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Message-Id: <20091217011603.362701500@mini.kroah.org>
Date: Wed, 16 Dec 2009 17:14:53 -0800
From: Greg KH <gregkh@...e.de>
To: linux-kernel@...r.kernel.org, stable@...nel.org
Cc: stable-review@...nel.org, torvalds@...ux-foundation.org,
akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
Ian Jackson <ian.jackson@...citrix.com>,
Alan Cox <alan@...ux.intel.com>
Subject: [42/90] Serial: Do not read IIR in serial8250_start_tx when UART_BUG_TXEN
2.6.31-stable review patch. If anyone has any objections, please let us know.
------------------
From: Ian Jackson <ian.jackson@...citrix.com>
commit 68cb4f8e246bbbc649980be0628cae9265870a91 upstream.
Do not read IIR in serial8250_start_tx when UART_BUG_TXEN
Reading the IIR clears some oustanding interrupts so it is not safe.
Instead, simply transmit immediately if the buffer is empty without
regard to IIR.
Signed-off-by: Ian Jackson <ian.jackson@...citrix.com>
Reviewed-by: Markus Armbruster <armbru@...hat.com>
Reviewed-by: Jiri Kosina <jkosina@...e.cz>
Cc: Alan Cox <alan@...ux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
drivers/serial/8250.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -1337,14 +1337,12 @@ static void serial8250_start_tx(struct u
serial_out(up, UART_IER, up->ier);
if (up->bugs & UART_BUG_TXEN) {
- unsigned char lsr, iir;
+ unsigned char lsr;
lsr = serial_in(up, UART_LSR);
up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
- iir = serial_in(up, UART_IIR) & 0x0f;
if ((up->port.type == PORT_RM9000) ?
- (lsr & UART_LSR_THRE &&
- (iir == UART_IIR_NO_INT || iir == UART_IIR_THRI)) :
- (lsr & UART_LSR_TEMT && iir & UART_IIR_NO_INT))
+ (lsr & UART_LSR_THRE) :
+ (lsr & UART_LSR_TEMT))
transmit_chars(up);
}
}
--
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