Hi Jerome, On Mon, Apr 29, 2019 at 8:50 PM Jerome Brunet <jbrunet@xxxxxxxxxxxx> wrote: > > On Mon, 2019-04-29 at 20:31 +0200, Martin Blumenstingl wrote: > > Hi Jerome, > > > > On Mon, Apr 29, 2019 at 10:29 AM Jerome Brunet <jbrunet@xxxxxxxxxxxx> wrote: > > > On Sat, 2019-04-27 at 22:02 +0200, Martin Blumenstingl wrote: > > > > Hi Jerome, > > > > > > > > On Tue, Apr 23, 2019 at 11:03 AM Jerome Brunet <jbrunet@xxxxxxxxxxxx> wrote: > > > > > At the moment, all our attempts to enable HS400 on Amlogic chipsets have > > > > > been unsuccessful or unreliable. Until we can figure out how to enable this > > > > > mode safely and reliably, let's force it off. > > > > last year I have seen issues with HS400 on my Khadas VIM2: [0] > > > > have you tested all other patches from this series and HS400 is still > > > > not working for you? > > > > > > Because HS400 was never really stable to begin with. > > > It was a mistake to enable it on the VIM2 > > > > > > > I'm curious because this patch is early in the series and all the > > > > tuning fixes and improvements are after this patch. > > > > > > There are several reasons why this new tuning won't solve the HS400 problem: > > > - Signal resampling tuning granularity gets worse when rate rises. The resampling > > > is done using the input frequency. We can basically resample up to the value of > > > internal divider. > > > > > > In HS200 - Fin is 1GHz, Fout is 200MHz (1/5) so the resample range is [0, 4] > > > In HS400 - Fin should be fdiv5 (400MHZ) and in such case, no resampling is > > > possible (internal div = 1) > > > Even if we keep 1GHz, then out is 333MHz max giving a range of [0, 2] > > > that's not enough to tune > > this limitation would be great to have in the description of patch 7 > > from this series > > That's not really a limitation. I should probably not have mentioned as it it seems to > have made things even more unclear. I disabled HS400 before introducing the new tuning on > purpose. Any comment regarding hs400 does not belong in patch 7 IHMO. If you want > to add comment regarding hs400, I think it belongs here > > > > > > Going further, tuning the Rx path does not make much sense in HS400 since we > > > should be using the data strobe signal to account for the round trip delay of > > > the clock and correctly sample Rx. AFAICT, If there is a tuning to be done for > > > HS400, it is most likely linked to the data strobe. > > it would be great to have a better description as part of the commit > > message - with that you can add my: > > Acked-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx> > > > > my proposal for an update patch description (apologies I have > > incorrectly summarized your findings): > > " > > At the moment, all our attempts to enable HS400 on Amlogic chipsets have > > been unsuccessful or unreliable: > > - signal resampling without delay adjustments and phase tuning for the > > RX and TX clocks (this caused CRC errors and hangs even without HS400 > > mode, for example on the Khadas VIM, Khadas VIM2 and libretech-cc > > boards) > > - signal resampling without delay adjustments and RX clock phase > > tuning (some HS200 and HS400 eMMC chips were not recognized, for > > example on the Khadas VIM and Khadas VIM2 boards) > > - signal resampling tuning with delay adjustments only (works fine for > > HS200 and UHS modes but doesn't fix HS400 eMMC chips, for example on > > Khadas VIM2) > > > > Further improvements for the HS400 mode are likely to be linked to the > > data strobe signal. > > Until we can figure out how to enable this mode safely and reliably, > > let's force it off. > > " > > Thanks for effort but all this just maintain the blur around HS400 on amlogic. > > Let me rephrase it: > Tuning (phase or resampling) is meant to compensate the clock round trip in UHS > and HS200 modes. In HS400, this should be taken care of by the data strobe. > But we have not been to enable this reliably enable this on amlogic chipset ... I wasn't aware of this: so far I assumed that we're not setting the phase correctly, end of the story. thank you again for taking your time to explain this! > ... and I believe we are back to the original commit message. no need to update the description just to explain how HS400 works in general, so feel free to use my: Acked-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx> Martin
