From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sekhar Nori Subject: Re: [PATCH] ARM: convert all "mov.* pc, reg" to "bx reg" for ARMv6+ Date: Wed, 2 Jul 2014 17:01:04 +0530 Message-ID: <53B3ED78.1070608@ti.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Andrew Lunn , , , Kevin Hilman , , Thierry Reding , , , Kukjin Kim , Herbert Xu , Stefano Stabellini , Magnus Damm , Gleb Natapov , Tony Lindgren , , Sebastian Hesselbarth , Jason Cooper , Stephen Warren , Marc Zyngier , Hans Ulli Kroll , Haojian Zhuang , Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: Errors-To: davinci-linux-open-source-bounces-VycZQUHpC/PFrsHnngEfi1aTQe2KTcn/@public.gmane.org List-Id: linux-crypto.vger.kernel.org On Tuesday 01 July 2014 09:28 PM, Russell King wrote: > ARMv6 and greater introduced a new instruction ("bx") which can be used > to return from function calls. Recent CPUs perform better when the > "bx lr" instruction is used rather than the "mov pc, lr" instruction, > and this sequence is strongly recommended to be used by the ARM > architecture manual (section A.4.1.1). > > We provide a new macro "ret" with all its variants for the condition > code which will resolve to the appropriate instruction. > > Rather than doing this piecemeal, and miss some instances, change all > the "mov pc" instances to use the new macro, with the exception of > the "movs" instruction and the kprobes code. This allows us to detect > the "mov pc, lr" case and fix it up - and also gives us the possibility > of deploying this for other registers depending on the CPU selection. > > Signed-off-by: Russell King > --- > arch/arm/mach-davinci/sleep.S | 2 +- I build, boot and suspend-to-RAM tested on DA850 which should exercise the path you modified. DaVinci devices are ARMv5 (ARM926) so the new bx instruction does not really get used. Acked-by: Sekhar Nori Thanks, Sekhar From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sekhar Nori Subject: Re: [PATCH] ARM: convert all "mov.* pc, reg" to "bx reg" for ARMv6+ Date: Wed, 2 Jul 2014 17:01:04 +0530 Message-ID: <53B3ED78.1070608@ti.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: Errors-To: davinci-linux-open-source-bounces-VycZQUHpC/PFrsHnngEfi1aTQe2KTcn/@public.gmane.org To: Russell King , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org Cc: Andrew Lunn , kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-sh-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Kevin Hilman , linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Thierry Reding , kvmarm-FPEHb7Xf0XXUo1n7N8X6UoWGPAHP3yOg@public.gmane.org, linux-samsung-soc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Kukjin Kim , Herbert Xu , Stefano Stabellini , Magnus Damm , Gleb Natapov , Tony Lindgren , xen-devel-GuqFBffKawtpuQazS67q72D2FQJk+8+b@public.gmane.org, Sebastian Hesselbarth , Jason Cooper , Stephen Warren , Marc Zyngier , Hans Ulli Kroll Haojian Zhuang List-Id: linux-omap@vger.kernel.org On Tuesday 01 July 2014 09:28 PM, Russell King wrote: > ARMv6 and greater introduced a new instruction ("bx") which can be used > to return from function calls. Recent CPUs perform better when the > "bx lr" instruction is used rather than the "mov pc, lr" instruction, > and this sequence is strongly recommended to be used by the ARM > architecture manual (section A.4.1.1). > > We provide a new macro "ret" with all its variants for the condition > code which will resolve to the appropriate instruction. > > Rather than doing this piecemeal, and miss some instances, change all > the "mov pc" instances to use the new macro, with the exception of > the "movs" instruction and the kprobes code. This allows us to detect > the "mov pc, lr" case and fix it up - and also gives us the possibility > of deploying this for other registers depending on the CPU selection. > > Signed-off-by: Russell King > --- > arch/arm/mach-davinci/sleep.S | 2 +- I build, boot and suspend-to-RAM tested on DA850 which should exercise the path you modified. DaVinci devices are ARMv5 (ARM926) so the new bx instruction does not really get used. Acked-by: Sekhar Nori Thanks, Sekhar From mboxrd@z Thu Jan 1 00:00:00 1970 From: nsekhar@ti.com (Sekhar Nori) Date: Wed, 2 Jul 2014 17:01:04 +0530 Subject: [PATCH] ARM: convert all "mov.* pc, reg" to "bx reg" for ARMv6+ In-Reply-To: References: Message-ID: <53B3ED78.1070608@ti.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tuesday 01 July 2014 09:28 PM, Russell King wrote: > ARMv6 and greater introduced a new instruction ("bx") which can be used > to return from function calls. Recent CPUs perform better when the > "bx lr" instruction is used rather than the "mov pc, lr" instruction, > and this sequence is strongly recommended to be used by the ARM > architecture manual (section A.4.1.1). > > We provide a new macro "ret" with all its variants for the condition > code which will resolve to the appropriate instruction. > > Rather than doing this piecemeal, and miss some instances, change all > the "mov pc" instances to use the new macro, with the exception of > the "movs" instruction and the kprobes code. This allows us to detect > the "mov pc, lr" case and fix it up - and also gives us the possibility > of deploying this for other registers depending on the CPU selection. > > Signed-off-by: Russell King > --- > arch/arm/mach-davinci/sleep.S | 2 +- I build, boot and suspend-to-RAM tested on DA850 which should exercise the path you modified. DaVinci devices are ARMv5 (ARM926) so the new bx instruction does not really get used. Acked-by: Sekhar Nori Thanks, Sekhar