linux-kernel - Re: [PATCH v4 1/3] ARM: rockchip: fix the CPU soft reset

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Date:	Sat, 6 Jun 2015 20:43:04 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	Caesar Wang <wxt@...k-chips.com>
Cc:	Heiko Stuebner <heiko@...ech.de>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	Russell King <linux@....linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 1/3] ARM: rockchip: fix the CPU soft reset

Caesar,

On Sat, Jun 6, 2015 at 7:51 PM, Caesar Wang <wxt@...k-chips.com> wrote:
> @@ -150,13 +159,15 @@ static int __cpuinit rockchip_boot_secondary(unsigned
> int cpu,
>                  * sram_base_addr + 4: 0xdeadbeaf
>                  * sram_base_addr + 8: start address for pc
>                  * */
> -               udelay(10);
> +               udelay(20);
>
> I increased the 'udelay(20)' or 'udelay(50)' in rockchip_boot_secondary().
> Set#2 also can repro this issue over 22600 cycles with testing scripts.
> (about 1 hours)
>
> log:
> ================= 226 ============
> [ 4069.134419] CPU1: shutdown
> [ 4069.164431] CPU2: shutdown
> [ 4069.204475] CPU3: shutdown
> ......
> [ 4072.454453] CPU1: shutdown
> [ 4072.504436] CPU2: shutdown
> [ 4072.554426] CPU3: shutdown
> [ 4072.577827] CPU1: Booted secondary processor
> [ 4072.582611] CPU2: Booted secondary processor
> [ 4072.587426] CPU3: Booted secondary processor
> <hang>
>
> The set #4 will be better work.

OK, I'm OK with this, but I'd like to get Heiko's opinion.

Also:
* Just for kicks, does mdelay(1) work?  I know that's 100x more than
udelay(10), but previously we were actually looping waiting for the
power domain, right?  ...so maybe the old code used to introduce a
pretty big delay.

* Does anyone from the chip design team have any idea why patch set #4
works but patch set #2 doesn't?  I know it's Sunday morning in China
right now, but maybe you could ask Monday?


Thanks!

-Doug
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