@@ -883,7 +883,7 @@ auart_console_write(struct console *co, const char *str, unsigned int count)
struct mxs_auart_port *s;
struct uart_port *port;
unsigned int old_ctrl0, old_ctrl2;
- unsigned int to = 1000;
+ unsigned int to = 20000;
if (co->index >= MXS_AUART_PORTS || co->index < 0)
return;
@@ -904,18 +904,23 @@ auart_console_write(struct console *co, const char *str, unsigned int count)
uart_console_write(port, str, count, mxs_auart_console_putchar);
- /*
- * Finally, wait for transmitter to become empty
- * and restore the TCR
- */
+ /* Finally, wait for transmitter to become empty ... */
while (readl(port->membase + AUART_STAT) & AUART_STAT_BUSY) {
+ udelay(1);
if (!to--)
break;
- udelay(1);
}
- writel(old_ctrl0, port->membase + AUART_CTRL0);
- writel(old_ctrl2, port->membase + AUART_CTRL2);
+ /*
+ * ... and restore the TCR if we waited long enough for the transmitter
+ * to be idle. This might keep the transmitter enabled although it is
+ * unused, but that is better than to disable it while it is still
+ * transmitting.
+ */
+ if (!(readl(port->membase + AUART_STAT) & AUART_STAT_BUSY)) {
+ writel(old_ctrl0, port->membase + AUART_CTRL0);
+ writel(old_ctrl2, port->membase + AUART_CTRL2);
+ }
clk_disable(s->clk);
}
This is a note to let you know that I have just added a patch titled serial/mxs-auart: increase time to wait for transmitter to become to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue This patch is scheduled to be released in version 3.8.13.7. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.8.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From f953c2318ff358eb70aafcb70b56d7a119738179 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de> Date: Fri, 28 Jun 2013 11:49:41 +0200 Subject: serial/mxs-auart: increase time to wait for transmitter to become idle MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit 079a036f4283e2b0e5c26080b8c5112bc0cc1831 upstream. Without this patch the driver waits ~1 ms for the UART to become idle. At 115200n8 this time is (theoretically) enough to transfer 11.5 characters (= 115200 bits/s / (10 Bits/char) * 1ms). As the mxs-auart has a fifo size of 16 characters the clock is gated too early. The problem is worse for lower baud rates. This only happens to really shut down the transmitter in the middle of a transfer if /dev/ttyAPPx isn't opened in userspace (e.g. by a getty) but was at least once (because the bootloader doesn't disable the transmitter). So increase the timeout to 20 ms which should be enough for 9600n8, too. Moreover skip gating the clock if the timeout is elapsed. Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- drivers/tty/serial/mxs-auart.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) -- 1.8.1.2