From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 3332 invoked by alias); 19 May 2005 08:43:44 -0000 Mailing-List: contact ecos-discuss-help@ecos.sourceware.org; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: ecos-discuss-owner@ecos.sourceware.org Received: (qmail 3129 invoked from network); 19 May 2005 08:43:24 -0000 Received: from unknown (HELO anchor-post-31.mail.demon.net) (194.217.242.89) by sourceware.org with SMTP; 19 May 2005 08:43:24 -0000 Received: from calivar.demon.co.uk ([83.104.54.243] helo=xl5.calivar.com) by anchor-post-31.mail.demon.net with esmtp (Exim 4.42) id 1DYgZV-000Kn9-5h; Thu, 19 May 2005 08:40:01 +0000 Received: from xl5.calivar.com (localhost [127.0.0.1]) by xl5.calivar.com (Postfix) with ESMTP id 5552A3958C; Thu, 19 May 2005 09:43:22 +0100 (BST) To: droethig@cipher.com Cc: ecos-discuss@sources.redhat.com References: <428BCC08.8060804@cipher.com> From: Nick Garnett Original-Sender: nickg@ecoscentric.com Date: Thu, 19 May 2005 12:16:00 -0000 In-Reply-To: <428BCC08.8060804@cipher.com> Message-ID: User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Subject: Re: [ECOS] problem with generic serial driver? X-SW-Source: 2005-05/txt/msg00253.txt.bz2 David Roethig writes: > I am using (as of recently) the generic serial driver > package (16x5x compatible serial device drivers). > > The application was sending data to the port using the > file i/o interface: > > /* output string to serial port */ > err = cyg_io_write( serHandle, writeBuffer, length ); > > Nothing came out the serial port! That is, until, the app > output a 'diag_printf()'. That was a head-scratcher until > looking at the pc_serial_start_xmit() routine, I noticed > that the trasmitter wasn't being 'kicked' with a character > to the transmit register. > > // Enable the transmitter on the device > static void > pc_serial_start_xmit(serial_channel *chan) > { > pc_serial_info *ser_chan = (pc_serial_info *)chan->dev_priv; > cyg_addrword_t base = ser_chan->base; > cyg_uint8 _ier; > > HAL_READ_UINT8(base+REG_ier, _ier); > _ier |= IER_XMT; // Enable xmit interrupt > HAL_WRITE_UINT8(base+REG_ier, _ier); > > /* kick transmitter */ // **!! added !!** > (chan->callbacks->xmt_char)(chan); // **!! added !!** > } > > My questions: > 1) is the generic serial package still being used? > 2) is this a bug or are things configured incorrectly? This driver is being used on lots of targets, any that have 16x5x compatible serial devices will use it. However, not all devices that claim to be 16x5x compatible actually are. Some are missing features, some have extra features. Under normal circumstances the XMT interrupt occurs whenever the transmit buffer (or FIFO) is empty. That's why we have to enable and disable it, since we would otherwise be flooded with interrupts when we had nothing to transmit. It looks like your 16x5x clone either has this wrong, or, more likely, has a "transmit interrupt holdoff" feature in an attempt to solve the interrupt flood problem. Another example of hardware designers trying to be helpful but actually just making the software more complicated. Your fix is the correct thing to do, and is benign even for correctly functioning 16x5xs. Out of interest, what is the target you are working on? -- Nick Garnett eCos Kernel Architect http://www.ecoscentric.com The eCos and RedBoot experts -- Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss