Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933375AbaJ3MBF (ORCPT ); Thu, 30 Oct 2014 08:01:05 -0400 Received: from mail-wg0-f53.google.com ([74.125.82.53]:52742 "EHLO mail-wg0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933133AbaJ3MBD (ORCPT ); Thu, 30 Oct 2014 08:01:03 -0400 X-Greylist: delayed 2085 seconds by postgrey-1.27 at vger.kernel.org; Thu, 30 Oct 2014 08:01:02 EDT Message-ID: <54522874.6040901@linaro.org> Date: Thu, 30 Oct 2014 12:00:52 +0000 From: Daniel Thompson User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: Stephen Boyd , Greg Kroah-Hartman CC: David Brown , Daniel Walker , Bryan Huntsman , Jiri Slaby , linux-arm-msm@vger.kernel.org, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, patches@linaro.org, linaro-kernel@lists.linaro.org, John Stultz , Sumit Semwal Subject: Re: [PATCH] serial: msm: Add magic SysRq support in dmmode References: <1414600712-20721-1-git-send-email-daniel.thompson@linaro.org> <54512B7B.905@codeaurora.org> In-Reply-To: <54512B7B.905@codeaurora.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 29/10/14 18:01, Stephen Boyd wrote: > On 10/29/2014 09:38 AM, Daniel Thompson wrote: >> Currently the _dm RX handler detects breaks but does not pass any >> characters to uart_handle_sysrq_char(). >> >> The _dm optimizations combined with the port's spin lock make if >> difficult to pass all characters to the sysrq logic because we cannot >> safely call uart_handle_sysrq_char() when the lock is held without >> deadlock (the console handler also takes the lock). >> >> Rather than passing all characters via uart_handle_sysrq_char() this patch >> only passes the last few characters in the FIFO. This should include all >> characters typed as a slow (human) rate. This makes the problem much >> simpler and allows us to move the handling of these characters outside >> of the port lock. This makes magic SysRq work if there is a human at >> the keyboard (or a short delay in a script). >> >> Signed-off-by: Daniel Thompson >> --- > > I have a patch that I was going to send for this (Frank R. and I have > been looking at it since a month or two ago). This patch doesn't look > correct given that the SR register is not actually accurate and doesn't > indicate that a break is there in the fifo. I'll Cc you on the patch, > please test it. Testing on IFC6410 is mostly OK. Most sysrq actions work fine but resume from kdb is extremely unreliable; in most cases is kills the serial RX ('echo g > /proc/sysrq-trigger' shows that characters are still going into the FIFO but never get to the interrupt handler). However, this is not a regression versus my patch, resume was not reliable with my patch either. -- 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/