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

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Date:	Mon, 07 Sep 2015 17:54:06 +0100
From:	"Suzuki K. Poulose" <Suzuki.Poulose@....com>
To:	Robert Richter <rric@...nel.org>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>
CC:	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>,
	Robert Richter <rrichter@...ium.com>
Subject: Re: [PATCH v4 2/5] irqchip, gicv3: Workaround for Cavium ThunderX
 erratum 23154

On 14/08/15 19:28, Robert Richter wrote:
> From: Robert Richter <rrichter@...ium.com>
>
> This patch implements Cavium ThunderX erratum 23154.
>
> The gicv3 of ThunderX requires a modified version for reading the IAR
> status to ensure data synchronization. Since this is in the fast-path
> and called with each interrupt, runtime patching is used using jump
> label patching for smallest overhead (no-op). This is the same
> technique as used for tracepoints.
>
> v4:
>   * simplify code to only use cpus_have_cap() in gicv3_enable_quirks()
>
> v3:
>   * fix erratum to be dependend from midr
>   * use arm64 errata framework
>
> v2:
>   * implement code in a single asm() to keep instruction sequence
>   * added comment to the code that explains the erratum
>   * apply workaround also if running as guest, thus check MIDR
>
> Signed-off-by: Robert Richter <rrichter@...ium.com>
> ---
>   arch/arm64/Kconfig                  | 11 ++++++++++
>   arch/arm64/include/asm/cpufeature.h |  3 ++-
>   arch/arm64/include/asm/cputype.h    | 18 +++++++++-------
>   arch/arm64/kernel/cpu_errata.c      |  9 ++++++++
>   drivers/irqchip/irq-gic-v3.c        | 42 ++++++++++++++++++++++++++++++++++++-
>   5 files changed, 74 insertions(+), 9 deletions(-)
>

...

>   };
> 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


> +}
> +
>   static int __init gic_of_init(struct device_node *node, struct device_node *parent)
>   {
>   	void __iomem *dist_base;
> @@ -825,6 +863,8 @@ static int __init gic_of_init(struct device_node *node, struct device_node *pare
>   	gic_data.nr_redist_regions = nr_redist_regions;
>   	gic_data.redist_stride = redist_stride;
>
> +	gicv3_enable_quirks();
> +

than adding a hook here ?

Cheers
Suzuki


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