From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755137Ab1KIELU (ORCPT ); Tue, 8 Nov 2011 23:11:20 -0500 Received: from wolverine02.qualcomm.com ([199.106.114.251]:63509 "EHLO wolverine02.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751100Ab1KIELT (ORCPT ); Tue, 8 Nov 2011 23:11:19 -0500 X-IronPort-AV: E=McAfee;i="5400,1158,6524"; a="133591224" Message-ID: <4EB9FD65.3030900@codeaurora.org> Date: Tue, 08 Nov 2011 20:11:17 -0800 From: Stephen Boyd User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:7.0.1) Gecko/20110929 Thunderbird/7.0.1 MIME-Version: 1.0 To: Nicolas Pitre CC: David Brown , linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCHv3 2/2] msm: Support DEBUG_LL on MSM8660 and MSM8960 References: <1320777184-22446-1-git-send-email-sboyd@codeaurora.org> <1320777184-22446-3-git-send-email-sboyd@codeaurora.org> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/08/11 11:08, Nicolas Pitre wrote: >> + .macro senduart, rd, rx >> +#ifdef CONFIG_MSM_HAS_DEBUG_UART_HS >> + @ Write the 1 character to UARTDM_TF >> + str \rd, [\rx, #0x70] >> +#else >> teq \rx, #0 >> strne \rd, [\rx, #0x0C] >> +#endif >> .endm > Why testing for zero in the #else part? The upper level code should > never call this macro with a null byte. > Ok I poked into the git logs (thanks Bryan). It was first introduced in bcc0f6a ([ARM] msm: clean up iomap and devices, 2008-09-10). It seems that debug_ll support on MSM at the time had to remove the virtual mapping for the uart base. Thus when the MMU was enabled the addruart macro returned 0 and the senduart macro would test for 0 so that senduart could disable debug_ll when the MMU was enabled. Something about "problems with the peripheral window". Later on, the virtual mapping was added back in 6339f66 (msm: make debugging UART (for DEBUG_LL) configurable, 2009-11-02) but the patch forgot to remove the teq. So as it stands the teq has been useless for two years. -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.