[PATCH] tty: serial: fixed uart irq maybe cause irq storm

[fengchunguo@xxxxxxx]

From: "chunguo.feng" <chunguo.feng@xxxxxxxxxxxxx>

if not disable uart irq before disable clk,  uart irq maybe triggered after
disabled clk immediately, then maybe cause irq storm.

Reproduced the below call trace, see i2c not be connected, but irq storm
was triggered.

i2c_designware 30b70000.i2c: controller timed out
CPU: 2 PID: 2932 Comm: gnss@1.0-servic 
Tainted: G O 5.14.61-00094-geaa0149416cc-dirty #8
Hardware name: Semidrive kunlun x9 REF Board (DT)
Call trace:
[<ffff00000808a3cc>] dump_backtrace+0x0/0x3c0
[<ffff00000808a7a0>] show_stack+0x14/0x1c
[<ffff000008cef43c>] dump_stack+0xc4/0xfc
[<ffff00000814eb80>] __report_bad_irq+0x50/0xe0
[<ffff00000814eaec>] note_interrupt+0x248/0x28c
[<ffff00000814c0e8>] handle_irq_event+0x78/0xa4
[<ffff00000814fcb8>] handle_fasteoi_irq+0xe4/0x1b4
[<ffff00000814b060>] __handle_domain_irq+0x7c/0xbc
[<ffff00000808176c>] gic_handle_irq+0x4c/0xb8
[<ffff000008083230>] el1_irq+0xb0/0x124
[<ffff000008d09f5c>] _raw_spin_unlock_irqrestore+0x10/0x44
[<ffff00000865b784>] dw8250_set_termios+0x48/0xf4
[<ffff0000086545a4>] serial8250_set_termios+0x14/0x28
[<ffff00000864c4f4>] uart_change_speed+0x38/0x10c
[<ffff00000864e458>] uart_set_termios+0xd0/0x17c
[<ffff000008630ad4>] tty_set_termios+0x160/0x1e4
[<ffff00000863165c>] set_termios+0x32c/0x3bc
[<ffff000008631248>] tty_mode_ioctl+0x6f0/0x7d8
[<ffff000008631a6c>] n_tty_ioctl_helper+0x10c/0x1e8
[<ffff00000862d2c4>] n_tty_ioctl+0x120/0x194
[<ffff00000862a724>] tty_ioctl+0x658/0xa34
[<ffff0000082a8f40>] do_vfs_ioctl+0x554/0x810
[<ffff0000082a9368>] SyS_ioctl+0x88/0x94
Exception stack(0xffff00000ccf3ec0 to 0xffff00000ccf4000

Signed-off-by: chunguo.feng <chunguo.feng@xxxxxxxxxxxxx>
---
 drivers/tty/serial/8250/8250_dw.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index c1d43f0..133c24e 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -359,6 +359,12 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios,
 
 	rate = clk_round_rate(d->clk, newrate);
 	if (rate > 0 && p->uartclk != rate) {
+		/*Need disable uart irq before disabled clk, because uart irq maybe triggered after
+		 * disabled clk immediately, then cause irq storm.
+		 */
+		if (p->irq)
+			disabled_irq(p->irq);
+
 		clk_disable_unprepare(d->clk);
 		/*
 		 * Note that any clock-notifer worker will block in
@@ -368,6 +374,9 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios,
 		if (!ret)
 			p->uartclk = rate;
 		clk_prepare_enable(d->clk);
+
+		if (p->irq)
+			enable_irq(p->irq);
 	}
 
 	dw8250_do_set_termios(p, termios, old);
-- 
2.7.4