From mboxrd@z Thu Jan 1 00:00:00 1970 From: Albert ARIBAUD Date: Fri, 29 Jan 2016 18:15:46 +0100 Subject: [U-Boot] [PATCH] arm: use common instructions applicable to armv7m & other arm archs In-Reply-To: <1453171978-30715-1-git-send-email-vikas.manocha@st.com> References: <1453171978-30715-1-git-send-email-vikas.manocha@st.com> Message-ID: <20160129181546.5e427a86@lilith> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Hello Vikas, On Mon, 18 Jan 2016 18:52:57 -0800, Vikas Manocha wrote: > BIC instruction to clear the SP is not allowed in armv7m & is deprecated > in ARMv6T2 & above. This patch cleans the code by using instructions allowed > for armv7m as well as other Arm archs. I am not against this patch, which has merits on its own; but the commit message above raises a couple of questions. 1. It seems to imply that in the current arch/arm/lib/crt0.S, BIC is incorrectly being used on sp. However, it is *not*; it is used on r3, precisely because it cannot be used directly on sp, as the comment before the bic instruction clearly states. Why does the commit message raise this non-issue? 2. I could not find any information on BIC being deprecated in Architecture Reference Manuals of either ArmV7 (section "Deprecated Features in ARMv7-M", or ARMv6-M (section "Deprecated and Obsolete Features"). Where does this information come from? Amicalement, -- Albert.