netdev - Re: [net-next RFC PATCH v4 15/15] net: dsa: qca8k: cache lo and hi for mdio write

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Date:   Sat, 11 Dec 2021 20:04:42 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Ansuel Smith <ansuelsmth@...il.com>, 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>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [net-next RFC PATCH v4 15/15] net: dsa: qca8k: cache lo and hi
 for mdio write



On 12/11/2021 11:57 AM, Ansuel Smith wrote:
>  From Documentation, we can cache lo and hi the same way we do with the
> page. This massively reduce the mdio write as 3/4 of the time we only
> require to write the lo or hi part for a mdio write.
> 
> Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
> ---
>   drivers/net/dsa/qca8k.c | 49 ++++++++++++++++++++++++++++++++++++-----
>   1 file changed, 44 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
> index 375a1d34e46f..b109a74031c6 100644
> --- a/drivers/net/dsa/qca8k.c
> +++ b/drivers/net/dsa/qca8k.c
> @@ -94,6 +94,48 @@ qca8k_split_addr(u32 regaddr, u16 *r1, u16 *r2, u16 *page)
>   	*page = regaddr & 0x3ff;
>   }
>   
> +static u16 qca8k_current_lo = 0xffff;

Let's assume I have two qca8k switches in my system on the same or a 
different MDIO bus, is not the caching supposed to be a per-qca8k switch 
instance thing?

> +
> +static int
> +qca8k_set_lo(struct mii_bus *bus, int phy_id, u32 regnum, u16 lo)
> +{
> +	int ret;
> +
> +	if (lo == qca8k_current_lo) {
> +		// pr_info("SAME LOW");

Stray debugging left.

> +		return 0;
> +	}
> +
> +	ret = bus->write(bus, phy_id, regnum, lo);
> +	if (ret < 0)
> +		dev_err_ratelimited(&bus->dev,
> +				    "failed to write qca8k 32bit lo register\n");
> +
> +	qca8k_current_lo = lo;
> +	return 0;
> +}
> +
> +static u16 qca8k_current_hi = 0xffff;
> +
> +static int
> +qca8k_set_hi(struct mii_bus *bus, int phy_id, u32 regnum, u16 hi)
> +{
> +	int ret;
> +
> +	if (hi == qca8k_current_hi) {
> +		// pr_info("SAME HI");

Likewise
-- 
Florian