Messages in this thread | | | Date | Wed, 17 Apr 2024 08:50:15 -0500 | Subject | Re: [PATCH v2 25/31] i2c: fsi: Calculate clock divider from local bus frequency | From | Eddie James <> |
| |
On 4/16/24 16:20, Guenter Roeck wrote: > On Tue, Apr 16, 2024 at 01:09:04PM -0500, Eddie James wrote: >> On 4/15/24 17:11, Andi Shyti wrote: >>> Hi Eddie, >>> >>>> @@ -689,6 +692,20 @@ static int fsi_i2c_probe(struct device *dev) >>>> mutex_init(&i2c->lock); >>>> i2c->fsi = to_fsi_dev(dev); >>>> INIT_LIST_HEAD(&i2c->ports); >>>> + i2c->clock_div = I2C_DEFAULT_CLK_DIV; >>>> + >>>> + lbus = fsi_device_local_bus_frequency(i2c->fsi); >>>> + if (lbus) { >>>> + u32 clock = I2C_DEFAULT_CLK_RATE; >>> I don't see the need for initialization. >> >> Does device_property_read_u32 set clock if the property isn't found? If not, >> it needs to be initialized here. Or I can set it in an else statement from >> device_property_read_u32. >> >> >>>> + >>>> + if (!device_property_read_u32(dev, "clock-frequency", &clock)) { >>>> + if (!clock) >>>> + clock = I2C_DEFAULT_CLK_RATE; >>>> + } > if (device_property_read_u32(dev, "clock-frequency", &clock) || !clock) > clock = I2C_DEFAULT_CLK_RATE;
Nice one, thanks.
> >>>> + >>>> + // i2c clock rate = local bus clock / (4 * (i2c clock div + 1)) >>> You forgot to remove this. >> >> I actually meant to leave that comment to explain how the clock rate is >> calculated, as the reverse calculation in the code is a little more >> confusing. >> > Partially that is because you implemented DIV_ROUND_UP() manually.
Thanks Guenter, good point.
Eddie
>>> Andi >>> >>>> + i2c->clock_div = (((lbus + (clock - 1)) / clock) / 4) - 1; > = DIV_ROUND_UP(lbus, clock) / 4 - 1 > > Guenter
| |