netdev - Re: [PATCH] net: phy: broadcom: add support for BCM5221 phy

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Message-ID: <e627f60f-b13d-d82f-ff7c-f4b2bef21303@benettiengineering.com>
Date: Sat, 12 Aug 2023 19:15:39 +0200
From: Giulio Benetti <giulio.benetti@...ettiengineering.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>, Andrew Lunn <andrew@...n.ch>,
 Heiner Kallweit <hkallweit1@...il.com>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Florian Fainelli <florian.fainelli@...adcom.com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, Jim Reinhart <jimr@...vox.com>,
 James Autry <jautry@...vox.com>, Matthew Maron <matthewm@...vox.com>
Subject: Re: [PATCH] net: phy: broadcom: add support for BCM5221 phy

Hello Russell,

thanks for reviewing,

On 12/08/23 00:22, Russell King (Oracle) wrote:
> On Fri, Aug 11, 2023 at 11:53:22PM +0200, Giulio Benetti wrote:
>> +	reg = phy_read(phydev, MII_BRCM_FET_INTREG);
>> +	if (reg < 0)
>> +		return reg;
>> +
>> +	/* Unmask events we are interested in and mask interrupts globally. */
>> +	reg = MII_BRCM_FET_IR_ENABLE |
>> +	      MII_BRCM_FET_IR_MASK;
>> +
>> +	err = phy_write(phydev, MII_BRCM_FET_INTREG, reg);
>> +	if (err < 0)
>> +		return err;
> 
> Please explain why you read MII_BRCM_FET_INTREG, then discard its value
> and write a replacement value.

ok, yes, as it is it doesn't look self-explanatory at all

>> +
>> +	/* Enable auto MDIX */
>> +	err = phy_clear_bits(phydev, BCM5221_AEGSR, BCM5221_AEGSR_MDIX_DIS);
>> +	if (err < 0)
>> +		return err;
>> +
>> +	/* Enable shadow register access */
>> +	brcmtest = phy_read(phydev, MII_BRCM_FET_BRCMTEST);
>> +	if (brcmtest < 0)
>> +		return brcmtest;
>> +
>> +	reg = brcmtest | MII_BRCM_FET_BT_SRE;
>> +
>> +	err = phy_write(phydev, MII_BRCM_FET_BRCMTEST, reg);
>> +	if (err < 0)
>> +		return err;
> 
> I think you should consider locking the MDIO bus while the device is
> switched to the shadow register set, so that other accesses don't happen
> that may interfere with this.

oh, I haven't considered this, you're totally right,

>> +static int bcm5221_suspend(struct phy_device *phydev)
>> +{
>> +	int reg, err, err2, brcmtest;
>> +
>> +	/* Enable shadow register access */
>> +	brcmtest = phy_read(phydev, MII_BRCM_FET_BRCMTEST);
>> +	if (brcmtest < 0)
>> +		return brcmtest;
>> +
>> +	reg = brcmtest | MII_BRCM_FET_BT_SRE;
>> +
>> +	err = phy_write(phydev, MII_BRCM_FET_BRCMTEST, reg);
>> +	if (err < 0)
>> +		return err;
>> +
>> +	/* Force Low Power Mode with clock enabled */
>> +	err = phy_set_bits(phydev, MII_BRCM_FET_SHDW_AUXMODE4,
>> +			   BCM5221_SHDW_AM4_EN_CLK_LPM |
>> +			   BCM5221_SHDW_AM4_FORCE_LPM);
>> +
>> +	/* Disable shadow register access */
>> +	err2 = phy_write(phydev, MII_BRCM_FET_BRCMTEST, brcmtest);
>> +	if (!err)
>> +		err = err2;
> 
> Same here.

ok,

>> +
>> +	return err;
>> +}
>> +
>> +static int bcm5221_resume(struct phy_device *phydev)
>> +{
>> +	int reg, err, err2, brcmtest;
>> +
>> +	/* Enable shadow register access */
>> +	brcmtest = phy_read(phydev, MII_BRCM_FET_BRCMTEST);
>> +	if (brcmtest < 0)
>> +		return brcmtest;
>> +
>> +	reg = brcmtest | MII_BRCM_FET_BT_SRE;
>> +
>> +	err = phy_write(phydev, MII_BRCM_FET_BRCMTEST, reg);
>> +	if (err < 0)
>> +		return err;
>> +
>> +	/* Exit Low Power Mode with clock enabled */
>> +	err = phy_clear_bits(phydev, MII_BRCM_FET_SHDW_AUXMODE4,
>> +			     BCM5221_SHDW_AM4_FORCE_LPM);
>> +
>> +	/* Disable shadow register access */
>> +	err2 = phy_write(phydev, MII_BRCM_FET_BRCMTEST, brcmtest);
>> +	if (!err)
>> +		err = err2;
> 
> And, of course, same here.

ok, will do on V2 along with the other point from Andrew and Florian.

Thanks again for the review,
Best regards
-- 
Giulio Benetti
CEO&CTO@...etti Engineering sas