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Subject答复: [PATCH v4 20/28] ARM: owl: I mplement CPU enable-method for S 500
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Hi, Andrea

OWL_CPUx_ADDR is the physical address of CPUx wakeup function.
OWL_CPUx_FLAG is a valid flag of OWL_CPUx_ADDR.

After CPUxs are wakeuped by SEV instruction, they will check their own OWL_CPUx_FLAG register. If the register vlaue is 0x55aa, CPUx will jump to OWL_CPUx_ADDR to boot up, otherwize go to sleep by WFE.

So the pen release staff is not necessary, you can remove these code safely.

BTW: CPU2/3 must exit the power gate state before wakeup, and CPU1 is always power on and has no power gate control.

Best Regards,
David Liu

-----邮件原件-----
发件人: Andreas Färber [mailto:afaerber@suse.de]
发送时间: 2017年6月29日 23:22
收件人: Arnd Bergmann; Thomas Liau
抄送: Linux ARM; mp-cs; 张东风; 刘炜; 张天益; 96boards@ucrobotics.com; support@lemaker.org; Linux Kernel Mailing List; Russell King
主题: Re: [PATCH v4 20/28] ARM: owl: Implement CPU enable-method for S500

Am 29.06.2017 um 17:07 schrieb Arnd Bergmann:
>>> +static int s500_smp_boot_secondary(unsigned int cpu, struct
>>> +task_struct *idle) {
>>> + unsigned long timeout;
>>> + int ret;
>>> +
>>> + ret = s500_wakeup_secondary(cpu);
>>> + if (ret)
>>> + return ret;
>>> +
>>> + udelay(10);
>>> +
>>> + spin_lock(&boot_lock);
>>> +
>>> + /*
>>> + * The secondary processor is waiting to be released from
>>> + * the holding pen - release it, then wait for it to flag
>>> + * that it has been released by resetting pen_release.
>>> + */
>>> + write_pen_release(cpu_logical_map(cpu));
>>> + smp_send_reschedule(cpu);
>>> +
>>> + timeout = jiffies + (1 * HZ);
>>> + while (time_before(jiffies, timeout)) {
>>> + if (pen_release == -1)
>>> + break;
>>> + }
>>> +
>>> + writel(0, timer_base_addr + OWL_CPU1_ADDR + (cpu - 1) * 4);
>>> + writel(0, timer_base_addr + OWL_CPU1_FLAG + (cpu - 1) * 4);
>>> +
>>> + spin_unlock(&boot_lock);
>>> +
>>> + return pen_release != -1 ? -ENOSYS : 0; }
>>
>> This looks more complicated than necessary. Why do you need the
>> holding pen when you have a register to start up the CPU?
>>
>
> It seems you missed my question here. Can you please follow up, and if
> possible send a patch to remove the pen_release logic that appears to
> be unnecessary here?

I do not have any documentation on these registers, only the downstream code that I forward-ported here. If you tell me what you mean exactly, I can do some testing and if it still works submit a patch to simplify it.

Comments from the so far quiet Actions Semi side would help, too.

Regards,
Andreas

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SUSE Linux GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Felix Imendörffer, Jane Smithard, Graham Norton HRB 21284 (AG Nürnberg)
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