Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752246AbaJPMfr (ORCPT ); Thu, 16 Oct 2014 08:35:47 -0400 Received: from mailout32.mail01.mtsvc.net ([216.70.64.70]:42716 "EHLO n23.mail01.mtsvc.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751177AbaJPMfp (ORCPT ); Thu, 16 Oct 2014 08:35:45 -0400 Message-ID: <543FBB97.9010006@hurleysoftware.com> Date: Thu, 16 Oct 2014 08:35:35 -0400 From: Peter Hurley User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.2 MIME-Version: 1.0 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 Subject: Re: [PATCH] tty: serial: 8250_core: restore the LCR register in set_sleep References: <54369F77.5000906@hurleysoftware.com> <1413355395-5871-1-git-send-email-ssreedharan@mvista.com> In-Reply-To: <1413355395-5871-1-git-send-email-ssreedharan@mvista.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit 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 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: > -- 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/