linux-kernel - Re: [PATCH v4 5/5] irqchip, gicv3-its: Workaround for Cavium ThunderX errata 22375, 24313

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Message-ID: <55EDBC19.2010301@arm.com>
Date:	Mon, 07 Sep 2015 17:32:25 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Robert Richter <rric@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>
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 5/5] irqchip, gicv3-its: Workaround for Cavium ThunderX
 errata 22375, 24313

On 14/08/15 19:28, Robert Richter wrote:
> From: Robert Richter <rrichter@...ium.com>
> 
> This implements two gicv3-its errata workarounds for ThunderX. Both
> with small impact affecting only ITS table allocation.
> 
>  erratum 22375: only alloc 8MB table size
>  erratum 24313: ignore memory access type
> 
> The fixes are in ITS initialization and basically ignore memory access
> type and table size provided by the TYPER and BASER registers.
> 
> v3:
>  * fix erratum to be dependend from iidr
> 
> Signed-off-by: Robert Richter <rrichter@...ium.com>
> ---
>  drivers/irqchip/irq-gic-v3-its.c | 35 +++++++++++++++++++++++++++++++----
>  1 file changed, 31 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 697421e834ee..30459df2ee2c 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -39,7 +39,8 @@
>  #include "irq-gic-common.h"
>  #include "irqchip.h"
>  
> -#define ITS_FLAGS_CMDQ_NEEDS_FLUSHING		(1 << 0)
> +#define ITS_FLAGS_CMDQ_NEEDS_FLUSHING		(1ULL << 0)
> +#define ITS_FLAGS_CAVIUM_THUNDERX		(1ULL << 1)

I think you might need something slightly more explicit, as I'd expect
some ulterior revision of ThunderX to be eventually fixed...
ITS_FLAGS_THUNDERX_BOGUS_TYPER? Or something based on the errata numbers?

>  
>  #define RDIST_FLAGS_PROPBASE_NEEDS_FLUSHING	(1 << 0)
>  
> @@ -803,9 +804,22 @@ static int its_alloc_tables(struct its_node *its)
>  	int i;
>  	int psz = SZ_64K;
>  	u64 shr = GITS_BASER_InnerShareable;
> -	u64 cache = GITS_BASER_WaWb;
> -	u64 typer = readq_relaxed(its->base + GITS_TYPER);
> -	u32 ids = GITS_TYPER_DEVBITS(typer);
> +	u64 cache;
> +	u64 typer;
> +	u32 ids;
> +
> +	if (its->flags & ITS_FLAGS_CAVIUM_THUNDERX) {
> +		/*
> +		 * erratum 22375: only alloc 8MB table size
> +		 * erratum 24313: ignore memory access type
> +		 */
> +		cache	= 0;
> +		ids	= 0x13;			/* 20 bits, 8MB */
> +	} else {

You can move the typer definition here, as it is only used here.

> +		cache	= GITS_BASER_WaWb;
> +		typer	= readq_relaxed(its->base + GITS_TYPER);
> +		ids	= GITS_TYPER_DEVBITS(typer);
> +	}
>  
>  	for (i = 0; i < GITS_BASER_NR_REGS; i++) {
>  		u64 val = readq_relaxed(its->base + GITS_BASER + i * 8);
> @@ -1391,8 +1405,21 @@ static int its_force_quiescent(void __iomem *base)
>  	}
>  }
>  
> +static void its_enable_cavium_thunderx(void *data)
> +{
> +	struct its_node *its = data;
> +
> +	its->flags |= ITS_FLAGS_CAVIUM_THUNDERX;
> +}
> +
>  static const struct gic_capabilities its_errata[] = {
>  	{
> +		.desc	= "ITS: Cavium errata 22375, 24313",
> +		.iidr	= 0xa100034c,	/* ThunderX pass 1.x */
> +		.mask	= 0xffff0fff,
> +		.init	= its_enable_cavium_thunderx,
> +	},
> +	{
>  	}
>  };
>  
> 

Otherwise looks OK to me.

Thanks,

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