From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754477AbbBJJc1 (ORCPT ); Tue, 10 Feb 2015 04:32:27 -0500 Received: from www.linutronix.de ([62.245.132.108]:47411 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753544AbbBJJcZ (ORCPT ); Tue, 10 Feb 2015 04:32:25 -0500 Message-ID: <54D9D021.6000409@linutronix.de> Date: Tue, 10 Feb 2015 10:32:17 +0100 From: Sebastian Andrzej Siewior User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.4.0 MIME-Version: 1.0 To: Peter Hurley , Nicolas Schichan , linux-serial@vger.kernel.org CC: tony@atomide.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, balbi@ti.com, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 03/16] tty: serial: 8250_core: read only RX if there is something in the FIFO References: <1410377411-26656-1-git-send-email-bigeasy@linutronix.de> <1410377411-26656-4-git-send-email-bigeasy@linutronix.de> <54D8B772.1010405@freebox.fr> <54D9441B.7070403@hurleysoftware.com> In-Reply-To: <54D9441B.7070403@hurleysoftware.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/10/2015 12:34 AM, Peter Hurley wrote: > The "too much work" message means serial8250_handle_irq() is returning 0, > ie., not handled. Which in turn means IIR indicates no interrupt is pending > (UART_IIR_NO_INT == 1). The OMAP UART for instance have two possible TX-IRQ handling. The default is to fire the interrupt once there is room for at least one byte in the FIFO. I set the OMAP_UART_SCR_TX_EMPTY bit to get the same behavior as the 8250 driver expects (interrupt while the FIFO is empty). Without this bit set I've seen the message from time to time. Sebastian From mboxrd@z Thu Jan 1 00:00:00 1970 From: bigeasy@linutronix.de (Sebastian Andrzej Siewior) Date: Tue, 10 Feb 2015 10:32:17 +0100 Subject: [PATCH 03/16] tty: serial: 8250_core: read only RX if there is something in the FIFO In-Reply-To: <54D9441B.7070403@hurleysoftware.com> References: <1410377411-26656-1-git-send-email-bigeasy@linutronix.de> <1410377411-26656-4-git-send-email-bigeasy@linutronix.de> <54D8B772.1010405@freebox.fr> <54D9441B.7070403@hurleysoftware.com> Message-ID: <54D9D021.6000409@linutronix.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 02/10/2015 12:34 AM, Peter Hurley wrote: > The "too much work" message means serial8250_handle_irq() is returning 0, > ie., not handled. Which in turn means IIR indicates no interrupt is pending > (UART_IIR_NO_INT == 1). The OMAP UART for instance have two possible TX-IRQ handling. The default is to fire the interrupt once there is room for at least one byte in the FIFO. I set the OMAP_UART_SCR_TX_EMPTY bit to get the same behavior as the 8250 driver expects (interrupt while the FIFO is empty). Without this bit set I've seen the message from time to time. Sebastian