linux-kernel - On 06/09/2014 04:59 PM, Aaro Koskinen wrote:> Hi,

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Date:	Mon,  9 Jun 2014 19:43:37 -0400
From:	Peter Hurley <peter@...leysoftware.com>
To:	Aaro Koskinen <aaro.koskinen@....fi>
Cc:	David Miller <davem@...emloft.net>, linux-kernel@...r.kernel.org,
	sparclinux@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Seth Bollinger <sethb@...i.com>,
	Peter Hurley <peter@...leysoftware.com>
Subject: On 06/09/2014 04:59 PM, Aaro Koskinen wrote:> Hi,

Thanks for the report Aaro.

Looks like Seth's fix exposes some broken assumptions in the Sun
serial drivers.

Can you test the patch below?

Regards,
Peter Hurley

PS - Do you have a way to test also your setup using hardware flow
control, ie. CRTSCTS?  I ask because I would expect that to be broken
even before Seth's patch.

--- %< ---
From: Peter Hurley <peter@...leysoftware.com>
Date: Mon, 9 Jun 2014 19:21:43 -0400
Subject: [PATCH] serial: sunsab: Test for no tx data on tx restart

Commit 717f3bbab3c7628736ef738fdbf3d9a28578c26c,
'serial_core: Fix conditional start_tx on ring buffer not empty'
exposes an incorrect assumption in sunsab's start_tx method; the
tx ring buffer can, in fact, be empty when restarting tx when
performing flow control.

Test for empty tx ring buffer when in sunsab's start_tx method.

Signed-off-by: Peter Hurley <peter@...leysoftware.com>
---
 drivers/tty/serial/sunsab.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/tty/serial/sunsab.c b/drivers/tty/serial/sunsab.c
index 5faa8e9..b99a4ea 100644
--- a/drivers/tty/serial/sunsab.c
+++ b/drivers/tty/serial/sunsab.c
@@ -427,6 +427,9 @@ static void sunsab_start_tx(struct uart_port *port)
 	struct circ_buf *xmit = &up->port.state->xmit;
 	int i;

+	if (uart_circ_empty(xmit))
+		return;
+
 	up->interrupt_mask1 &= ~(SAB82532_IMR1_ALLS|SAB82532_IMR1_XPR);
 	writeb(up->interrupt_mask1, &up->regs->w.imr1);

-- 
2.0.0

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