Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757608AbbEVXZz (ORCPT ); Fri, 22 May 2015 19:25:55 -0400 Received: from mail.kmu-office.ch ([178.209.48.109]:33684 "EHLO mail.kmu-office.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757371AbbEVXZx (ORCPT ); Fri, 22 May 2015 19:25:53 -0400 From: Stefan Agner To: linux@arm.linux.org.uk Cc: arnd@arndb.de, will.deacon@arm.com, u.kleine-koenig@pengutronix.de, manabian@gmail.com, mcoquelin.stm32@gmail.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Stefan Agner Subject: [PATCH v2] ARM: nommu: avoid deprecated source register on mov Date: Sat, 23 May 2015 01:25:48 +0200 Message-Id: <1432337148-9894-1-git-send-email-stefan@agner.ch> X-Mailer: git-send-email 2.4.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2954 Lines: 100 In Thumb2 mode, the stack register r13 is deprecated if the destination register is the program counter (r15). Similar to head.S, head-nommu.S uses r13 to store the return address used after configuring the CPU's CP15 register. However, since we do not enable a MMU, there will be no address switch and it is possible to use branch with link instruction to call __after_proc_init. Avoid using r13 completely by using bl to call __after_proc_init and get rid of __secondary_switched. Beside removing unnecessary complexity, this also fixes a compiler warning when compiling a !MMU kernel: Warning: Use of r13 as a source register is deprecated when r15 is the destination register. Suggested-by: Russell King Signed-off-by: Stefan Agner --- Changes in v2: - Load r7 outside CONFIG_ARM_MPU since its used outside later on arch/arm/kernel/head-nommu.S | 21 ++++++++------------- 1 file changed, 8 insertions(+), 13 deletions(-) diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S index c966016..9b8c5a1 100644 --- a/arch/arm/kernel/head-nommu.S +++ b/arch/arm/kernel/head-nommu.S @@ -77,13 +77,13 @@ ENTRY(stext) orr r6, r6, #(1 << MPU_RSR_EN) @ Set region enabled bit bl __setup_mpu #endif - ldr r13, =__mmap_switched @ address to jump to after - @ initialising sctlr + badr lr, 1f @ return (PIC) address ldr r12, [r10, #PROCINFO_INITFUNC] add r12, r12, r10 ret r12 - 1: b __after_proc_init +1: bl __after_proc_init + b __mmap_switched ENDPROC(stext) #ifdef CONFIG_SMP @@ -106,8 +106,7 @@ ENTRY(secondary_startup) movs r10, r5 @ invalid processor? beq __error_p @ yes, error 'p' - adr r4, __secondary_data - ldmia r4, {r7, r12} + ldr r7, __secondary_data #ifdef CONFIG_ARM_MPU /* Use MPU region info supplied by __cpu_up */ @@ -115,23 +114,19 @@ ENTRY(secondary_startup) bl __setup_mpu @ Initialize the MPU #endif - badr lr, __after_proc_init @ return address - mov r13, r12 @ __secondary_switched address + badr lr, 1f @ return (PIC) address ldr r12, [r10, #PROCINFO_INITFUNC] add r12, r12, r10 ret r12 -ENDPROC(secondary_startup) - -ENTRY(__secondary_switched) +1: bl __after_proc_init ldr sp, [r7, #12] @ set up the stack pointer mov fp, #0 b secondary_start_kernel -ENDPROC(__secondary_switched) +ENDPROC(secondary_startup) .type __secondary_data, %object __secondary_data: .long secondary_data - .long __secondary_switched #endif /* CONFIG_SMP */ /* @@ -164,7 +159,7 @@ __after_proc_init: #endif mcr p15, 0, r0, c1, c0, 0 @ write control reg #endif /* CONFIG_CPU_CP15 */ - ret r13 + ret lr ENDPROC(__after_proc_init) .ltorg -- 2.4.1 -- 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/