linux-kernel - Re: [PATCH v5 3/5] bnx2x: Eliminate duplicate barriers on weakly-ordered archs

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Date:   Fri, 23 Mar 2018 12:20:35 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     okaya@...eaurora.org
Cc:     netdev@...r.kernel.org, timur@...eaurora.org,
        sulrich@...eaurora.org, linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, ariel.elior@...ium.com,
        everest-linux-l2@...ium.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 3/5] bnx2x: Eliminate duplicate barriers on
 weakly-ordered archs

From: Sinan Kaya <okaya@...eaurora.org>
Date: Thu, 22 Mar 2018 13:10:00 -0400

> Code includes wmb() followed by writel(). writel() already has a
> barrier on some architectures like arm64.
 ...
> @@ -4155,7 +4155,7 @@ netdev_tx_t bnx2x_start_xmit(struct sk_buff *skb, struct net_device *dev)
>  	txdata->tx_db.data.prod += nbd;
>  	barrier();
>  
> -	DOORBELL(bp, txdata->cid, txdata->tx_db.raw);
> +	DOORBELL_RELAXED(bp, txdata->cid, txdata->tx_db.raw);
>  
>  	mmiowb();
 ...
> @@ -2592,7 +2592,7 @@ static int bnx2x_run_loopback(struct bnx2x *bp, int loopback_mode)
>  
>  	txdata->tx_db.data.prod += 2;
>  	barrier();
> -	DOORBELL(bp, txdata->cid, txdata->tx_db.raw);
> +	DOORBELL_RELAXED(bp, txdata->cid, txdata->tx_db.raw);

These are compiler barriers being used here, not wmb().

Look, if I can't see a clear:

	wmb()
	writel()

sequence in the patch hunks, I am going to keep pushing back on
these changes.

Thank you.