netdev - Re: [PATCH net-next v3 3/3] net: dp83869: Add speed optimization feature

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Message-ID: <20200905113818.7962b6d4@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Sat, 5 Sep 2020 11:38:18 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Dan Murphy <dmurphy@...com>
Cc:     <davem@...emloft.net>, <andrew@...n.ch>, <f.fainelli@...il.com>,
        <hkallweit1@...il.com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v3 3/3] net: dp83869: Add speed optimization
 feature

On Thu, 3 Sep 2020 06:42:59 -0500 Dan Murphy wrote:
> +static int dp83869_set_downshift(struct phy_device *phydev, u8 cnt)
> +{
> +	int val, count;
> +
> +	if (cnt > DP83869_DOWNSHIFT_8_COUNT)
> +		return -E2BIG;

ERANGE

> +	if (!cnt)
> +		return phy_clear_bits(phydev, DP83869_CFG2,
> +				      DP83869_DOWNSHIFT_EN);
> +
> +	switch (cnt) {
> +	case DP83869_DOWNSHIFT_1_COUNT:
> +		count = DP83869_DOWNSHIFT_1_COUNT_VAL;
> +		break;
> +	case DP83869_DOWNSHIFT_2_COUNT:
> +		count = DP83869_DOWNSHIFT_2_COUNT_VAL;
> +		break;
> +	case DP83869_DOWNSHIFT_4_COUNT:
> +		count = DP83869_DOWNSHIFT_4_COUNT_VAL;
> +		break;
> +	case DP83869_DOWNSHIFT_8_COUNT:
> +		count = DP83869_DOWNSHIFT_8_COUNT_VAL;
> +		break;
> +	default:
> +		phydev_err(phydev,
> +			   "Downshift count must be 1, 2, 4 or 8\n");
> +		return -EINVAL;
> +	}
> +
> +	val = DP83869_DOWNSHIFT_EN;
> +	val |= FIELD_PREP(DP83869_DOWNSHIFT_ATTEMPT_MASK, count);
> +
> +	return phy_modify(phydev, DP83869_CFG2,
> +			  DP83869_DOWNSHIFT_EN | DP83869_DOWNSHIFT_ATTEMPT_MASK,
> +			  val);
> +}