linux-kernel - Re: [PATCH net-next 3/4] net: phy: mscc-miim: improve waiting logic

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Message-ID: <20200526210734.GI3972@piout.net>
Date:   Tue, 26 May 2020 23:07:34 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Antoine Tenart <antoine.tenart@...tlin.com>
Cc:     davem@...emloft.net, andrew@...n.ch, f.fainelli@...il.com,
        hkallweit1@...il.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, thomas.petazzoni@...tlin.com,
        allan.nielsen@...rochip.com
Subject: Re: [PATCH net-next 3/4] net: phy: mscc-miim: improve waiting logic

On 26/05/2020 18:22:55+0200, Antoine Ténart wrote:
> The MSCC MIIM MDIO driver uses a waiting logic to wait for the MDIO bus
> to be ready to accept next commands. It does so by polling the BUSY
> status bit which indicates the MDIO bus has completed all pending
> operations. This can take time, and the controller supports writing the
> next command as soon as there are no pending commands (which happens
> while the MDIO bus is busy completing its current command).
> 
> This patch implements this improved logic by adding an helper to poll
> the PENDING status bit, and by adjusting where we should wait for the
> bus to not be busy or to not be pending.
> 
> Signed-off-by: Antoine Tenart <antoine.tenart@...tlin.com>
Reviewed-by: Alexandre Belloni <alexandre.belloni@...tlin.com>

> ---
>  drivers/net/phy/mdio-mscc-miim.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/phy/mdio-mscc-miim.c b/drivers/net/phy/mdio-mscc-miim.c
> index 42119f661452..aed9afa1e8f1 100644
> --- a/drivers/net/phy/mdio-mscc-miim.c
> +++ b/drivers/net/phy/mdio-mscc-miim.c
> @@ -16,6 +16,7 @@
>  #include <linux/of_mdio.h>
>  
>  #define MSCC_MIIM_REG_STATUS		0x0
> +#define		MSCC_MIIM_STATUS_STAT_PENDING	BIT(2)
>  #define		MSCC_MIIM_STATUS_STAT_BUSY	BIT(3)
>  #define MSCC_MIIM_REG_CMD		0x8
>  #define		MSCC_MIIM_CMD_OPR_WRITE		BIT(1)
> @@ -47,13 +48,23 @@ static int mscc_miim_wait_ready(struct mii_bus *bus)
>  				  !(val & MSCC_MIIM_STATUS_STAT_BUSY), 50, 10000);
>  }
>  
> +static int mscc_miim_wait_pending(struct mii_bus *bus)
> +{
> +	struct mscc_miim_dev *miim = bus->priv;
> +	u32 val;
> +
> +	return readl_poll_timeout(miim->regs + MSCC_MIIM_REG_STATUS, val,
> +				  !(val & MSCC_MIIM_STATUS_STAT_PENDING),
> +				  50, 10000);
> +}
> +
>  static int mscc_miim_read(struct mii_bus *bus, int mii_id, int regnum)
>  {
>  	struct mscc_miim_dev *miim = bus->priv;
>  	u32 val;
>  	int ret;
>  
> -	ret = mscc_miim_wait_ready(bus);
> +	ret = mscc_miim_wait_pending(bus);
>  	if (ret)
>  		goto out;
>  
> @@ -82,7 +93,7 @@ static int mscc_miim_write(struct mii_bus *bus, int mii_id,
>  	struct mscc_miim_dev *miim = bus->priv;
>  	int ret;
>  
> -	ret = mscc_miim_wait_ready(bus);
> +	ret = mscc_miim_wait_pending(bus);
>  	if (ret < 0)
>  		goto out;
>  
> -- 
> 2.26.2
> 

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com