Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753570Ab3H0OcU (ORCPT ); Tue, 27 Aug 2013 10:32:20 -0400 Received: from mail-wg0-f42.google.com ([74.125.82.42]:52335 "EHLO mail-wg0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753041Ab3H0OcS (ORCPT ); Tue, 27 Aug 2013 10:32:18 -0400 MIME-Version: 1.0 In-Reply-To: References: <1373277884-3006-1-git-send-email-oleksandr.savchenko@ti.com> Date: Tue, 27 Aug 2013 07:32:17 -0700 Message-ID: Subject: Re: [PATCH] OMAP: UART: Keep the TX fifo full when possible From: Kevin Hilman To: gregkh@linuxfoundation.org Cc: jslaby@suse.cz, matts@commtech-fastcom.com, Paul McKenney , Santosh Shilimkar , David Howells , linux-serial@vger.kernel.org, LKML , linux-omap 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: 3294 Lines: 81 Greg, On Tue, Aug 20, 2013 at 8:57 AM, Kevin Hilman wrote: > + 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. Can this one be dropped from tty-next too until it can be investigated. The author's ti.com addresses are bouncing, and this has introduced a regression in -next. 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/