Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753765AbbF3N6i (ORCPT ); Tue, 30 Jun 2015 09:58:38 -0400 Received: from foss.arm.com ([217.140.101.70]:41741 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753141AbbF3N6V (ORCPT ); Tue, 30 Jun 2015 09:58:21 -0400 Date: Tue, 30 Jun 2015 14:58:15 +0100 From: Will Deacon To: Timur Tabi Cc: "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Shanker Donthineni , "awallis@codeaurora.org" , "abhimany@codeaurora.org" , "sboyd@codeaurora.org" , Vipul Gandhi Subject: Re: [PATCH 1/3] hvc_dcc: bind driver to core0 for reads and writes Message-ID: <20150630135815.GK27725@arm.com> References: <1435344756-20901-1-git-send-email-timur@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1435344756-20901-1-git-send-email-timur@codeaurora.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1240 Lines: 26 On Fri, Jun 26, 2015 at 07:52:34PM +0100, Timur Tabi wrote: > Some debuggers, such as Trace32 from Lauterbach GmbH, do not handle > reads/writes from/to DCC on secondary cores. Each core has its > own DCC device registers, so when a core reads or writes from/to DCC, > it only accesses its own DCC device. Since kernel code can run on > any core, every time the kernel wants to write to the console, it > might write to a different DCC. > > In SMP mode, Trace32 only uses the DCC on core 0. In AMP mode, it > creates multiple windows, and each window shows the DCC output > only from that core's DCC. The result is that console output is > either lost or scattered across windows. > > Selecting this option will enable code that serializes all console > input and output to core 0. The DCC driver will create input and > output FIFOs that all cores will use. Reads and writes from/to DCC > are handled by a workqueue that runs only core 0. What happens if CPU0 is hotplugged off? Will -- 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/