Messages in this thread | | | Date | Wed, 6 Sep 2023 14:11:00 +0200 | From | Wolfram Sang <> | Subject | Re: [PATCH 3/3] i2c: rcar: add FastMode+ support |
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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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