linux-kernel - Re: [PATCH v4 2/5] irqchip, gicv3: Workaround for Cavium ThunderX erratum 23154

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Date:	Mon, 7 Sep 2015 18:15:01 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	"Suzuki K. Poulose" <Suzuki.Poulose@....com>
Cc:	Robert Richter <rric@...nel.org>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Will Deacon <Will.Deacon@....com>,
	Robert Richter <rrichter@...ium.com>,
	Tirumalesh Chalamarla <tchalamarla@...ium.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 2/5] irqchip, gicv3: Workaround for Cavium ThunderX
 erratum 23154

On Mon, Sep 07, 2015 at 05:54:06PM +0100, Suzuki K. Poulose wrote:
> On 14/08/15 19:28, Robert Richter wrote:
> >diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> >index c52f7ba205b4..4211c39b8744 100644
> >--- a/drivers/irqchip/irq-gic-v3.c
> >+++ b/drivers/irqchip/irq-gic-v3.c
> >@@ -107,7 +107,7 @@ static void gic_redist_wait_for_rwp(void)
> 
> ...
> 
> >+}
> >+
> >  static void __maybe_unused gic_write_pmr(u64 val)
> >  {
> >  	asm volatile("msr_s " __stringify(ICC_PMR_EL1) ", %0" : : "r" (val));
> >@@ -766,6 +798,12 @@ static const struct irq_domain_ops gic_irq_domain_ops = {
> >  	.free = gic_irq_domain_free,
> >  };
> >
> >+static void gicv3_enable_quirks(void)
> >+{
> >+	if (cpus_have_cap(ARM64_WORKAROUND_CAVIUM_23154))
> >+		static_key_slow_inc(&is_cavium_thunderx);
> 
> May be you could use the enable() method added to struct arm64_cpu_capability
> here to perform the above operation, added by James :
> 
> commit 1c0763037f1e1caef739e36e09c6d41ed7b61b2d
> Author: James Morse <james.morse@....com>
> Date:   Tue Jul 21 13:23:28 2015 +0100
> 
>     arm64: kernel: Add cpufeature 'enable' callback

I thought about this as well when looking at the patch but decided it's
better as it is. The "enable" method is meant to enable per-CPU features
(or workarounds) but here it is about GICv3, so we don't want to enable
for every CPU.

-- 
Catalin
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