From: Neil Armstrong <narmstrong@baylibre.com>
To: Arnd Bergmann <arnd@arndb.de>, linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org, linux-oxnas@lists.tuxfamily.org
Subject: Re: [PATCH 1/2] ARM: oxnas: Add OX820 SMP support
Date: Mon, 17 Oct 2016 11:34:32 +0200 [thread overview]
Message-ID: <9124cda0-d16b-0992-2552-8a617aeb5d40@baylibre.com> (raw)
In-Reply-To: <14513531.isB50DxNJf@wuerfel>
On 10/17/2016 11:06 AM, Arnd Bergmann wrote:
> On Monday, October 17, 2016 10:43:02 AM CEST Neil Armstrong wrote:
>> +
>> + /*
>> + * This is really belt and braces; we hold unintended secondary
>> + * CPUs in the holding pen until we're ready for them. However,
>> + * since we haven't sent them a soft interrupt, they shouldn't
>> + * be there.
>> + */
>> + write_pen_release(cpu);
>> +
>> + /*
>> + * Enable GIC cpu interface in CPU Interface Control Register
>> + */
>> + writel(GIC_CPU_CTRL_ENABLE,
>> + gic_cpu_ctrl + GIC_NCPU_OFFSET(cpu) + GIC_CPU_CTRL);
>> +
>> + /*
>> + * Send the secondary CPU a soft interrupt, thereby causing
>> + * the boot monitor to read the system wide flags register,
>> + * and branch to the address found there.
>> + */
>> +
>> + arch_send_wakeup_ipi_mask(cpumask_of(cpu));
>> + timeout = jiffies + (1 * HZ);
>> + while (time_before(jiffies, timeout)) {
>> + smp_rmb();
>> + if (read_pen_release() == -1)
>> + break;
>> +
>> + udelay(10);
>> + }
>>
>
> This seems to have been copied from plat-versatile, but is really
> not needed here since you apparently have proper hardware support for
> starting up the CPUs.
Yes it seems.
>
> Any reason you can't just write to the cpu_ctrl register
> once and keep going without that whole holding_pen loop
> and spinlock?
I suppose but I did not find any good examples except the plat-versatile code.
I will try some simpler code.
>
> Arnd
>
Neil
WARNING: multiple messages have this Message-ID (diff)
From: narmstrong@baylibre.com (Neil Armstrong)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/2] ARM: oxnas: Add OX820 SMP support
Date: Mon, 17 Oct 2016 11:34:32 +0200 [thread overview]
Message-ID: <9124cda0-d16b-0992-2552-8a617aeb5d40@baylibre.com> (raw)
In-Reply-To: <14513531.isB50DxNJf@wuerfel>
On 10/17/2016 11:06 AM, Arnd Bergmann wrote:
> On Monday, October 17, 2016 10:43:02 AM CEST Neil Armstrong wrote:
>> +
>> + /*
>> + * This is really belt and braces; we hold unintended secondary
>> + * CPUs in the holding pen until we're ready for them. However,
>> + * since we haven't sent them a soft interrupt, they shouldn't
>> + * be there.
>> + */
>> + write_pen_release(cpu);
>> +
>> + /*
>> + * Enable GIC cpu interface in CPU Interface Control Register
>> + */
>> + writel(GIC_CPU_CTRL_ENABLE,
>> + gic_cpu_ctrl + GIC_NCPU_OFFSET(cpu) + GIC_CPU_CTRL);
>> +
>> + /*
>> + * Send the secondary CPU a soft interrupt, thereby causing
>> + * the boot monitor to read the system wide flags register,
>> + * and branch to the address found there.
>> + */
>> +
>> + arch_send_wakeup_ipi_mask(cpumask_of(cpu));
>> + timeout = jiffies + (1 * HZ);
>> + while (time_before(jiffies, timeout)) {
>> + smp_rmb();
>> + if (read_pen_release() == -1)
>> + break;
>> +
>> + udelay(10);
>> + }
>>
>
> This seems to have been copied from plat-versatile, but is really
> not needed here since you apparently have proper hardware support for
> starting up the CPUs.
Yes it seems.
>
> Any reason you can't just write to the cpu_ctrl register
> once and keep going without that whole holding_pen loop
> and spinlock?
I suppose but I did not find any good examples except the plat-versatile code.
I will try some simpler code.
>
> Arnd
>
Neil
next prev parent reply other threads:[~2016-10-17 9:34 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-17 8:43 [PATCH 0/2] ARM: oxnas: Add SMP support for OX820 Neil Armstrong
2016-10-17 8:43 ` Neil Armstrong
2016-10-17 8:43 ` [PATCH 1/2] ARM: oxnas: Add OX820 SMP support Neil Armstrong
2016-10-17 8:43 ` Neil Armstrong
2016-10-17 9:06 ` Arnd Bergmann
2016-10-17 9:06 ` Arnd Bergmann
2016-10-17 9:34 ` Neil Armstrong [this message]
2016-10-17 9:34 ` Neil Armstrong
2016-10-31 8:18 ` Russell King - ARM Linux
2016-10-31 8:18 ` Russell King - ARM Linux
2016-10-17 8:43 ` [PATCH 2/2] ARM: oxnas: Add OX820 config and makefile entry Neil Armstrong
2016-10-17 8:43 ` Neil Armstrong
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