Am Montag, 16. Mai 2016, 13:09:31 schrieb Douglas Anderson: > From: David Wu <david.wu@xxxxxxxxxxxxxx> > > We've got 9 (count em!) i2c controllers on rk3399, some of which are in > the PMU power domain and some of which are normal peripherals. Add them > all to the main rk3399 dtsi file so future patches can turn them on in > the board dts files. > > Note: by default we try to set the i2c clock rate to 200 MHz so that we > can achieve good i2c functional clock rates. 200 MHz gives us the > ability to make very close to 100 kHz / 400 kHz / 1 MHz rates. If > boards want to tune clock rates further they can always override. > Possibly boards could want to tune this if: > - they wanted to save an infinitesimal amount of power and they knew > their i2c bus was slow anyway. Since we gate the functional clock > when the i2c bus is not active, power savings would only be while i2c > transfers were happening and probably won't be very big anyway. > - they wanted to eek out a bit more speed by carefully tuning the source > clock to make divisions work out perfectly, accounting for the rise / > fall time measured on an actual board. > > Note also that we still request 200 MHz for the PMU i2c busses even > though we expect that we won't make that exactly (currently PPLL is 676 > MHz which gives us 169 MHz). > > Signed-off-by: David Wu <david.wu@xxxxxxxxxxxxxx> > Signed-off-by: Jianqun Xu <jay.xu@xxxxxxxxxxxxxx> > [dianders: wrote desc; put in assigned-clocks; reordered nodes] > Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx> applied to my dts64 branch for 4.8 Thanks Heiko -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
