On Tue, Apr 5, 2022 at 4:11 PM Neil Armstrong <narmstrong@xxxxxxxxxxxx> wrote: > > Hi, > > On 28/03/2022 23:51, Lucas Tanure wrote: > > > > > > On Mon, 28 Mar 2022, 21:37 Kevin Hilman, <khilman@xxxxxxxxxxxx <mailto:khilman@xxxxxxxxxxxx>> wrote: > > > > Hi Lucas, > > > > Lucas Tanure <tanure@xxxxxxxxx <mailto:tanure@xxxxxxxxx>> writes: > > > > > The default duty cycle of 33% is less than the required > > > by the I2C specs for the LOW period of the SCL clock. > > > > > > So, for 100Khz or less, use 50%H/50%L duty cycle, and > > > for the clock above 100Khz, use 40%H/60%L duty cycle. > > > That ensures the low period of SCL is always more than > > > the minimum required by the specs at any given frequency. > > > > Thanks for the fixes! > > > > This is going to affect all SoCs, so ould you please summarize how your > > changes were tested, and on which SoCs & boards? > > > > Thanks, > > > > Kevin > > > > > > Hi, > > > > I only tested against vim3 board, measured the bus with an saleae logic pro 16. > > The measurements were with 100k, 400k and a few in between frequencies. > > > > Is that enough? > > I did a few measures on the Libre Computer Le Potato S905X board: > > i2c_AO: > > Before the patchset, I got: > - 100KHz: 1.66uS HIGH, 6.75uS LOW, 20%/80%, Freq 118KHz /!\ > - 400KHz: Unable to decode, clock line is invalid, Data line is also invalid > > With the patchset > - 100KHz: 4.25uS HIGH, 6.58uS LOW, 40%/60%, Freq 92KHz > - 400KHz: 0.33uS HIGH, 3.00uS LOW, 10%/90%, Freq 300KHz > > i2c_B: > > Before the patchset, I got: > - 100KHz: 2.25uS HIGH, 5.41uS LOW, 29%/71%, Freq 130KHz /!\ > - 400KHz: 0.42uS HIGH, 1.66uS LOW, 20%/80%, Freq 480KHz /!\ > > With the patchset > - 100KHz: 4.75uS HIGH, 5.42uS LOW, 46%/54%, Freq 98KHz > - 400KHz: 0.66uS HIGH, 2.00uS LOW, 24%/75%, Freq 375KHz > > > So this fixes the frequency, before they were invalid. > And it fixes 400KHz on i2c_AO... > > I do not understand why behavior is different between i2c_AO & i2c_B, they > are feed with the same clock so it should be the same. > > Did you check on both i2c interfaces ? can you share your results ? I only checked I2C interfaces i2c3 and i2c_ao. I will submit a new patch chain with more results. > > Neil > > > > > Thanks > > Lucas > > > > > > >
