linux-kernel - Re: [PATCH] net: macb: Write only necessary bits in NCR in macb reset

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Message-ID: <ddb3f476-928d-e235-3e7e-e78434074b04@atmel.com>
Date:   Mon, 28 Nov 2016 10:31:07 +0100
From:   Nicolas Ferre <nicolas.ferre@...el.com>
To:     Harini Katakam <harini.katakam@...inx.com>, <davem@...emloft.net>,
        <harinikatakamlinux@...il.com>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <harinik@...inx.com>, <michals@...inx.com>
Subject: Re: [PATCH] net: macb: Write only necessary bits in NCR in macb reset

Le 28/11/2016 à 10:23, Harini Katakam a écrit :
> In macb_reset_hw, use read-modify-write to disable RX and TX.
> This way exiting settings and reserved bits wont be disturbed.

Yes, indeed... but I would have liked a line about how you discovered it
was an issue for you ;  what did it break, etc...

> Use the same method for clearing statistics as well.
> 
> Signed-off-by: Harini Katakam <harinik@...inx.com>
> ---
>  drivers/net/ethernet/cadence/macb.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
> index 0e489bb..80ccfc4 100644
> --- a/drivers/net/ethernet/cadence/macb.c
> +++ b/drivers/net/ethernet/cadence/macb.c
> @@ -1743,15 +1743,18 @@ static void macb_init_rings(struct macb *bp)
>  static void macb_reset_hw(struct macb *bp)
>  {
>  	struct macb_queue *queue;
> -	unsigned int q;
> +	unsigned int q, ctrl;

I would have preferred a different line with u32 type.


>  	/* Disable RX and TX (XXX: Should we halt the transmission
>  	 * more gracefully?)
>  	 */
> -	macb_writel(bp, NCR, 0);
> +	ctrl = macb_readl(bp, NCR);
> +	ctrl &= ~(MACB_BIT(RE) | MACB_BIT(TE));
> +	macb_writel(bp, NCR, ctrl);
>  
>  	/* Clear the stats registers (XXX: Update stats first?) */
> -	macb_writel(bp, NCR, MACB_BIT(CLRSTAT));
> +	ctrl |= MACB_BIT(CLRSTAT);
> +	macb_writel(bp, NCR, ctrl);
>  
>  	/* Clear all status flags */
>  	macb_writel(bp, TSR, -1);
> 


-- 
Nicolas Ferre