Hi Geert,
> > - u32 icccr;
> > + u32 clock_val;
>
> Perhaps use a union to store either icccr or smd?
Yup, can do.
>
> > u8 recovery_icmcr; /* protected by adapter lock */
> > enum rcar_i2c_type devtype;
> > struct i2c_client *slave;
> > @@ -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);
>
> ICCCR2 note 1: "ICCCR2 should be written to prior to writing ICCCR."
Eeks, I remembered it the other way around :/
> > ick = rate / (cdf + 1);
>
> In case of FM+, cdf will be zero, and ick == rate?
Yes.
>
> > @@ -292,34 +324,55 @@ static int rcar_i2c_clock_calculate(struct rcar_i2c_priv *priv)
> > round = (ick + 500000) / 1000000 * sum;
>
> ick == rate if FM+
Yes, does this induce a change here?
> > round = (round + 500) / 1000;
>
> DIV_ROUND_UP()
DIV_ROUND_CLOSEST() I'd say, but I have a seperate patch for that.
> > + if (priv->flags & ID_P_FMPLUS) {
>
> IIUIC, on R-ar Gen3 and later you can use ICCCR2 without FM+, for
> improved accuracy, too?
Yeah, we could do that. It indeed improves accuracy:
old new
100kHz: 97680/100000 99950/100000
400kHz: 373482/400000 399201/400000
Caring about regressions here is a bit over the top, or?
> > + /*
> > + * SMD should be smaller than SCLD and SCHD, we arbitrarily set
> > + * the ratio 1:3. SCHD:SCLD ratio is 1:1, thus:
> > + * SCL = clkp / (8 + SMD * 2 + SCLD + SCHD + F[(ticf + tr + intd) * clkp])
> > + * SCL = clkp / (8 + SMD * 2 + SMD * 3 + SMD * 3 + F[...])
> > + * SCL = clkp / (8 + SMD * 8 + F[...])
> > + */
> > + smd = DIV_ROUND_UP(ick / t.bus_freq_hz - 8 - round, 8);
>
> Perhaps use rate instead of ick?
That's probably cleaner.
> DIV_ROUND_UP(ick, 8 * (t.bus_freq_hz - 8 - round));
This looks like you assumed "ick / (t.bus_freq_hz - 8 - round)" but it
is "(ick / t.bus_freq_hz) - 8 - round"?
> > + scl = ick / (8 + 8 * smd + round);
>
> DIV_ROUND_UP()?
Okay.
> > + if (smd > 0xff) {
> > + dev_err(dev, "it is impossible to calculate best SCL\n");
> > + return -EINVAL;
>
> Perhaps some "goto error", to share with the error handling for non-FM+?
I will check with the refactored code.
> > - dev_dbg(dev, "clk %d/%d(%lu), round %u, CDF:0x%x, SCGD: 0x%x\n",
> > - scl, t.bus_freq_hz, rate, round, cdf, scgd);
> > + dev_dbg(dev, "clk %d/%d(%lu), round %u, SMD:0x%x, SCHD: 0x%x\n",
>
> %u/%u
>
> Perhaps it makes more sense to print SMD and SCHD in decimal?
>
> This also applies to the existing code (CDF/SCGD) you moved into
> the else branch.
Can do. I don't care it is debug output.
> > + if (scgd == 0x40) {
> > + dev_err(dev, "it is impossible to calculate best SCL\n");
> > + return -EINVAL;
>
> This was -EIO before.
I'll squash this into a seperate cleanup patch I have.
Thanks,
Wolfram
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