[U-Boot] sunxi: CPU disabling

[Jan Kiszka <jan.kiszka@web.de>]

On 2014-11-17 07:47, Jan Kiszka wrote:
> On 2014-11-10 14:10, Marc Zyngier wrote:
>> On 10/11/14 12:57, Jan Kiszka wrote:
>>> Hi all,
>>>
>>> I'm trying to get Marc's CPU hotplug-anabling patch [1] for sunxi
>>> working on a B-Pi. After the first discussion it became clear that we
>>> need something like flush_dcache_all in the PSCI monitor (I don't think
>>> we need an icache flush, do we?). Does anyone have a clever suggestion
>>
>> No, I-cache can be left alone.
>>
>>> how to reuse the existing code for that? Or do we really need to
>>> re-implement everything, in the worst case in assembly?
>>
>> Why don't you turn the u-boot code into a set of macros, included by
>> both the core u-boot code and the PSCI code?
> 
> I've now ported over v7_flush_dcache_all from the Linux kernel.
> 
> However, that didn't magically solve the remaining issues with your
> patch: I'm getting crashes on CPU 0 after handling the shoot-down FIQ.
> That is even then the case if I only acknowledge the FIQ on the receiver
> side, don't do any fiddling with CPU1's power states. Only if I
> disabling sending the FIQ from CPU 1, the system remains stable in a CPU
> off/on loop.
> 
> Below the patch I'm using. Any ideas if something is wrong with the FIQ
> handler or the setup of this mechanism or whatever?
> 
> Jan
> 
> ---
> 
> diff --git a/arch/arm/cpu/armv7/sunxi/psci.S b/arch/arm/cpu/armv7/sunxi/psci.S
> index b9ea78b..0e4bca4 100644
> --- a/arch/arm/cpu/armv7/sunxi/psci.S
> +++ b/arch/arm/cpu/armv7/sunxi/psci.S
> @@ -18,6 +18,7 @@
>   */
>  
>  #include <config.h>
> +#include <asm/gic.h>
>  #include <asm/psci.h>
>  #include <asm/arch/cpu.h>
>  
> @@ -38,6 +39,8 @@
>  
>  #define	ONE_MS			(CONFIG_SYS_CLK_FREQ / 1000)
>  #define	TEN_MS			(10 * ONE_MS)
> +#define	GICD_BASE		0x1c81000
> +#define	GICC_BASE		0x1c82000
>  
>  .macro	timer_wait	reg, ticks
>  	@ Program CNTP_TVAL
> @@ -61,7 +64,27 @@
>  
>  .globl	psci_arch_init
>  psci_arch_init:
> +	movw	r4, #(GICD_BASE & 0xffff)
> +	movt	r4, #(GICD_BASE >> 16)
> +
> +	ldr	r5, [r4, #GICD_IGROUPRn]
> +	bic	r5, r5, #(1 << 15) 	@ SGI15 as Group-0
> +	str	r5, [r4, #GICD_IGROUPRn]
> +
> +	mov	r5, #0			@ Set SGI15 priority to 0
> +	strb	r5, [r4, #(GICD_IPRIORITYRn + 15)]
> +
> +	add	r4, r4, #0x1000		@ GICC address
> +
> +	mov	r5, #0xff
> +	str	r5, [r4, #GICC_PMR]	@ Be cool with non-secure
> +
> +	ldr	r5, [r4, #GICC_CTLR]
> +	orr	r5, r5, #(1 << 3)	@ Switch FIQEn on
> +	str	r5, [r4, #GICC_CTLR]
> +
>  	mrc	p15, 0, r5, c1, c1, 0	@ Read SCR
> +	orr	r5, r5, #4		@ Enable FIQ in monitor mode
>  	bic	r5, r5, #1		@ Secure mode
>  	mcr	p15, 0, r5, c1, c1, 0	@ Write SCR
>  	isb
> @@ -79,6 +102,77 @@ psci_arch_init:
>  
>  	bx	lr
>  
> +.globl	psci_fiq_enter
> +psci_fiq_enter:
> +	push	{r0-r12}
> +
> +	@ Switch to secure
> +	mrc	p15, 0, r7, c1, c1, 0
> +	bic	r8, r7, #1
> +	mcr	p15, 0, r8, c1, c1, 0
> +	isb
> +
> +	movw	r8, #(GICC_BASE & 0xffff)
> +	movt	r8, #(GICC_BASE >> 16)
> +	ldr	r9, [r8, #GICC_IAR]
> +	movw	r10, #0x3ff
> +	movt	r10, #0
> +	cmp	r9, r10
> +	beq	out
> +	movw	r10, #0x3fe
> +	cmp	r9, r10
> +	beq	out
> +	str	r9, [r8, #GICC_EOIR]
> +	dsb
> +
> +	@ Compute CPU number
> +	lsr	r9, r9, #10
> +	and	r9, r9, #0xf
> +
> +	movw	r8, #(SUN7I_CPUCFG_BASE & 0xffff)
> +	movt	r8, #(SUN7I_CPUCFG_BASE >> 16)
> +
> +	@ Wait for the core to enter WFI
> +	lsl	r11, r9, #6		@ x64
> +	add	r11, r11, r8
> +
> +1:	ldr	r10, [r11, #0x48]
> +	tst	r10, #(1 << 2)
> +	bne	2f
> +	timer_wait r10, ONE_MS
> +	b	1b
> +
> +	@ Reset CPU
> +2:	mov	r10, #0
> +	str	r10, [r11, #0x40]
> +
> +	@ Lock CPU
> +	mov	r10, #1
> +	lsl	r9, r10, r9		@ r9 is now CPU mask
> +	ldr	r10, [r8, #0x1e4]
> +	bic	r10, r10, r9
> +	str	r10, [r8, #0x1e4]
> +
> +	@ Set power gating
> +	ldr	r10, [r8, #0x1b4]
> +	orr	r10, r10, #1
> +	str	r10, [r8, #0x1b4]
> +	timer_wait r10, ONE_MS
> +
> +	@ Activate power clamp
> +	mov	r10, #1
> +1:	str	r10, [r8, #0x1b0]
> +	lsl	r10, r10, #1
> +	orr	r10, r10, #1
> +	tst	r10, #0x100
> +	beq	1b
> +
> +	@ Restore security level
> +out:	mcr	p15, 0, r7, c1, c1, 0
> +
> +	pop	{r0-r12}
> +	movs	pc, lr

We have to use "subs pc, lr, #4" to return from FIQ. I guess you can
explain better than I why, I only stumbled over this in a stackoverflow
posting - and it works!

Jan


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