linux-kernel - Re: [PATCH] MIPS: mips-cm: CM regions are disabled at boot

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Date:	Thu, 20 Nov 2014 12:34:34 +0000
From:	Paul Burton <paul.burton@...tec.com>
To:	Niklas Svensson <niklas.svensson@...s.com>
CC:	<ralf@...ux-mips.org>, <linux-mips@...ux-mips.org>,
	<linux-kernel@...r.kernel.org>, Niklas Svensson <niklass@...s.com>
Subject: Re: [PATCH] MIPS: mips-cm: CM regions are disabled at boot

On Thu, Nov 20, 2014 at 01:29:00PM +0100, Niklas Svensson wrote:
> Each CM_REGION_TARGET is set to disabled at boot,

That part is true...

> so there is no need to disable the matching
> CM_GCR_REG explicitly.

...however there is no guarantee that the bootloader, or another kernel,
or some other piece of code didn't program the registers differently
before Linux starts. So I believe this patch to be incorrect.

Thanks,
    Paul

> 
> Signed-off-by: Niklas Svensson <niklass@...s.com>
> ---
>  arch/mips/kernel/mips-cm.c | 10 ----------
>  1 file changed, 10 deletions(-)
> 
> diff --git a/arch/mips/kernel/mips-cm.c b/arch/mips/kernel/mips-cm.c
> index f76f7a0..a4bbfd9 100644
> --- a/arch/mips/kernel/mips-cm.c
> +++ b/arch/mips/kernel/mips-cm.c
> @@ -104,16 +104,6 @@ int mips_cm_probe(void)
>  	base_reg |= CM_GCR_BASE_CMDEFTGT_MEM;
>  	write_gcr_base(base_reg);
>  
> -	/* disable CM regions */
> -	write_gcr_reg0_base(CM_GCR_REGn_BASE_BASEADDR_MSK);
> -	write_gcr_reg0_mask(CM_GCR_REGn_MASK_ADDRMASK_MSK);
> -	write_gcr_reg1_base(CM_GCR_REGn_BASE_BASEADDR_MSK);
> -	write_gcr_reg1_mask(CM_GCR_REGn_MASK_ADDRMASK_MSK);
> -	write_gcr_reg2_base(CM_GCR_REGn_BASE_BASEADDR_MSK);
> -	write_gcr_reg2_mask(CM_GCR_REGn_MASK_ADDRMASK_MSK);
> -	write_gcr_reg3_base(CM_GCR_REGn_BASE_BASEADDR_MSK);
> -	write_gcr_reg3_mask(CM_GCR_REGn_MASK_ADDRMASK_MSK);
> -
>  	/* probe for an L2-only sync region */
>  	mips_cm_probe_l2sync();
>  
> -- 
> 2.1.3
> 
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