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From: Du Huanpeng <u74147@gmail.com>
To: barebox@lists.infradead.org
Cc: Du Huanpeng <u74147@gmail.com>
Subject: [PATCH] MIPS: asm/debug_ll_ns16550.h: add nop in delay slot
Date: Tue,  8 Sep 2020 14:25:05 +0800	[thread overview]
Message-ID: <1599546305-10121-1-git-send-email-u74147@gmail.com> (raw)

In the debug_ll_outc_a0 macro, a0 is written to the uart data
register many times in a delay slot when the uart is not ready
to send data. insert a nop to avoid this.

Signed-off-by: Du Huanpeng <u74147@gmail.com>
---
 arch/mips/include/asm/debug_ll_ns16550.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/mips/include/asm/debug_ll_ns16550.h b/arch/mips/include/asm/debug_ll_ns16550.h
index df58c4c..cf666d1 100644
--- a/arch/mips/include/asm/debug_ll_ns16550.h
+++ b/arch/mips/include/asm/debug_ll_ns16550.h
@@ -88,6 +88,7 @@ static inline void PUTC_LL(char ch)
 201:	lbu	t1, UART_LSR(t0)	/* get line status */
 	andi	t1, t1, UART_LSR_THRE	/* check for transmitter empty */
 	beqz	t1, 201b			/* try again */
+	nop
 
 	sb	a0, UART_THR(t0)	/* write the character */
 
-- 
2.7.4


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             reply	other threads:[~2020-09-08  6:25 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-08  6:25 Du Huanpeng [this message]
2020-09-08 11:39 ` Antony Pavlov

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