linux-kernel - Re: [PATCH 1/2] drivers: net: mdio-sun4i: Speedup mdio read and write

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Date:   Tue, 06 Sep 2022 21:52:24 +0200
From:   Jernej Škrabec <jernej.skrabec@...il.com>
To:     linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org,
        qianfanguijin@....com
Cc:     Maxime Ripard <mripard@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        linux-arm-kernel@...ts.infradead.org,
        Evgeny Boger <boger@...enboard.com>,
        qianfan Zhao <qianfanguijin@....com>
Subject: Re: [PATCH 1/2] drivers: net: mdio-sun4i: Speedup mdio read and write

Dne torek, 06. september 2022 ob 09:56:15 CEST je qianfanguijin@....com 
napisal(a):
> From: qianfan Zhao <qianfanguijin@....com>
> 
> msleep(1) on my board takes about 30ms, and it is too long to accept.
> Use read_poll_timeout to speedup.
> 
> Signed-off-by: qianfan Zhao <qianfanguijin@....com>
> ---
>  drivers/net/mdio/mdio-sun4i.c | 29 ++++++++++++-----------------
>  1 file changed, 12 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/net/mdio/mdio-sun4i.c b/drivers/net/mdio/mdio-sun4i.c
> index f798de3276dc..168e2a375535 100644
> --- a/drivers/net/mdio/mdio-sun4i.c
> +++ b/drivers/net/mdio/mdio-sun4i.c
> @@ -26,8 +26,6 @@
>  #define EMAC_MAC_MIND_REG	(0x10)
>  #define EMAC_MAC_SSRR_REG	(0x14)
> 
> -#define MDIO_TIMEOUT		(msecs_to_jiffies(100))
> -
>  struct sun4i_mdio_data {
>  	void __iomem		*membase;
>  	struct regulator	*regulator;
> @@ -36,8 +34,7 @@ struct sun4i_mdio_data {
>  static int sun4i_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
>  {
>  	struct sun4i_mdio_data *data = bus->priv;
> -	unsigned long timeout_jiffies;
> -	int value;
> +	int ret, tmp, value;
> 
>  	/* issue the phy address and reg */
>  	writel((mii_id << 8) | regnum, data->membase + EMAC_MAC_MADR_REG);
> @@ -45,12 +42,11 @@ static int sun4i_mdio_read(struct mii_bus *bus, int
> mii_id, int regnum) writel(0x1, data->membase + EMAC_MAC_MCMD_REG);
> 
>  	/* Wait read complete */
> -	timeout_jiffies = jiffies + MDIO_TIMEOUT;
> -	while (readl(data->membase + EMAC_MAC_MIND_REG) & 0x1) {
> -		if (time_is_before_jiffies(timeout_jiffies))
> -			return -ETIMEDOUT;
> -		msleep(1);
> -	}
> +	ret = read_poll_timeout(readl, tmp, (tmp & 1) == 0,
> +				20, 10000, false,
> +				data->membase + 
EMAC_MAC_MIND_REG);

You should use readl_poll_timeout() instead, as instructed by documentation. 
Additionally, are you sure about both delay parameters? They are both much 
smaller than in original code.

Same comments apply to patch 2.

Best regards,
Jernej

> +	if (ret < 0)
> +		return ret;
> 
>  	/* push down the phy io line */
>  	writel(0x0, data->membase + EMAC_MAC_MCMD_REG);
> @@ -64,7 +60,7 @@ static int sun4i_mdio_write(struct mii_bus *bus, int
> mii_id, int regnum, u16 value)
>  {
>  	struct sun4i_mdio_data *data = bus->priv;
> -	unsigned long timeout_jiffies;
> +	int ret, tmp;
> 
>  	/* issue the phy address and reg */
>  	writel((mii_id << 8) | regnum, data->membase + EMAC_MAC_MADR_REG);
> @@ -72,12 +68,11 @@ static int sun4i_mdio_write(struct mii_bus *bus, int
> mii_id, int regnum, writel(0x1, data->membase + EMAC_MAC_MCMD_REG);
> 
>  	/* Wait read complete */
> -	timeout_jiffies = jiffies + MDIO_TIMEOUT;
> -	while (readl(data->membase + EMAC_MAC_MIND_REG) & 0x1) {
> -		if (time_is_before_jiffies(timeout_jiffies))
> -			return -ETIMEDOUT;
> -		msleep(1);
> -	}
> +	ret = read_poll_timeout(readl, tmp, (tmp & 1) == 0,
> +				20, 10000, false,
> +				data->membase + 
EMAC_MAC_MIND_REG);
> +	if (ret < 0)
> +		return ret;
> 
>  	/* push down the phy io line */
>  	writel(0x0, data->membase + EMAC_MAC_MCMD_REG);
> --
> 2.25.1