From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Boyd Subject: Re: [PATCH] serial: msm: Add magic SysRq support in dmmode Date: Wed, 29 Oct 2014 11:01:31 -0700 Message-ID: <54512B7B.905@codeaurora.org> References: <1414600712-20721-1-git-send-email-daniel.thompson@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: Received: from smtp.codeaurora.org ([198.145.11.231]:60876 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755513AbaJ2SBe (ORCPT ); Wed, 29 Oct 2014 14:01:34 -0400 In-Reply-To: <1414600712-20721-1-git-send-email-daniel.thompson@linaro.org> Sender: linux-arm-msm-owner@vger.kernel.org List-Id: linux-arm-msm@vger.kernel.org To: Daniel Thompson , 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 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. -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project