linux-kernel - Re: [PATCH 03/14] drivers: net: mdio: mdio-ip8064: improve busy wait delay

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Date:   Thu, 22 Apr 2021 18:56:34 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Ansuel Smith <ansuelsmth@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/14] drivers: net: mdio: mdio-ip8064: improve busy wait
 delay



On 4/22/2021 6:47 PM, Ansuel Smith wrote:
> With the use of the qca8k dsa driver, some problem arised related to
> port status detection. With a load on a specific port (for example a
> simple speed test), the driver starts to bheave in a strange way and

s/bheave/behave/

> garbage data is produced. To address this, enlarge the sleep delay and
> address a bug for the reg offset 31 that require additional delay for
> this specific reg.
> 
> Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
> ---
>  drivers/net/mdio/mdio-ipq8064.c | 36 ++++++++++++++++++++-------------
>  1 file changed, 22 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/net/mdio/mdio-ipq8064.c b/drivers/net/mdio/mdio-ipq8064.c
> index 1bd18857e1c5..5bd6d0501642 100644
> --- a/drivers/net/mdio/mdio-ipq8064.c
> +++ b/drivers/net/mdio/mdio-ipq8064.c
> @@ -15,25 +15,26 @@
>  #include <linux/mfd/syscon.h>
>  
>  /* MII address register definitions */
> -#define MII_ADDR_REG_ADDR                       0x10
> -#define MII_BUSY                                BIT(0)
> -#define MII_WRITE                               BIT(1)
> -#define MII_CLKRANGE_60_100M                    (0 << 2)
> -#define MII_CLKRANGE_100_150M                   (1 << 2)
> -#define MII_CLKRANGE_20_35M                     (2 << 2)
> -#define MII_CLKRANGE_35_60M                     (3 << 2)
> -#define MII_CLKRANGE_150_250M                   (4 << 2)
> -#define MII_CLKRANGE_250_300M                   (5 << 2)
> +#define MII_ADDR_REG_ADDR			0x10
> +#define MII_BUSY				BIT(0)
> +#define MII_WRITE				BIT(1)
> +#define MII_CLKRANGE(x)				((x) << 2)
> +#define MII_CLKRANGE_60_100M			MII_CLKRANGE(0)
> +#define MII_CLKRANGE_100_150M			MII_CLKRANGE(1)
> +#define MII_CLKRANGE_20_35M			MII_CLKRANGE(2)
> +#define MII_CLKRANGE_35_60M			MII_CLKRANGE(3)
> +#define MII_CLKRANGE_150_250M			MII_CLKRANGE(4)
> +#define MII_CLKRANGE_250_300M			MII_CLKRANGE(5)
>  #define MII_CLKRANGE_MASK			GENMASK(4, 2)
>  #define MII_REG_SHIFT				6
>  #define MII_REG_MASK				GENMASK(10, 6)
>  #define MII_ADDR_SHIFT				11
>  #define MII_ADDR_MASK				GENMASK(15, 11)
>  
> -#define MII_DATA_REG_ADDR                       0x14
> +#define MII_DATA_REG_ADDR			0x14
>  
> -#define MII_MDIO_DELAY_USEC                     (1000)
> -#define MII_MDIO_RETRY_MSEC                     (10)
> +#define MII_MDIO_DELAY_USEC			(1000)
> +#define MII_MDIO_RETRY_MSEC			(10)

These changes are not related to what you are doing and are just
whitespace cleaning, better not to mix them with functional changes.

>  
>  struct ipq8064_mdio {
>  	struct regmap *base; /* NSS_GMAC0_BASE */
> @@ -65,7 +66,7 @@ ipq8064_mdio_read(struct mii_bus *bus, int phy_addr, int reg_offset)
>  		   ((reg_offset << MII_REG_SHIFT) & MII_REG_MASK);
>  
>  	regmap_write(priv->base, MII_ADDR_REG_ADDR, miiaddr);
> -	usleep_range(8, 10);
> +	usleep_range(10, 13);
>  
>  	err = ipq8064_mdio_wait_busy(priv);
>  	if (err)
> @@ -91,7 +92,14 @@ ipq8064_mdio_write(struct mii_bus *bus, int phy_addr, int reg_offset, u16 data)
>  		   ((reg_offset << MII_REG_SHIFT) & MII_REG_MASK);
>  
>  	regmap_write(priv->base, MII_ADDR_REG_ADDR, miiaddr);
> -	usleep_range(8, 10);
> +
> +	/* For the specific reg 31 extra time is needed or the next
> +	 * read will produce grabage data.

s/grabage/garbage/

> +	 */
> +	if (reg_offset == 31)
> +		usleep_range(30, 43);
> +	else
> +		usleep_range(10, 13);

This is just super weird, presumably register 31 needs to be conditional
to the PHY, or pseudo-PHY being driven here. Not that it would harm, but
waiting an extra 30 to 43 microseconds with a Marvell PHY or Broadcom
PHY or from another vendor would not be necessary.

>  
>  	return ipq8064_mdio_wait_busy(priv);
>  }
> 

-- 
Florian