linux-kernel - Re: [PATCH v2] irqchip/gic-v3-its: Add workaround for ThunderX2 erratum #174

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Message-ID: <7752cf1b-b929-738b-9e3c-fe379a8c251b@arm.com>
Date:   Fri, 19 Jan 2018 12:23:11 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Ganapatrao Kulkarni <ganapatrao.kulkarni@...ium.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Cc:     tglx@...utronix.de, jason@...edaemon.net, catalin.marinas@....com,
        will.deacon@....com, corbet@....net, jnair@...iumnetworks.com,
        Robert.Richter@...ium.com, Jan.Glauber@...ium.com,
        Vadim.Lomovtsev@...ium.com, gklkml16@...il.com
Subject: Re: [PATCH v2] irqchip/gic-v3-its: Add workaround for ThunderX2
 erratum #174

On 18/01/18 05:28, Ganapatrao Kulkarni wrote:
> This erratum is observed on the ThunderX2 GICv3 ITS. When a
> MOVI command is used to change affinity of a LPI to a collection/cpu
> on another node, the LPI is not delivered to the cpu.
> An additional INV command is required after the MOVI to deliver
> the LPI to the new destination.
> 
> If we add INV after MOVI, there is a chance that we lose LPIs which
> are raised when the affinity is changed. So for now, adding workaround fix
> to disable inter node affinity change.
> 
> Signed-off-by: Ganapatrao Kulkarni <ganapatrao.kulkarni@...ium.com>
> ---
> 
> v2: Added workaround to avoid inter node affinity change.
> 
> v1: Initial patch
> 
>  Documentation/arm64/silicon-errata.txt |  1 +
>  arch/arm64/Kconfig                     | 10 ++++++++++
>  drivers/irqchip/irq-gic-v3-its.c       | 21 ++++++++++++++++++++-
>  3 files changed, 31 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/arm64/silicon-errata.txt b/Documentation/arm64/silicon-errata.txt
> index fc1c884..fb27cb5 100644
> --- a/Documentation/arm64/silicon-errata.txt
> +++ b/Documentation/arm64/silicon-errata.txt
> @@ -63,6 +63,7 @@ stable kernels.
>  | Cavium         | ThunderX Core   | #27456          | CAVIUM_ERRATUM_27456        |
>  | Cavium         | ThunderX Core   | #30115          | CAVIUM_ERRATUM_30115        |
>  | Cavium         | ThunderX SMMUv2 | #27704          | N/A                         |
> +| Cavium         | ThunderX2 ITS   | #174            | CAVIUM_ERRATUM_174          |
>  | Cavium         | ThunderX2 SMMUv3| #74             | N/A                         |
>  | Cavium         | ThunderX2 SMMUv3| #126            | N/A                         |
>  |                |                 |                 |                             |
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index c9a7e9e..0dbf3bd 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -461,6 +461,16 @@ config ARM64_ERRATUM_843419
>  
>  	  If unsure, say Y.
>  
> +config CAVIUM_ERRATUM_174
> +	bool "Cavium ThunderX2 erratum 174"
> +	default y
> +	help
> +	  Cavium ThunderX2 dual socket systems may loose interrupts
> +	  on affinity change to a cpu on other node.
> +	  This workaround fix avoids inter node affinity change.
> +
> +	  If unsure, say Y.
> +
>  config CAVIUM_ERRATUM_22375
>  	bool "Cavium erratum 22375, 24313"
>  	default y
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 06f025f..b0cb528 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -46,6 +46,7 @@
>  #define ITS_FLAGS_CMDQ_NEEDS_FLUSHING		(1ULL << 0)
>  #define ITS_FLAGS_WORKAROUND_CAVIUM_22375	(1ULL << 1)
>  #define ITS_FLAGS_WORKAROUND_CAVIUM_23144	(1ULL << 2)
> +#define ITS_FLAGS_WORKAROUND_CAVIUM_174		(1ULL << 3)

Instead of inventing a new flag, please rename the existing one to
ITS_FLAG_WORKAROUND_RESTRICT_NODE_AFFINITY (or something similar). There
is really no need to have two flags that do the exact same thing,

>  
>  #define RDIST_FLAGS_PROPBASE_NEEDS_FLUSHING	(1 << 0)
>  
> @@ -1102,7 +1103,8 @@ static int its_set_affinity(struct irq_data *d, const struct cpumask *mask_val,
>  		return -EINVAL;
>  
>         /* lpi cannot be routed to a redistributor that is on a foreign node */
> -	if (its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_23144) {
> +	if (its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_23144 ||
> +			its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_174) {
>  		if (its_dev->its->numa_node >= 0) {
>  			cpu_mask = cpumask_of_node(its_dev->its->numa_node);
>  			if (!cpumask_intersects(mask_val, cpu_mask))
> @@ -2904,6 +2906,15 @@ static int its_force_quiescent(void __iomem *base)
>  	}
>  }
>  
> +static bool __maybe_unused its_enable_quirk_cavium_174(void *data)
> +{
> +	struct its_node *its = data;
> +
> +	its->flags |= ITS_FLAGS_WORKAROUND_CAVIUM_174;
> +
> +	return true;
> +}
> +
>  static bool __maybe_unused its_enable_quirk_cavium_22375(void *data)
>  {
>  	struct its_node *its = data;
> @@ -3031,6 +3042,14 @@ static const struct gic_quirk its_quirks[] = {
>  		.init	= its_enable_quirk_hip07_161600802,
>  	},
>  #endif
> +#ifdef CONFIG_CAVIUM_ERRATUM_174
> +	{
> +		.desc	= "ITS: Cavium ThunderX2 erratum 174",
> +		.iidr	= 0x13f,	/* ThunderX2 pass A1/A2/B0 */
> +		.mask	= 0xffffffff,
> +		.init	= its_enable_quirk_cavium_174,
> +	},
> +#endif
>  	{
>  	}
>  };
> 

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...