linux-kernel - Re: [PATCH v4 4/4] x86/of: Add support for boot time interrupt delivery mode configuration

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Date:   Wed, 23 Nov 2022 15:44:48 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Rahul Tanwar <rtanwar@...linear.com>
Cc:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-lgm-soc@...linear.com
Subject: Re: [PATCH v4 4/4] x86/of: Add support for boot time interrupt
 delivery mode configuration

On Wed, Nov 23, 2022 at 06:08:50PM +0800, Rahul Tanwar wrote:
> Presently, init/boot time interrupt delivery mode is enumerated
> only for ACPI enabled systems by parsing MADT table or for older
> systems by parsing MP table. But for OF based x86 systems, it is
> assumed & hardcoded to legacy PIC mode. This causes boot time crash
> for platforms which do not use 8259 compliant legacy PIC.
> 
> Add support for configuration of init time interrupt delivery mode
> for x86 OF based systems by introducing a new optional boolean
> property 'intel,virtual-wire-mode' for interrupt-controller node
> of local APIC. This property emulates IMCRP Bit 7 of MP feature
> info byte 2 of MP floating pointer structure.
> 
> Defaults to legacy PIC mode if absent. Configures it to virtual
> wire compatibility mode if present.

>From code perspective looks good to me, but you need to have a blessing by DT
people for first two patches.

With whatever property name agreed on,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

> Signed-off-by: Rahul Tanwar <rtanwar@...linear.com>
> ---
>  arch/x86/kernel/devicetree.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/devicetree.c b/arch/x86/kernel/devicetree.c
> index fcc6f1b7818f..458e43490414 100644
> --- a/arch/x86/kernel/devicetree.c
> +++ b/arch/x86/kernel/devicetree.c
> @@ -167,7 +167,14 @@ static void __init dtb_lapic_setup(void)
>  			return;
>  	}
>  	smp_found_config = 1;
> -	pic_mode = 1;
> +	if (of_property_read_bool(dn, "intel,virtual-wire-mode")) {
> +		pr_info("Virtual Wire compatibility mode.\n");
> +		pic_mode = 0;
> +	} else {
> +		pr_info("IMCR and PIC compatibility mode.\n");
> +		pic_mode = 1;
> +	}
> +
>  	register_lapic_address(lapic_addr);
>  }
>  
> -- 
> 2.17.1
> 

-- 
With Best Regards,
Andy Shevchenko