From mboxrd@z Thu Jan 1 00:00:00 1970 From: lorenzo.pieralisi@arm.com (Lorenzo Pieralisi) Date: Thu, 18 Feb 2016 11:41:27 +0000 Subject: [PATCH v5 11/15] arm64: head.S: Change the register el2_setup() returns its result in x0 In-Reply-To: <1455637767-31561-12-git-send-email-james.morse@arm.com> References: <1455637767-31561-1-git-send-email-james.morse@arm.com> <1455637767-31561-12-git-send-email-james.morse@arm.com> Message-ID: <20160218114127.GA12626@red-moon> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi James, On Tue, Feb 16, 2016 at 03:49:23PM +0000, James Morse wrote: > Today el2_setup() returns its result in w20. This means we can't call it > like any normal function. Change this to w0. > > All three callers of el2_setup() call set_cpu_boot_mode_flag() immediately > afterwards, and don't rely on x0 in later code. Boot cpu code calls > preserve_boot_args() before el2_setup(), so we don't clobber the DT pointer. > > Signed-off-by: James Morse > --- > arch/arm64/include/asm/processor.h | 2 ++ > arch/arm64/kernel/head.S | 18 +++++++++--------- > 2 files changed, 11 insertions(+), 9 deletions(-) > > diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h > index 4acb7ca94fcd..07ac4351538e 100644 > --- a/arch/arm64/include/asm/processor.h > +++ b/arch/arm64/include/asm/processor.h > @@ -188,4 +188,6 @@ static inline void spin_lock_prefetch(const void *x) > > void cpu_enable_pan(void *__unused); > > +int el2_setup(void); Do we really need to have this declaration (and this patch) ? We never treat (and call) el2_setup as a C function anyway, as long as the registers used to pass in values (and return value) are documented I do not think we have an issue anyway, am I missing something here ? Thanks, Lorenzo > + > #endif /* __ASM_PROCESSOR_H */ > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index 410a2dc04775..5894c7e91e6b 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -206,7 +206,7 @@ section_table: > > ENTRY(stext) > bl preserve_boot_args > - bl el2_setup // Drop to EL1, w20=cpu_boot_mode > + bl el2_setup // Drop to EL1, w0=cpu_boot_mode > adrp x24, __PHYS_OFFSET > bl set_cpu_boot_mode_flag > bl __create_page_tables // x25=TTBR0, x26=TTBR1 > @@ -446,8 +446,8 @@ ENDPROC(__mmap_switched) > * If we're fortunate enough to boot at EL2, ensure that the world is > * sane before dropping to EL1. > * > - * Returns either BOOT_CPU_MODE_EL1 or BOOT_CPU_MODE_EL2 in x20 if > - * booted in EL1 or EL2 respectively. > + * Returns either BOOT_CPU_MODE_EL1 or BOOT_CPU_MODE_EL2 if booted in > + * EL1 or EL2 respectively. > */ > ENTRY(el2_setup) > mrs x0, CurrentEL > @@ -462,7 +462,7 @@ CPU_LE( bic x0, x0, #(1 << 25) ) // Clear the EE bit for EL2 > CPU_BE( orr x0, x0, #(3 << 24) ) // Set the EE and E0E bits for EL1 > CPU_LE( bic x0, x0, #(3 << 24) ) // Clear the EE and E0E bits for EL1 > msr sctlr_el1, x0 > - mov w20, #BOOT_CPU_MODE_EL1 // This cpu booted in EL1 > + mov w0, #BOOT_CPU_MODE_EL1 // This cpu booted in EL1 > isb > ret > > @@ -538,20 +538,20 @@ CPU_LE( movk x0, #0x30d0, lsl #16 ) // Clear EE and E0E on LE systems > PSR_MODE_EL1h) > msr spsr_el2, x0 > msr elr_el2, lr > - mov w20, #BOOT_CPU_MODE_EL2 // This CPU booted in EL2 > + mov w0, #BOOT_CPU_MODE_EL2 // This CPU booted in EL2 > eret > ENDPROC(el2_setup) > > /* > * Sets the __boot_cpu_mode flag depending on the CPU boot mode passed > - * in x20. See arch/arm64/include/asm/virt.h for more info. > + * in w0. See arch/arm64/include/asm/virt.h for more info. > */ > ENTRY(set_cpu_boot_mode_flag) > adr_l x1, __boot_cpu_mode > - cmp w20, #BOOT_CPU_MODE_EL2 > + cmp w0, #BOOT_CPU_MODE_EL2 > b.ne 1f > add x1, x1, #4 > -1: str w20, [x1] // This CPU has booted in EL1 > +1: str w0, [x1] // This CPU has booted in EL1 > dmb sy > dc ivac, x1 // Invalidate potentially stale cache line > ret > @@ -576,7 +576,7 @@ ENTRY(__boot_cpu_mode) > * cores are held until we're ready for them to initialise. > */ > ENTRY(secondary_holding_pen) > - bl el2_setup // Drop to EL1, w20=cpu_boot_mode > + bl el2_setup // Drop to EL1, w0=cpu_boot_mode > bl set_cpu_boot_mode_flag > mrs x0, mpidr_el1 > ldr x1, =MPIDR_HWID_BITMASK > -- > 2.6.2 >