linux-kernel - Re: [PATCH 1/2] MIPS: Watch: Avoid duplication of bits in mips_install_watch

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Date:   Fri, 5 Jan 2018 10:11:24 -0800
From:   David Daney <ddaney@...iumnetworks.com>
To:     Matt Redfearn <matt.redfearn@...s.com>, ralf@...ux-mips.org
Cc:     linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] MIPS: Watch: Avoid duplication of bits in
 mips_install_watch_registers.

On 01/02/2018 03:31 AM, Matt Redfearn wrote:
> Currently the bits to be set in the watchhi register in addition to that
> requested by the user is defined inline for each register. To avoid
> this, define the bits once and or that in for each register.
> 
> Signed-off-by: Matt Redfearn <matt.redfearn@...s.com>

Looks like a good cleanup/simplification...

Acked-by: David Daney <david.daney@...ium.com>

> ---
> 
>   arch/mips/kernel/watch.c | 17 +++++++----------
>   1 file changed, 7 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/mips/kernel/watch.c b/arch/mips/kernel/watch.c
> index 19fcab7348b1..329d2209521d 100644
> --- a/arch/mips/kernel/watch.c
> +++ b/arch/mips/kernel/watch.c
> @@ -18,27 +18,24 @@
>   void mips_install_watch_registers(struct task_struct *t)
>   {
>   	struct mips3264_watch_reg_state *watches = &t->thread.watch.mips3264;
> +	unsigned int watchhi = MIPS_WATCHHI_G |		/* Trap all ASIDs */
> +			       MIPS_WATCHHI_IRW;	/* Clear result bits */
> +
>   	switch (current_cpu_data.watch_reg_use_cnt) {
>   	default:
>   		BUG();
>   	case 4:
>   		write_c0_watchlo3(watches->watchlo[3]);
> -		/* Write 1 to the I, R, and W bits to clear them, and
> -		   1 to G so all ASIDs are trapped. */
> -		write_c0_watchhi3(MIPS_WATCHHI_G | MIPS_WATCHHI_IRW |
> -				  watches->watchhi[3]);
> +		write_c0_watchhi3(watchhi | watches->watchhi[3]);
>   	case 3:
>   		write_c0_watchlo2(watches->watchlo[2]);
> -		write_c0_watchhi2(MIPS_WATCHHI_G | MIPS_WATCHHI_IRW |
> -				  watches->watchhi[2]);
> +		write_c0_watchhi2(watchhi | watches->watchhi[2]);
>   	case 2:
>   		write_c0_watchlo1(watches->watchlo[1]);
> -		write_c0_watchhi1(MIPS_WATCHHI_G | MIPS_WATCHHI_IRW |
> -				  watches->watchhi[1]);
> +		write_c0_watchhi1(watchhi | watches->watchhi[1]);
>   	case 1:
>   		write_c0_watchlo0(watches->watchlo[0]);
> -		write_c0_watchhi0(MIPS_WATCHHI_G | MIPS_WATCHHI_IRW |
> -				  watches->watchhi[0]);
> +		write_c0_watchhi0(watchhi | watches->watchhi[0]);
>   	}
>   }
>   
>