From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Thu, 26 Mar 2015 16:09:14 +0100 (CET) Received: from mail.linuxfoundation.org ([140.211.169.12]:42075 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S27006155AbbCZPJMjhJ70 (ORCPT ); Thu, 26 Mar 2015 16:09:12 +0100 Received: from localhost (samsung-greg.rsr.lip6.fr [132.227.76.96]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 5C65BB12; Thu, 26 Mar 2015 15:09:05 +0000 (UTC) Date: Thu, 26 Mar 2015 16:09:01 +0100 From: Greg Kroah-Hartman To: James Hogan Cc: Ralf Baechle , linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, Jiri Slaby Subject: Re: [PATCH 7/9] tty: Add MIPS EJTAG Fast Debug Channel TTY driver Message-ID: <20150326150901.GA21726@kroah.com> References: <1422530054-7976-1-git-send-email-james.hogan@imgtec.com> <1422530054-7976-8-git-send-email-james.hogan@imgtec.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1422530054-7976-8-git-send-email-james.hogan@imgtec.com> User-Agent: Mutt/1.5.23 (2014-03-12) Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 46549 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: gregkh@linuxfoundation.org Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips On Thu, Jan 29, 2015 at 11:14:12AM +0000, James Hogan wrote: > Add TTY driver and consoles for the MIPS EJTAG Fast Debug Channel (FDC), > which is found on the per-CPU MIPS Common Device Mapped Memory (CDMM) > bus. > > The FDC is a per-CPU device which is used to communicate with an EJTAG > probe. RX and TX FIFOs exist, containing 32-bits of data and 4-bit > channel numbers. 16 general data streams are implemented on this for TTY > and console use by encoding up to 4 bytes on each 32-bit FDC word. > > The TTY devices are named e.g. /dev/ttyFDC3c2 for channel 2 of the FDC > attached to logical CPU 3. > > These can be used for getting the kernel log, a login prompt, or as a > GDB remote transport, all over EJTAG and without needing a serial port. > > It can have an interrupt to notify of when incoming data is available in > the RX FIFO or when the TX FIFO is no longer full. The detection of this > interrupt occurs in architecture / platform code, but it may be shared > with the timer and/or performance counter interrupt. > > Due to the per-CPU nature of the hardware, all outgoing TTY data is > written out from a kthread which is pinned to the appropriate CPU. > > The console is not bound to a specific CPU, so output will appear on the > chosen channel on whichever CPU the code is executing on. Enable with > e.g. console=fdc1 in kernel arguments. /dev/console is bound to the same > channel on the boot CPU's FDC if it exists. > > Signed-off-by: James Hogan > Cc: Ralf Baechle > Cc: Greg Kroah-Hartman > Cc: Jiri Slaby > Cc: linux-mips@linux-mips.org Acked-by: Greg Kroah-Hartman