Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751782Ab3HTP52 (ORCPT ); Tue, 20 Aug 2013 11:57:28 -0400 Received: from mail-wg0-f48.google.com ([74.125.82.48]:49983 "EHLO mail-wg0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751097Ab3HTP51 (ORCPT ); Tue, 20 Aug 2013 11:57:27 -0400 MIME-Version: 1.0 In-Reply-To: <1373277884-3006-1-git-send-email-oleksandr.savchenko@ti.com> References: <1373277884-3006-1-git-send-email-oleksandr.savchenko@ti.com> Date: Tue, 20 Aug 2013 08:57:25 -0700 Message-ID: Subject: Re: [PATCH] OMAP: UART: Keep the TX fifo full when possible From: Kevin Hilman To: Alexander Savchenko Cc: gregkh@linuxfoundation.org, jslaby@suse.cz, matts@commtech-fastcom.com, Paul McKenney , Santosh Shilimkar , dhowells@redhat.com, linux-serial@vger.kernel.org, LKML Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2980 Lines: 77 + Felipe On Mon, Jul 8, 2013 at 3:04 AM, Alexander Savchenko wrote: > From: Dmitry Fink > > Current logic results in interrupt storm since the fifo > is constantly below the threshold level. Change the logic > to fill all the available spaces in the fifo as long as > we have data to minimize the possibilty of underflow and > elimiate excessive interrupts. > > Signed-off-by: Dmitry Fink > Signed-off-by: Alexander Savchenko Hmm, another OMAP serial patch that wasn't Cc'd to linux-omap where OMAP users might have seen it. :( I just bisected a strange problem in linux-next on OMAP3 down to this patch. Reverting it fixes the problem. On OMAP3530 Beagle and Overo, after boot, doing a 'cat /proc/cpuinfo' was not returning to a prompt, suggesting something strange with the FIFO. Hitting return gets me back to a prompt. Greg, this one should also be dropped from tty-next until it can be further investgated and the problem solved. Thanks, Kevin > --- > drivers/tty/serial/omap-serial.c | 3 ++- > include/uapi/linux/serial_reg.h | 1 + > 2 files changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c > index b6d1728..5c9b074 100644 > --- a/drivers/tty/serial/omap-serial.c > +++ b/drivers/tty/serial/omap-serial.c > @@ -310,7 +310,8 @@ static void transmit_chars(struct uart_omap_port *up, unsigned int lsr) > serial_omap_stop_tx(&up->port); > return; > } > - count = up->port.fifosize / 4; > + count = up->port.fifosize - > + (serial_in(up, UART_OMAP_TXFIFO_LVL) & 0xFF); > do { > serial_out(up, UART_TX, xmit->buf[xmit->tail]); > xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1); > diff --git a/include/uapi/linux/serial_reg.h b/include/uapi/linux/serial_reg.h > index e632260..97c26be 100644 > --- a/include/uapi/linux/serial_reg.h > +++ b/include/uapi/linux/serial_reg.h > @@ -366,6 +366,7 @@ > #define UART_OMAP_MDR1_FIR_MODE 0x05 /* FIR mode */ > #define UART_OMAP_MDR1_CIR_MODE 0x06 /* CIR mode */ > #define UART_OMAP_MDR1_DISABLE 0x07 /* Disable (default state) */ > +#define UART_OMAP_TXFIFO_LVL 0x1A /* TX FIFO fullness */ > > /* > * These are definitions for the Exar XR17V35X and XR17(C|D)15X > -- > 1.7.9.5 > > -- > 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/ -- 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/