From mboxrd@z Thu Jan 1 00:00:00 1970 From: richard.genoud@gmail.com (Richard Genoud) Date: Mon, 20 Mar 2017 11:33:30 +0100 Subject: [RFC PATCH] tty/serial: atmel: fix TX path in atmel_console_write() In-Reply-To: <20170315152948.10978-1-nicolas.ferre@microchip.com> References: <20170315152948.10978-1-nicolas.ferre@microchip.com> Message-ID: <05f5c67b-67d8-02b4-e170-52f2484d0927@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 15/03/2017 16:29, Nicolas Ferre wrote: > A side effect of 89d8232411a8 ("tty/serial: atmel_serial: BUG: stop DMA > from transmitting in stop_tx") is that the console can be called with > TX path disabled. Then the system would hang trying to push charecters > out in atmel_console_putchar(). > > Signed-off-by: Nicolas Ferre > Fixes: 89d8232411a8 ("tty/serial: atmel_serial: BUG: stop DMA from transmitting > in stop_tx") > Cc: stable # 4.4+ > --- > Hi Richard, > > I found this to fix the problem with system hang in my linux-4.4-at91 branch > (in the atmel_console_putchar() waiting loop actually). I'm open to more > insignt. > As we cannot figure out if this bit is set or not, I didn't preserve the > current status... > > Regards, > > drivers/tty/serial/atmel_serial.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c > index dcebb28ffbc4..7372dbdb7a4c 100644 > --- a/drivers/tty/serial/atmel_serial.c > +++ b/drivers/tty/serial/atmel_serial.c > @@ -2483,6 +2483,9 @@ static void atmel_console_write(struct console *co, const char *s, u_int count) > pdc_tx = atmel_uart_readl(port, ATMEL_PDC_PTSR) & ATMEL_PDC_TXTEN; > atmel_uart_writel(port, ATMEL_PDC_PTCR, ATMEL_PDC_TXTDIS); > > + /* Make sure that tx path is actually able to send characters */ > + atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN); > + > uart_console_write(port, s, count, atmel_console_putchar); > > /* > Acked-by: Richard Genoud