linux-kernel - Re: [PATCH] reboot: perform warm/cold reset correctly for CF9 type

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Date:	Wed, 21 Aug 2013 09:29:40 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Li Fei <fei.li@...el.com>
Cc:	hpa@...or.com, mingo@...hat.com, tglx@...utronix.de,
	chuansheng.liu@...el.com, x86@...nel.org,
	akpm@...ux-foundation.org, holt@....com,
	rmk+kernel@....linux.org.uk, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] reboot: perform warm/cold reset correctly for CF9 type


* Li Fei <fei.li@...el.com> wrote:

> In current implementation for reboot type CF9 and CF9_COND,
> warm and cold reset are not differentiated, and both are
> performed by writing 0x06 to port 0xCF9 as warm reset. It's not
> correct.
> 
> This commit will differentiate warm and cold reset, and perform
> them correctly as below:
> For warm reset, write 0x06 to port 0xCF9;
> For cold reset, write 0x0E to port 0xCF9.
> 
> From: Liu Chuansheng <chuansheng.liu@...el.com>
> Signed-off-by: Li Fei <fei.li@...el.com>
> ---
>  arch/x86/kernel/reboot.c |    9 +++++++--
>  1 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
> index 563ed91..6e06299 100644
> --- a/arch/x86/kernel/reboot.c
> +++ b/arch/x86/kernel/reboot.c
> @@ -511,10 +511,15 @@ static void native_machine_emergency_restart(void)
>  
>  		case BOOT_CF9_COND:
>  			if (port_cf9_safe) {
> -				u8 cf9 = inb(0xcf9) & ~6;
> +				u8 cf9 = inb(0xcf9) &
> +						~(reboot_mode == REBOOT_WARM ?
> +						0x06 : 0x0E);
>  				outb(cf9|2, 0xcf9); /* Request hard reset */
>  				udelay(50);
> -				outb(cf9|6, 0xcf9); /* Actually do the reset */
> +				/* Actually do the reset */
> +				outb(cf9|(reboot_mode == REBOOT_WARM ?
> +					0x06 : 0x0E),
> +					0xcf9);
>  				udelay(50);

Looks good, but please introduce a reboot_val intermediate 
variable instead of duplicating that ugly line-broken 
construct twice.

Thanks,

	Ingo
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