Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752241AbaL2Oy0 (ORCPT ); Mon, 29 Dec 2014 09:54:26 -0500 Received: from mail-wi0-f182.google.com ([209.85.212.182]:53584 "EHLO mail-wi0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751440AbaL2OyX (ORCPT ); Mon, 29 Dec 2014 09:54:23 -0500 MIME-Version: 1.0 In-Reply-To: <1419827096.6184.128.camel@mtksdaap41> References: <1418891601-53769-1-git-send-email-eddie.huang@mediatek.com> <1418891601-53769-2-git-send-email-eddie.huang@mediatek.com> <1419827096.6184.128.camel@mtksdaap41> From: Rob Herring Date: Mon, 29 Dec 2014 08:54:02 -0600 Message-ID: Subject: Re: [PATCH 1/2] tty: serial: 8250_mtk: Add earlycon To: Eddie Huang Cc: Mark Rutland , Greg Kroah-Hartman , Matthias Brugger , srv_heupstream@mediatek.com, Rob Herring , Pawel Moll , Ian Campbell , Kumar Gala , Catalin Marinas , Will Deacon , Jiri Slaby , Alan Cox , "devicetree@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-serial@vger.kernel.org" , Sascha Hauer , Yingjoe Chen , yh.chen@mediatek.com Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Dec 28, 2014 at 10:24 PM, Eddie Huang wrote: > Hi Rob, > > On Fri, 2014-12-26 at 15:24 -0600, Rob Herring wrote: >> On Thu, Dec 18, 2014 at 2:33 AM, Eddie Huang wrote: >> > Mediatek UART has highspeed register, but 8250_early.c doesn't >> > support this, so add earlycon in 8250_mtk.c >> >> I don't see any highspeed register setup here. More generically, >> aren't you just skipping any UART setup? That may be useful on other >> platforms with 8250s, too. With the kernel command line version, you >> could perhaps add a "noinit" flag. The DT case is harder, and I'm not >> sure how we should handle that. We could perhaps add a >> "stdout-path-initialized" flag to chosen. >> > > Yes, I skipped UART setup same as msm_serial.c and amba-pl011.c > (although they are standalone serial driver). Just like earlyprintk, I > think earlycon should reuse UART setting in loader. Since some other > platforms with 8250 already depend on this, it's ok to add flags to > distinguish whether 8250 earlycon driver should init hw or not. As you > said, add "noinit" flag is simple, but "stdout-path-initialized" need > more discussion. > >> > >> > Signed-off-by: Eddie Huang >> > --- >> > drivers/tty/serial/8250/8250_mtk.c | 33 +++++++++++++++++++++++++++++++++ >> > 1 file changed, 33 insertions(+) >> > >> > diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c >> > index de7aae5..65dd569 100644 >> > --- a/drivers/tty/serial/8250/8250_mtk.c >> > +++ b/drivers/tty/serial/8250/8250_mtk.c >> > @@ -23,6 +23,7 @@ >> > #include >> > #include >> > #include >> > +#include >> > >> > #include "8250.h" >> > >> > @@ -289,6 +290,38 @@ static struct platform_driver mtk8250_platform_driver = { >> > }; >> > module_platform_driver(mtk8250_platform_driver); >> > >> > +#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE) >> > + >> > +static void __init mtk8250_serial_putc(struct uart_port *port, int c) >> > +{ >> > + while ((readl(port->membase + (UART_LSR << 2)) & BOTH_EMPTY) != >> > + BOTH_EMPTY) >> > + ; >> > + writel(c, port->membase + (UART_TX << 2)); >> > +} >> > + >> > +static void __init early_mtk8250_write(struct console *console, >> > + const char *s, unsigned int count) >> >> Is there a reason early_serial8250_write can't work for you other than >> it is currently static? >> >> Rob >> > > The reason is only static. I want to keep 8250_early.c untouchable, all > modifications in 8250_mtk.c That is not how kernel development works. You should fix 8250_early.c to do what you need rather than duplicating code. Rob -- 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/