linux-kernel - Re: [PATCH 3/3] i2c: rcar: add FastMode+ support

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Message-ID: <20230906073417.y2xpj6o2g5r7p5nu@zenone.zhora.eu>
Date:   Wed, 6 Sep 2023 09:34:17 +0200
From:   Andi Shyti <andi.shyti@...nel.org>
To:     Wolfram Sang <wsa+renesas@...g-engineering.com>,
        linux-renesas-soc@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] i2c: rcar: add FastMode+ support

Hi Wolfram,

> > > @@ -217,7 +228,17 @@ static void rcar_i2c_init(struct rcar_i2c_priv *priv)
> > >  	rcar_i2c_write(priv, ICMCR, MDBS);
> > >  	rcar_i2c_write(priv, ICMSR, 0);
> > >  	/* start clock */
> > > -	rcar_i2c_write(priv, ICCCR, priv->icccr);
> > > +	if (priv->flags & ID_P_FMPLUS) {
> > > +		rcar_i2c_write(priv, ICCCR, 0);
> > > +		rcar_i2c_write(priv, ICMPR, priv->clock_val);
> > > +		rcar_i2c_write(priv, ICHPR, 3 * priv->clock_val);
> > > +		rcar_i2c_write(priv, ICLPR, 3 * priv->clock_val);
> > > +		rcar_i2c_write(priv, ICCCR2, FMPE | CDFD | HLSE | SME);
> > > +	} else {
> > > +		rcar_i2c_write(priv, ICCCR, priv->clock_val);
> > > +		if (priv->devtype >= I2C_RCAR_GEN3)
> > > +			rcar_i2c_write(priv, ICCCR2, 0);
> > 
> > is this last bit part of the FM+ enabling or is it part of the
> > GEN4 support?
> 
> It is "disabling FM+" for lower speeds. Since we never used ICCCR2
> before FM+, we need to make sure it is cleared properly.

OK... I'm missing some hardware details here :)

> > > +		for (scgd = 0; scgd < 0x40; scgd++) {
> > > +			scl = ick / (20 + (scgd * 8) + round);
> > > +			if (scl <= t.bus_freq_hz)
> > > +				break;
> > > +		}
> > > +
> > > +		if (scgd == 0x40) {
> > 
> > would be nice to give a meaning to this 0x40 constant... either
> > having it in a define or a comment, at least.
> 
> This code existed before and was just moved into an if-body. It will be
> updated in another series following this one.

OK, thanks!

Reviewed-by: Andi Shyti <andi.shyti@...nel.org> 

Andi