From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Hurley Subject: Re: [PATCH] tty: serial: 8250_core: restore the LCR register in set_sleep Date: Thu, 16 Oct 2014 08:35:35 -0400 Message-ID: <543FBB97.9010006@hurleysoftware.com> References: <54369F77.5000906@hurleysoftware.com> <1413355395-5871-1-git-send-email-ssreedharan@mvista.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1413355395-5871-1-git-send-email-ssreedharan@mvista.com> Sender: linux-kernel-owner@vger.kernel.org To: Sudhir Sreedharan , gregkh@linuxfoundation.org, khilman@kernel.org Cc: linux-serial@vger.kernel.org, jslaby@suse.cz, linux-kernel@vger.kernel.org, olof@lixom.net, linux-arm-kernel@lists.infradead.org, geert@linux-m68k.org List-Id: linux-serial@vger.kernel.org On 10/15/2014 02:43 AM, Sudhir Sreedharan wrote: > In ST16650V2 based serial uarts, while initalizing the PM state, > LCR registers are being initialized to 0 in serial8250_set_sleep(). > If console port is already initialized and being used, this will > throws garbage in the console. > > Signed-off-by: Sudhir Sreedharan > --- > drivers/tty/serial/8250/8250_core.c | 7 +++++-- > 1 files changed, 5 insertions(+), 2 deletions(-) > > diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c > index ca5cfdc..e054482 100644 > --- a/drivers/tty/serial/8250/8250_core.c > +++ b/drivers/tty/serial/8250/8250_core.c > @@ -595,6 +595,7 @@ static void serial8250_rpm_put_tx(struct uart_8250_port *p) > */ > static void serial8250_set_sleep(struct uart_8250_port *p, int sleep) > { > + unsigned char lcr, efr; > /* > * Exar UARTs have a SLEEP register that enables or disables > * each UART to enter sleep mode separately. On the XR17V35x the > @@ -611,6 +612,8 @@ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep) > > if (p->capabilities & UART_CAP_SLEEP) { > if (p->capabilities & UART_CAP_EFR) { > + lcr = serial_in(p, UART_LCR); > + efr = serial_in(p, UART_EFR); > serial_out(p, UART_LCR, UART_LCR_CONF_MODE_B); > serial_out(p, UART_EFR, UART_EFR_ECB); > serial_out(p, UART_LCR, 0); > @@ -618,8 +621,8 @@ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep) > serial_out(p, UART_IER, sleep ? UART_IERX_SLEEP : 0); > if (p->capabilities & UART_CAP_EFR) { > serial_out(p, UART_LCR, UART_LCR_CONF_MODE_B); > - serial_out(p, UART_EFR, 0); > - serial_out(p, UART_LCR, 0); > + serial_out(p, UART_EFR, sleep ? 0 : efr); > + serial_out(p, UART_LCR, sleep ? 0 : lcr); Why is it necessary to clear EFR and LCR here? Does the UART not power down? UARTs with CAP_SLEEP but not CAP_EFR don't clear LCR before sleep. However, if there is some kind of intentional side-effect here, then a comment should note that. Regards, Peter Hurley > } > } > out: > From mboxrd@z Thu Jan 1 00:00:00 1970 From: peter@hurleysoftware.com (Peter Hurley) Date: Thu, 16 Oct 2014 08:35:35 -0400 Subject: [PATCH] tty: serial: 8250_core: restore the LCR register in set_sleep In-Reply-To: <1413355395-5871-1-git-send-email-ssreedharan@mvista.com> References: <54369F77.5000906@hurleysoftware.com> <1413355395-5871-1-git-send-email-ssreedharan@mvista.com> Message-ID: <543FBB97.9010006@hurleysoftware.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 10/15/2014 02:43 AM, Sudhir Sreedharan wrote: > In ST16650V2 based serial uarts, while initalizing the PM state, > LCR registers are being initialized to 0 in serial8250_set_sleep(). > If console port is already initialized and being used, this will > throws garbage in the console. > > Signed-off-by: Sudhir Sreedharan > --- > drivers/tty/serial/8250/8250_core.c | 7 +++++-- > 1 files changed, 5 insertions(+), 2 deletions(-) > > diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c > index ca5cfdc..e054482 100644 > --- a/drivers/tty/serial/8250/8250_core.c > +++ b/drivers/tty/serial/8250/8250_core.c > @@ -595,6 +595,7 @@ static void serial8250_rpm_put_tx(struct uart_8250_port *p) > */ > static void serial8250_set_sleep(struct uart_8250_port *p, int sleep) > { > + unsigned char lcr, efr; > /* > * Exar UARTs have a SLEEP register that enables or disables > * each UART to enter sleep mode separately. On the XR17V35x the > @@ -611,6 +612,8 @@ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep) > > if (p->capabilities & UART_CAP_SLEEP) { > if (p->capabilities & UART_CAP_EFR) { > + lcr = serial_in(p, UART_LCR); > + efr = serial_in(p, UART_EFR); > serial_out(p, UART_LCR, UART_LCR_CONF_MODE_B); > serial_out(p, UART_EFR, UART_EFR_ECB); > serial_out(p, UART_LCR, 0); > @@ -618,8 +621,8 @@ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep) > serial_out(p, UART_IER, sleep ? UART_IERX_SLEEP : 0); > if (p->capabilities & UART_CAP_EFR) { > serial_out(p, UART_LCR, UART_LCR_CONF_MODE_B); > - serial_out(p, UART_EFR, 0); > - serial_out(p, UART_LCR, 0); > + serial_out(p, UART_EFR, sleep ? 0 : efr); > + serial_out(p, UART_LCR, sleep ? 0 : lcr); Why is it necessary to clear EFR and LCR here? Does the UART not power down? UARTs with CAP_SLEEP but not CAP_EFR don't clear LCR before sleep. However, if there is some kind of intentional side-effect here, then a comment should note that. Regards, Peter Hurley > } > } > out: >