[PATCH RFC v3 04/12] arm64: kernel: cpu_{suspend/resume} implementation

[Lorenzo Pieralisi]

On Fri, Dec 20, 2013 at 11:30:16AM +0000, Leo Yan wrote:
> On 11/21/2013 07:24 PM, Lorenzo Pieralisi wrote:
> 
> > +/*
> > + * x0 must contain the sctlr value retrieved from restored context
> > + */
> > +ENTRY(cpu_resume_mmu)
> > +	ldr	x3, =cpu_resume_after_mmu
> > +	msr	sctlr_el1, x0		// restore sctlr_el1
> > +	isb
> > +	br	x3			// global jump to virtual address
> > +ENDPROC(cpu_resume_mmu)
> > +cpu_resume_after_mmu:
> > +	mov	x0, #0			// return zero on success
> > +	ldp	x19, x20, [sp, #16]
> > +	ldp	x21, x22, [sp, #32]
> > +	ldp	x23, x24, [sp, #48]
> > +	ldp	x25, x26, [sp, #64]
> > +	ldp	x27, x28, [sp, #80]
> > +	ldp	x29, lr, [sp], #96
> > +	ret
> > +ENDPROC(cpu_resume_after_mmu)
> > +
> > +	.data
> > +ENTRY(cpu_resume)
> > +	bl	el2_setup		// if in EL2 drop to EL1 cleanly
> 
> Compare to v2's patch set, here remove the calculation fro the offset 
> b/t PHYS_OFFSET - PAGE_OFFSET; so when i verify the patch set, i saw x28 
> is zero and finally introduce the EL2's sync exception. Below are pasted 
> v2's code for reference.

What kernel are you testing against ? The offset is not needed anymore
in el2_setup, that is why the x28 computation is not there.

> do u want use firmware to set the x28 for the offset value? :-) IMHO, 
> v2's implementation is more reasonable and it's better keep the code.

The point is not whether to set it in firmware or in the kernel, see above.

Lorenzo

> 
> ENTRY(cpu_resume)
>            adr     x4, sleep_save_sp
>            ldr     x5, =sleep_save_sp
>            sub     x28, x4, x5             // x28 = PHYS_OFFSET - 
> PAGE_OFFSET
>            /*
>             * make sure el2 is sane, el2_setup expects:
>             * x28 = PHYS_OFFSET - PAGE_OFFSET
>             */
>            bl      el2_setup               // if in EL2 drop to EL1 cleanly
> 
> 
> > +#ifdef CONFIG_SMP
> > +	mrs	x1, mpidr_el1
> > +	adr	x4, mpidr_hash_ptr
> > +	ldr	x5, [x4]
> > +	add	x8, x4, x5		// x8 = struct mpidr_hash phys address
> > +        /* retrieve mpidr_hash members to compute the hash */
> > +	ldr	x2, [x8, #MPIDR_HASH_MASK]
> > +	ldp	w3, w4, [x8, #MPIDR_HASH_SHIFTS]
> > +	ldp	w5, w6, [x8, #(MPIDR_HASH_SHIFTS + 8)]
> > +	compute_mpidr_hash x7, x3, x4, x5, x6, x1, x2
> > +        /* x7 contains hash index, let's use it to grab context pointer */
> > +#else
> > +	mov	x7, xzr
> > +#endif
> > +	adr	x0, sleep_save_sp
> > +	ldr	x0, [x0, #SLEEP_SAVE_SP_PHYS]
> > +	ldr	x0, [x0, x7, lsl #3]
> > +	/* load sp from context */
> > +	ldr	x2, [x0, #CPU_CTX_SP]
> > +	adr	x1, sleep_idmap_phys
> > +	/* load physical address of identity map page table in x1 */
> > +	ldr	x1, [x1]
> > +	mov	sp, x2
> > +	/*
> > +	 * cpu_do_resume expects x0 to contain context physical address
> > +	 * pointer and x1 to contain physical address of 1:1 page tables
> > +	 */
> > +	bl	cpu_do_resume		// PC relative jump, MMU off
> > +	b	cpu_resume_mmu		// Resume MMU, never returns
> > +ENDPROC(cpu_resume)
> > +
>