netdev - Re: [PATCH v2 net 3/6] net: enetc: take the MDIO lock only once per NAPI poll cycle

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Message-ID: <YDgqI8eGDpJKxiLY@lunn.ch>
Date:   Thu, 25 Feb 2021 23:52:19 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        Michael Walle <michael@...le.cc>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandru Marginean <alexandru.marginean@....com>,
        Vladimir Oltean <vladimir.oltean@....com>
Subject: Re: [PATCH v2 net 3/6] net: enetc: take the MDIO lock only once per
 NAPI poll cycle

On Thu, Feb 25, 2021 at 02:18:32PM +0200, Vladimir Oltean wrote:
> @@ -327,8 +329,8 @@ static void enetc_get_tx_tstamp(struct enetc_hw *hw, union enetc_tx_bd *txbd,
>  {
>  	u32 lo, hi, tstamp_lo;
>  
> -	lo = enetc_rd(hw, ENETC_SICTR0);
> -	hi = enetc_rd(hw, ENETC_SICTR1);
> +	lo = enetc_rd_hot(hw, ENETC_SICTR0);
> +	hi = enetc_rd_hot(hw, ENETC_SICTR1);
>  	tstamp_lo = le32_to_cpu(txbd->wb.tstamp);
>  	if (lo <= tstamp_lo)
>  		hi -= 1;

Hi Vladimir

This change is not obvious, and there is no mention of it in the
commit message. Please could you explain it. I guess it is to do with
enetc_get_tx_tstamp() being called with the MDIO lock held now, when
it was not before?

Thanks
	Andrew