ARM: 8383/1: nommu: avoid deprecated source register on mov

commit 970d96f9a81b0dd83ddd8bce0e5e1ba31881c5f5 upstream.

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.

Tested-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S
index cc176b67c13487b080bf7d1dc430314496a8b9b1..c6c66dd4be8992661d640c1a4885bcafe6b553db 100644 (file)
--- a/arch/arm/kernel/head-nommu.S
+++ b/arch/arm/kernel/head-nommu.S
@@ -77,13 +77,12 @@ 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
        adr     lr, BSYM(1f)                    @ return (PIC) address
  ARM(  add     pc, r10, #PROCINFO_INITFUNC     )
  THUMB(        add     r12, r10, #PROCINFO_INITFUNC    )
  THUMB(        ret     r12                             )
- 1:    b       __after_proc_init
+1:     bl      __after_proc_init
+       b       __mmap_switched
 ENDPROC(stext)
 
 #ifdef CONFIG_SMP
@@ -106,8 +105,7 @@ 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 +113,19 @@ ENTRY(secondary_startup)
        bl      __setup_mpu                     @ Initialize the MPU
 #endif
 
-       adr     lr, BSYM(__after_proc_init)     @ return address
-       mov     r13, r12                        @ __secondary_switched address
+       adr     lr, BSYM(1f)                    @ return (PIC) address
  ARM(  add     pc, r10, #PROCINFO_INITFUNC     )
  THUMB(        add     r12, r10, #PROCINFO_INITFUNC    )
  THUMB(        ret     r12                             )
-ENDPROC(secondary_startup)
-
-ENTRY(__secondary_switched)
+1:     bl      __after_proc_init
        ldr     sp, [r7, #8]                    @ 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 +158,7 @@ __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