Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751866AbaGFPao (ORCPT ); Sun, 6 Jul 2014 11:30:44 -0400 Received: from mailout32.mail01.mtsvc.net ([216.70.64.70]:33818 "EHLO n23.mail01.mtsvc.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751138AbaGFPaM (ORCPT ); Sun, 6 Jul 2014 11:30:12 -0400 From: Peter Hurley To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, Peter Hurley , Seth Bollinger , "David S. Miller" , Sam Ravnborg , Thomas Bogendoerfer Subject: [PATCH 1/2] serial: Test for no tx data on tx restart Date: Sun, 6 Jul 2014 11:29:52 -0400 Message-Id: <1404660593-12172-2-git-send-email-peter@hurleysoftware.com> X-Mailer: git-send-email 2.0.0 In-Reply-To: <1404660593-12172-1-git-send-email-peter@hurleysoftware.com> References: <20140609205917.GA913@drone.musicnaut.iki.fi> <1404660593-12172-1-git-send-email-peter@hurleysoftware.com> X-Authenticated-User: 990527 peter@hurleysoftware.com X-MT-ID: 8FA290C2A27252AACF65DBC4A42F3CE3735FB2A4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit 717f3bbab3c7628736ef738fdbf3d9a28578c26c, 'serial_core: Fix conditional start_tx on ring buffer not empty' exposes an incorrect assumption in several drivers' start_tx methods; the tx ring buffer can, in fact, be empty when restarting tx while performing flow control. Affected drivers: sunsab.c ip22zilog.c pmac_zilog.c sunzilog.c m32r_sio.c imx.c Other in-tree serial drivers either are not affected or already test for empty tx ring buffer before transmitting. Test for empty tx ring buffer in start_tx() method, after transmitting x_char (if applicable). Reported-by: Aaro Koskinen Cc: Seth Bollinger Cc: "David S. Miller" Cc: Sam Ravnborg Cc: Thomas Bogendoerfer Signed-off-by: Peter Hurley --- drivers/tty/serial/imx.c | 3 +++ drivers/tty/serial/ip22zilog.c | 2 ++ drivers/tty/serial/m32r_sio.c | 8 +++++--- drivers/tty/serial/pmac_zilog.c | 3 +++ drivers/tty/serial/sunsab.c | 3 +++ drivers/tty/serial/sunzilog.c | 2 ++ 6 files changed, 18 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 3b6c1a2..23c1dae 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -563,6 +563,9 @@ static void imx_start_tx(struct uart_port *port) struct imx_port *sport = (struct imx_port *)port; unsigned long temp; + if (uart_circ_empty(&port.state->xmit)) + return; + if (USE_IRDA(sport)) { /* half duplex in IrDA mode; have to disable receive mode */ temp = readl(sport->port.membase + UCR4); diff --git a/drivers/tty/serial/ip22zilog.c b/drivers/tty/serial/ip22zilog.c index 1efd4c3..99b7b86 100644 --- a/drivers/tty/serial/ip22zilog.c +++ b/drivers/tty/serial/ip22zilog.c @@ -603,6 +603,8 @@ static void ip22zilog_start_tx(struct uart_port *port) } else { struct circ_buf *xmit = &port->state->xmit; + if (uart_circ_empty(xmit)) + return; writeb(xmit->buf[xmit->tail], &channel->data); ZSDELAY(); ZS_WSYNC(channel); diff --git a/drivers/tty/serial/m32r_sio.c b/drivers/tty/serial/m32r_sio.c index 68f2c53..5702828 100644 --- a/drivers/tty/serial/m32r_sio.c +++ b/drivers/tty/serial/m32r_sio.c @@ -266,9 +266,11 @@ static void m32r_sio_start_tx(struct uart_port *port) if (!(up->ier & UART_IER_THRI)) { up->ier |= UART_IER_THRI; serial_out(up, UART_IER, up->ier); - serial_out(up, UART_TX, xmit->buf[xmit->tail]); - xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1); - up->port.icount.tx++; + if (!uart_circ_empty(xmit)) { + serial_out(up, UART_TX, xmit->buf[xmit->tail]); + xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1); + up->port.icount.tx++; + } } while((serial_in(up, UART_LSR) & UART_EMPTY) != UART_EMPTY); #else diff --git a/drivers/tty/serial/pmac_zilog.c b/drivers/tty/serial/pmac_zilog.c index 8193635..f7ad5b9 100644 --- a/drivers/tty/serial/pmac_zilog.c +++ b/drivers/tty/serial/pmac_zilog.c @@ -653,6 +653,8 @@ static void pmz_start_tx(struct uart_port *port) } else { struct circ_buf *xmit = &port->state->xmit; + if (uart_circ_empty(xmit)) + goto out; write_zsdata(uap, xmit->buf[xmit->tail]); zssync(uap); xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1); @@ -661,6 +663,7 @@ static void pmz_start_tx(struct uart_port *port) if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) uart_write_wakeup(&uap->port); } + out: pmz_debug("pmz: start_tx() done.\n"); } diff --git a/drivers/tty/serial/sunsab.c b/drivers/tty/serial/sunsab.c index 80a58ec..2f57df9 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); diff --git a/drivers/tty/serial/sunzilog.c b/drivers/tty/serial/sunzilog.c index a85db8b..02df394 100644 --- a/drivers/tty/serial/sunzilog.c +++ b/drivers/tty/serial/sunzilog.c @@ -703,6 +703,8 @@ static void sunzilog_start_tx(struct uart_port *port) } else { struct circ_buf *xmit = &port->state->xmit; + if (uart_circ_empty(xmit)) + return; writeb(xmit->buf[xmit->tail], &channel->data); ZSDELAY(); ZS_WSYNC(channel); -- 2.0.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/