Messages in this thread | | | Subject | 答复: [PATCH v4 20/28] ARM: owl: I mplement CPU enable-method for S 500 | Date | Sat, 1 Jul 2017 12:42:56 +0800 | From | 刘炜 <> |
| |
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
-- SUSE Linux GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Felix Imendörffer, Jane Smithard, Graham Norton HRB 21284 (AG Nürnberg)
| |