Re: [PATCH] ARM: rockchip: Convert resume code to C
From: Russell King - ARM Linux
Date: Mon Dec 01 2014 - 17:51:53 EST
On Mon, Dec 01, 2014 at 11:21:34AM -0800, Doug Anderson wrote:
> We convert the existing assembly resume code into C as proof that this
> works and to prepare for linking in SDRAM reinit code.
> base my patch atop them. Why?
That's a very good question...
> +static void __noreturn rk3288_resume_c(void)
> + if (rk3288_resume_params.l2ctlr_f)
> + asm("mcr p15, 1, %0, c9, c0, 2" : :
> + "r" (rk3288_resume_params.l2ctlr));
> +static void __naked __noreturn rk3288_resume(void)
> + /* Make sure we're on CPU0, no IRQs and get a stack setup */
> + asm volatile (
> + "msr cpsr_cxf, %0\n"
> + /* Only cpu0 continues to run, the others halt here */
> + "mrc p15, 0, r1, c0, c0, 5\n"
> + "and r1, r1, #0xf\n"
> + "cmp r1, #0\n"
> + "beq cpu0run\n"
> + "secondary_loop:\n"
> + "wfe\n"
> + "b secondary_loop\n"
> + "cpu0run:\n"
> + "mov sp, %1\n"
> + :
> + : "i" (INIT_CPSR), "r" (&__stack_start)
> + : "cc", "r1", "sp");
Big load of assembly.
What I see here is a load of complexity which achieves very little.
The result doesn't get rid of much assembly, but it does make stuff
more complicated. And the diffstat speaks volumes about this:
10 files changed, 275 insertions(+), 94 deletions(-)
There's a lot of words in the description, but it's missing the most
important bit: why do we want to take this approach - what benefits
does it bring?
FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up
according to speedtest.net.
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