linux-kernel - Re: [PATCH net-next 04/12] net: pse-pd: tps23881: Add support for power limit and measurement features

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Message-ID: <20241009110501.5f776c9b@kmaincent-XPS-13-7390>
Date: Wed, 9 Oct 2024 11:05:01 +0200
From: Kory Maincent <kory.maincent@...tlin.com>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
 <pabeni@...hat.com>, Jonathan Corbet <corbet@....net>, Donald Hunter
 <donald.hunter@...il.com>, Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
 linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
 linux-doc@...r.kernel.org, Kyle Swenson <kyle.swenson@....tech>, Dent
 Project <dentproject@...uxfoundation.org>, kernel@...gutronix.de
Subject: Re: [PATCH net-next 04/12] net: pse-pd: tps23881: Add support for
 power limit and measurement features

On Wed, 9 Oct 2024 07:02:38 +0200
Oleksij Rempel <o.rempel@...gutronix.de> wrote:

> On Wed, Oct 02, 2024 at 06:28:00PM +0200, Kory Maincent wrote:
> > From: Kory Maincent (Dent Project) <kory.maincent@...tlin.com>
> > 
> > Expand PSE callbacks to support the newly introduced
> > pi_get/set_current_limit() and pi_get_voltage() functions. These callbacks
> > allow for power limit configuration in the TPS23881 controller.
> > 
> > Additionally, the patch includes the detected class, the current power
> > delivered and the power limit ranges in the status returned, providing more
> > comprehensive PoE status reporting.
> > 
> > Signed-off-by: Kory Maincent <kory.maincent@...tlin.com>  
> 
> > +static int tps23881_pi_get_class(struct tps23881_priv *priv, int id)
> > +{  
> ....
> > +	if (chan < 4)
> > +		class = ret >> 4;
> > +	else
> > +		class = ret >> 12;  
> 
> ....
> > +tps23881_pi_set_2p_pw_limit(struct tps23881_priv *priv, u8 chan, u8 pol)
> > +{  
> ....
> > +	reg = TPS23881_REG_2PAIR_POL1 + (chan % 4);
> > +	ret = i2c_smbus_read_word_data(client, reg);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	if (chan < 4)
> > +		val = (ret & 0xff00) | pol;
> > +	else
> > +		val = (ret & 0xff) | (pol << 8);  
> 
> This is a common pattern in this driver, we read and write two registers
> in one run and then calculate bit offset for the channel, can you please
> move it in to separate function. This can be done in a separate patch if
> you like.

The pattern is common but the operations are always different so I didn't found
a clean way of doing it.
Here is a listing of it:
	if (chan < 4)
		class = ret >> 4;
	else
		class = ret >> 12;

	if (chan < 4)
		val = (ret & 0xff00) | pol;
	else
		val = (ret & 0xff) | (pol << 8);  

        if (chan < 4)                                                           
                val = (u16)(ret | BIT(chan));                                   
        else                                                                    
                val = (u16)(ret | BIT(chan + 4));

	if (chan < 4)
		mW = (ret & 0xff) * TPS23881_MW_STEP;
	else
		mW = (ret >> 8) * TPS23881_MW_STEP;


Any idea?

Regards,
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com