Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752124AbaJQKZn (ORCPT ); Fri, 17 Oct 2014 06:25:43 -0400 Received: from mail-ob0-f177.google.com ([209.85.214.177]:51897 "EHLO mail-ob0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751293AbaJQKZm (ORCPT ); Fri, 17 Oct 2014 06:25:42 -0400 MIME-Version: 1.0 In-Reply-To: <543FBB97.9010006@hurleysoftware.com> References: <54369F77.5000906@hurleysoftware.com> <1413355395-5871-1-git-send-email-ssreedharan@mvista.com> <543FBB97.9010006@hurleysoftware.com> Date: Fri, 17 Oct 2014 15:55:41 +0530 Message-ID: Subject: Re: [PATCH] tty: serial: 8250_core: restore the LCR register in set_sleep From: Sudhir Sreedharan To: Peter Hurley Cc: Greg KH , Kevin Hilman , linux-serial@vger.kernel.org, Jiri Slaby , lkml , Olof Johansson , "linux-arm-kernel@lists.infradead.org" , Geert Uytterhoeven Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, On Thu, Oct 16, 2014 at 6:05 PM, Peter Hurley wrote: > 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. Yes, we can restore the LCR and EFR with the saved values. serial_out(p, UART_EFR, efr); serial_out(p, UART_LCR, lcr); I will send a new patch with the changes. Thanks, Sudhir > > 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/