linux-kernel - Re: [PATCH v2 6/8] bus: brcmstb

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Message-ID: <20170329112030.GD23442@leverpostej>
Date:   Wed, 29 Mar 2017 12:20:31 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Doug Berger <opendmb@...il.com>
Cc:     robh+dt@...nel.org, catalin.marinas@....com, will.deacon@....com,
        computersforpeace@...il.com, gregory.0xf0@...il.com,
        f.fainelli@...il.com, bcm-kernel-feedback-list@...adcom.com,
        wangkefeng.wang@...wei.com, james.morse@....com, mingo@...nel.org,
        sandeepa.s.prabhu@...il.com, shijie.huang@....com,
        linus.walleij@...aro.org, treding@...dia.com, jonathanh@...dia.com,
        olof@...om.net, mirza.krak@...il.com, suzuki.poulose@....com,
        bgolaszewski@...libre.com, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 6/8] bus: brcmstb_gisb: Add ARM64 support

Hi,

On Tue, Mar 28, 2017 at 02:34:29PM -0700, Doug Berger wrote:
> From: Florian Fainelli <f.fainelli@...il.com>
> 
> Hook to the ARM64 data abort exception #16: synchronous external
> abort, which is how the GISB errors will be funneled back to the
> ARM64 CPU in case of problems

I believe that you can use a die notifier for this, and that you don't
need to hook the low-level architectural fault here.

I note that the code doesn't even look at the faulting address, and
likely doesn't have the information to do anything with it, so it make
no sense to me for this code to hook the low-level fault.

Further, as an aside, from digging into how we handle unexpected faults
it appears that we don't always treat some faults (e.g. TLB conflict,
faults on PTW) sufficiently fatally when they occur at EL0, so we likely
need to do so rework there.

Thanks,
Mark.

> 
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>  drivers/bus/Kconfig        |  2 +-
>  drivers/bus/brcmstb_gisb.c | 15 ++++++++++++---
>  2 files changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
> index 0a52da439abf..d2a5f1184022 100644
> --- a/drivers/bus/Kconfig
> +++ b/drivers/bus/Kconfig
> @@ -57,7 +57,7 @@ config ARM_CCN
>  
>  config BRCMSTB_GISB_ARB
>  	bool "Broadcom STB GISB bus arbiter"
> -	depends on ARM || MIPS
> +	depends on ARM || ARM64 || MIPS
>  	default ARCH_BRCMSTB || BMIPS_GENERIC
>  	help
>  	  Driver for the Broadcom Set Top Box System-on-a-chip internal bus
> diff --git a/drivers/bus/brcmstb_gisb.c b/drivers/bus/brcmstb_gisb.c
> index edf79432f899..500b6bb5c739 100644
> --- a/drivers/bus/brcmstb_gisb.c
> +++ b/drivers/bus/brcmstb_gisb.c
> @@ -30,6 +30,11 @@
>  #include <asm/signal.h>
>  #endif
>  
> +#ifdef CONFIG_ARM64
> +#include <asm/signal.h>
> +#include <asm/system_misc.h>
> +#endif
> +
>  #ifdef CONFIG_MIPS
>  #include <asm/traps.h>
>  #endif
> @@ -225,7 +230,7 @@ static int brcmstb_gisb_arb_decode_addr(struct brcmstb_gisb_arb_device *gdev,
>  	return 0;
>  }
>  
> -#ifdef CONFIG_ARM
> +#if defined(CONFIG_ARM) || defined(CONFIG_ARM64)
>  static int brcmstb_bus_error_handler(unsigned long addr, unsigned int fsr,
>  				     struct pt_regs *regs)
>  {
> @@ -235,7 +240,7 @@ static int brcmstb_bus_error_handler(unsigned long addr, unsigned int fsr,
>  	list_for_each_entry(gdev, &brcmstb_gisb_arb_device_list, next)
>  		brcmstb_gisb_arb_decode_addr(gdev, "bus error");
>  
> -#if !defined(CONFIG_ARM_LPAE)
> +#if defined(CONFIG_ARM) && !defined(CONFIG_ARM_LPAE)
>  	/*
>  	 * If it was an imprecise abort, then we need to correct the
>  	 * return address to be _after_ the instruction.
> @@ -247,7 +252,7 @@ static int brcmstb_bus_error_handler(unsigned long addr, unsigned int fsr,
>  	/* Always report unhandled exception */
>  	return 1;
>  }
> -#endif
> +#endif /* CONFIG_ARM || CONFIG_ARM64 */
>  
>  #ifdef CONFIG_MIPS
>  static int brcmstb_bus_error_handler(struct pt_regs *regs, int is_fixup)
> @@ -395,6 +400,10 @@ static int __init brcmstb_gisb_arb_probe(struct platform_device *pdev)
>  			"imprecise external abort");
>  #endif
>  #endif /* CONFIG_ARM */
> +#ifdef CONFIG_ARM64
> +	hook_fault_code(16, brcmstb_bus_error_handler, SIGBUS, 0,
> +			"synchronous external abort");
> +#endif
>  #ifdef CONFIG_MIPS
>  	board_be_handler = brcmstb_bus_error_handler;
>  #endif
> -- 
> 2.12.0
>