Hi, Wolfram, On 29.01.2024 12:55, Wolfram Sang wrote: > Hi Claudiu, > > but one thing I can ask already: > >> Investigating it on RZ/G3S lead to the conclusion that every time the issue >> is reproduced all the probed TAPs are OK. According to datasheet, when this >> happens the change point of data need to be considered for tuning. > > Yes, "considered" means here it should be *avoided*. My understanding was the other way around from this statement found in RZ/G3S hw manual: "If all of the TAP [i] is OK, the sampling clock position is selected by identifying the change point of data. Change point of the data can be found in the value of SCC_SMPCMP register. Usage example is Section 33.8.3, Change point of the input data." > >> Previous code considered the change point of data happens when the content >> of the SMPCMP register is zero. According to RZ/V2M hardware manual, > > When SMPCMP is zero, there is *no* change point. Which is good. That was my understanding, too. > >> chapter "Change Point of the Input Data" (as this is the most clear >> description that I've found about change point of the input data and all >> RZ hardware manual are similar on this chapter), > > I also have a chapter named like this. If you check the diagram, change > point is between TAP2 and 3, so the suggested TAP to use is 6 or 7. As > far away as possible from the change point. My understanding was different here as of the following hw manual statement: "As the width of the input data is 1 (UI), select TAP6 or TAP7 which is *the median* of next TAP3 from TAP3" I understand from this that the median value should be considered here. > >> at the time of tuning, >> data is captured by the previous and next TAPs and the result is stored in >> the SMPCMP register (previous TAP in bits 22..16, next TAP in bits 7..0). >> If there is a mismatch b/w the previous and the next TAPs, it indicates >> that there is a change point of the input data. > > This is correct. > >> To comply with this, the code checks if this mismatch is present and >> updates the priv->smpcmp mask. > > That means you select the "change point" instead of avoiding it? > >> This change has been checked on the devices with the following DTSes by >> doing 50 consecutive reboots and checking for the tuning failure message: > > Okay, you might not have a failure message, but you might have selected > the worst TAP. Or? > >> + if (cmpngu_data != cmpngd_data) >> + set_bit(i, priv->smpcmp); > > Really looks like you select the change point instead of avoiding it. Looking again at it and digesting what you said about the tuning here, yes it seems I did it this way. > > However, with some SD cards, I also see the EIO error you see. So, there > might be room to improve TAP selection when all TAPs are good. I need to > check if this is really is the same case for the SD cards in question. Maybe better would be to change this condition: if (cmpngu_data != cmpngd_data) set_bit(i, priv->smpcmp); like this: if (cmpngu_data == cmpngd_data) set_bit(i, priv->smpcmp); ? I need to check it, though. Thanks for your input, Claudiu Beznea > > Happy hacking, > > Wolfram >
