netdev - Re: [PATCH net-next] mscc: Add LCPLL Reset to VSC8574 Family of phy drivers

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Message-ID: <c8791db0-b036-51c0-c714-676357fd8be1@gmail.com>
Date:   Thu, 23 Jul 2020 14:18:41 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Bryan Whitehead <Bryan.Whitehead@...rochip.com>,
        davem@...emloft.net
Cc:     netdev@...r.kernel.org, UNGLinuxDriver@...rochip.com
Subject: Re: [PATCH net-next] mscc: Add LCPLL Reset to VSC8574 Family of phy
 drivers

On 7/23/20 1:09 PM, Bryan Whitehead wrote:
> The LCPLL Reset sequence is added to the initialization path
> of the VSC8574 Family of phy drivers.
> 
> The LCPLL Reset sequence is known to reduce hardware inter-op
> issues when using the QSGMII MAC interface.
> 
> This patch is submitted to net-next to avoid merging conflicts that
> may arise if submitted to net.
> 
> Signed-off-by: Bryan Whitehead <Bryan.Whitehead@...rochip.com>

Can you copy the PHY library maintainers for future changes such that
this does not escape their review?

> ---
>  drivers/net/phy/mscc/mscc_main.c | 90 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 90 insertions(+)
> 
> diff --git a/drivers/net/phy/mscc/mscc_main.c b/drivers/net/phy/mscc/mscc_main.c
> index a4fbf3a..f2fa221 100644
> --- a/drivers/net/phy/mscc/mscc_main.c
> +++ b/drivers/net/phy/mscc/mscc_main.c
> @@ -929,6 +929,90 @@ static bool vsc8574_is_serdes_init(struct phy_device *phydev)
>  }
>  
>  /* bus->mdio_lock should be locked when using this function */
> +/* Page should already be set to MSCC_PHY_PAGE_EXTENDED_GPIO */
> +static int vsc8574_wait_for_micro_complete(struct phy_device *phydev)
> +{
> +	u16 timeout = 500;
> +	u16 reg18g = 0;
> +
> +	reg18g = phy_base_read(phydev, 18);
> +	while (reg18g & 0x8000) {
> +		timeout--;
> +		if (timeout == 0)
> +			return -1;
> +		usleep_range(1000, 2000);
> +		reg18g = phy_base_read(phydev, 18);

Please consider using phy_read_poll_timeout() instead of open coding
this busy waiting loop.

> +	}
> +
> +	return 0;
> +}
> +
> +/* bus->mdio_lock should be locked when using this function */
> +static int vsc8574_reset_lcpll(struct phy_device *phydev)
> +{
> +	u16 reg_val = 0;
> +	int ret = 0;
> +
> +	phy_base_write(phydev, MSCC_EXT_PAGE_ACCESS,
> +		       MSCC_PHY_PAGE_EXTENDED_GPIO);
> +
> +	/* Read LCPLL config vector into PRAM */
> +	phy_base_write(phydev, 18, 0x8023);
> +	ret = vsc8574_wait_for_micro_complete(phydev);
> +	if (ret)
> +		goto done;

It might make sense to write a helper function that encapsulates the:

- phy_base_write()
- wait_for_complete

pattern and use it throughout, with an option delay range argument so
you can put that in there, too.
-- 
Florian