop
now exits after approximately one jiffy if the FIFO remains non-empty, logs
a ratelimited warning, and breaks out of the outer loop. Additionally, add
a cpu_relax() inside the busy loop to improve power efficiency.

Fixes: c770d8631e18 ("spi: Add HiSilicon SPI Controller Driver for Kunpeng SoCs")
Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
Link: https://patch.msgid.link/d834ce28172886bfaeb9c8ca00cfd9bf1c65d5a1.1773889292.git.xiaopei01@kylinos.cn
Signed-off-by: Mark Brown <broonie@kernel.org>
---

diff --git a/drivers/spi/spi-hisi-kunpeng.c b/drivers/spi/spi-hisi-kunpeng.c
index 216a0a91fc47d..c42d2a2cdf1e4 100644
--- a/drivers/spi/spi-hisi-kunpeng.c
+++ b/drivers/spi/spi-hisi-kunpeng.c
@@ -196,8 +196,18 @@ static void hisi_spi_flush_fifo(struct hisi_spi *hs)
 	unsigned long limit = loops_per_jiffy << 1;
 
 	do {
-		while (hisi_spi_rx_not_empty(hs))
+		unsigned long inner_limit = loops_per_jiffy;
+
+		while (hisi_spi_rx_not_empty(hs) && --inner_limit) {
 			readl(hs->regs + HISI_SPI_DOUT);
+			cpu_relax();
+		}
+
+		if (!inner_limit) {
+			dev_warn_ratelimited(hs->dev, "RX FIFO flush timeout\n");
+			break;
+		}
+
 	} while (hisi_spi_busy(hs) && limit--);
 }