netdev - Re: [net-next PATCH v3 01/14] net: dsa: qca8k: cache match data to speed up access

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Date:   Sun, 24 Jul 2022 22:42:20 +0200
From:   Christian Marangi <ansuelsmth@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [net-next PATCH v3 01/14] net: dsa: qca8k: cache match data to
 speed up access

On Mon, Jul 25, 2022 at 02:06:26AM +0300, Vladimir Oltean wrote:
> On Sun, Jul 24, 2022 at 10:27:13PM +0200, Christian Marangi wrote:
> > > > diff --git a/drivers/net/dsa/qca/qca8k.c b/drivers/net/dsa/qca/qca8k.c
> > > > index 1cbb05b0323f..212b284f9f73 100644
> > > > --- a/drivers/net/dsa/qca/qca8k.c
> > > > +++ b/drivers/net/dsa/qca/qca8k.c
> > > > @@ -3168,6 +3155,11 @@ qca8k_sw_probe(struct mdio_device *mdiodev)
> > > >  	if (ret)
> > > >  		return ret;
> > > >  
> > > > +	/* Cache match data in priv struct.
> > > > +	 * Match data is already checked in read_switch_id.
> > > > +	 */
> > > > +	priv->info = of_device_get_match_data(priv->dev);
> > > > +
> > > 
> > > So why don't you set priv->info right before calling qca8k_read_switch_id(),
> > > then?
> > > 
> > 
> > The idea was to make the read_switch_id a function to check if the
> > switch is compatible... But yhea now that i think about it doesn't
> > really make sense.
> 
> I am not saying qca8k_read_switch_id() should do anything more than
> reading the switch id. I am saying why can't qca8k_read_switch_id()
> already find priv->info be pre-populated, just like any other function.
> Why don't you set priv->info a lot earlier, see below.
>

Sure, it was just a stupid idea to set everything not strictly neeeded
only after verifying that we have a correct switch... But it doesn't
make sense as qca8k_priv is freed anyway if that's the case.

Will do the change in v5.

> diff --git a/drivers/net/dsa/qca/qca8k-8xxx.c b/drivers/net/dsa/qca/qca8k-8xxx.c
> index fa91517e930b..590ff810c95e 100644
> --- a/drivers/net/dsa/qca/qca8k-8xxx.c
> +++ b/drivers/net/dsa/qca/qca8k-8xxx.c
> @@ -1892,6 +1892,7 @@ qca8k_sw_probe(struct mdio_device *mdiodev)
>  
>  	priv->bus = mdiodev->bus;
>  	priv->dev = &mdiodev->dev;
> +	priv->info = of_device_get_match_data(priv->dev);
>  
>  	priv->reset_gpio = devm_gpiod_get_optional(priv->dev, "reset",
>  						   GPIOD_ASIS);
> @@ -1924,11 +1925,6 @@ qca8k_sw_probe(struct mdio_device *mdiodev)
>  	if (ret)
>  		return ret;
>  
> -	/* Cache match data in priv struct.
> -	 * Match data is already checked in read_switch_id.
> -	 */
> -	priv->info = of_device_get_match_data(priv->dev);
> -
>  	priv->ds = devm_kzalloc(&mdiodev->dev, sizeof(*priv->ds), GFP_KERNEL);
>  	if (!priv->ds)
>  		return -ENOMEM;
> diff --git a/drivers/net/dsa/qca/qca8k-common.c b/drivers/net/dsa/qca/qca8k-common.c
> index e6294d6a7b8f..8f634edc52c2 100644
> --- a/drivers/net/dsa/qca/qca8k-common.c
> +++ b/drivers/net/dsa/qca/qca8k-common.c
> @@ -1211,23 +1211,19 @@ qca8k_port_lag_leave(struct dsa_switch *ds, int port,
>  
>  int qca8k_read_switch_id(struct qca8k_priv *priv)
>  {
> -	const struct qca8k_match_data *data;
>  	u32 val;
>  	u8 id;
>  	int ret;
>  
> -	/* get the switches ID from the compatible */
> -	data = of_device_get_match_data(priv->dev);
> -	if (!data)
> -		return -ENODEV;
> -
>  	ret = qca8k_read(priv, QCA8K_REG_MASK_CTRL, &val);
>  	if (ret < 0)
>  		return -ENODEV;
>  
>  	id = QCA8K_MASK_CTRL_DEVICE_ID(val);
> -	if (id != data->id) {
> -		dev_err(priv->dev, "Switch id detected %x but expected %x", id, data->id);
> +	if (id != priv->info->id) {
> +		dev_err(priv->dev,
> +			"Switch id detected %x but expected %x",
> +			id, priv->info->id);
>  		return -ENODEV;
>  	}
>  
> 
> Also note how the "Switch id detected ... but expected ..." message
> lacks a trailing \n.
> 

Will fix this when the read_switch_id function is moved to common file.

> > (Just for reference I just sent v4 as I got a report from kernel test
> > bot... it's really just this series with a change in 0002 patch that set
> > the struct for ops as a pointer... didn't encounter this with gcc but it
> > seems kernel test bot use some special config...)
> 
> Yea, I was still kinda reviewing v3... Anyway, now you'll have to wait
> for me to finish my v3 feedback on the v4, and then send the v5 after at
> least 24 more hours.

Sure and sorry for the mess.

-- 
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