linux-kernel - [PATCH v2] usb: chipidea: local_irq_save/restore added for hw_ep

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Message-ID: <20210817095313.GA671484@ubuntu>
Date:   Tue, 17 Aug 2021 18:53:13 +0900
From:   Jeaho Hwang <jhhwang@...t.co.kr>
To:     Peter Chen <peter.chen@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     tglx@...utronix.de, linux-rt-users@...r.kernel.org,
        team-linux@...t.co.kr, mkbyeon@...lectric.co.kr,
        khchoib@...lectric.co.kr
Subject: [PATCH v2] usb: chipidea: local_irq_save/restore added for
 hw_ep_prime

hw_ep_prime sometimes fails if irq occurs while it rus on RT kernel.
local_irq_save/restore is added inside the function to gurantee atomicity.
only effective for preempt_rt since hw_ep_prime is called inside top half
or spin_lock_irqsave. No effect is expected for standard linux.

Signed-off-by: Jeaho Hwang <jhhwang@...t.co.kr>

diff --git a/drivers/usb/chipidea/udc.c b/drivers/usb/chipidea/udc.c
index 8834ca613721..a624eddb3e22 100644
--- a/drivers/usb/chipidea/udc.c
+++ b/drivers/usb/chipidea/udc.c
@@ -191,22 +191,31 @@ static int hw_ep_get_halt(struct ci_hdrc *ci, int num, int dir)
 static int hw_ep_prime(struct ci_hdrc *ci, int num, int dir, int is_ctrl)
 {
 	int n = hw_ep_bit(num, dir);
+	unsigned long flags;
+	int ret = 0;
 
 	/* Synchronize before ep prime */
 	wmb();
 
-	if (is_ctrl && dir == RX && hw_read(ci, OP_ENDPTSETUPSTAT, BIT(num)))
+	/* irq affects this routine so irq should be disabled on RT.
+	 * on standard kernel, irq is already disabled by callers.
+	 */
+	local_irq_save(flags);
+	if (is_ctrl && dir == RX && hw_read(ci, OP_ENDPTSETUPSTAT, BIT(num))) {
+		local_irq_restore(flags);
 		return -EAGAIN;
+	}
 
 	hw_write(ci, OP_ENDPTPRIME, ~0, BIT(n));
 
 	while (hw_read(ci, OP_ENDPTPRIME, BIT(n)))
 		cpu_relax();
 	if (is_ctrl && dir == RX && hw_read(ci, OP_ENDPTSETUPSTAT, BIT(num)))
-		return -EAGAIN;
+		ret = -EAGAIN;
 
+	local_irq_restore(flags);
 	/* status shoult be tested according with manual but it doesn't work */
-	return 0;
+	return ret;
 }
 
 /**
-- 
2.25.1