Re: [PATCH 2/2] mtd: rawnand: Add timings for Kioxia TH58NVG2S3HBAI4

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Rickard,

Rickard X Andersson <Rickard.Andersson@axis.com> wrote on Wed, 20 May
2020 14:16:57 +0000:

> > > I have created a new patchset that I will send shortly. This patchset does however not use onfi_find_equivalent_sdr_mode(..), that could be a future improvment. My patchset falls back to mode 0 if the specialized timings does not work for the controller.  
> >
> > Thanks for updating!
> >
> > Actually I wrote it because of a previous discussion with Boris who
> > told me that this mode field would be badly understood and he actually
> > got it right as in your previous submission this field was set to 0
> > while, IIRC, you told me it was close to mode 3. This is important to
> > controllers that cannot tweak the parameters but just pick an ONFI
> > mode. So the timings they choose must fit the slowest mins and fastest
> > maxs of your new set of timings. Hence the use of the helper which
> > seems needed. It is actually pretty straightforward so I don't
> > understand your choice of not making use of it?
> >
> > As this is the primary contribution of this type, I would like to get
> > it right so that other contributors can refer to it :)  
> 
> If I understand you correctly you want me to use onfi_find_equivalent_sdr_mode in order to find the corresponding onfi mode. Then you want me to use onfi_fill_data_interface and loop towards mode 0 checking which mode the controller accepts? I just thought it was a "messy" to duplicate this code in all vendor drivers.
> Or do you mean that I should just use onfi_find_equivalent_sdr_mode to set ."timings.mode" and let nand_base to do the looping in case error is returned from th58nvg2s3hbai4_choose_data_interface (i.e specialized timings not accepted by the controller).

Sorry for the misunderstanding. What I think you should try is:
1/ call onfi_find_equivalent_sdr_mode() to set the timings.mode field.
2/ call nand_controller_supports_data_interface()
3/ if the controller supports the timings, set
chip->default_timing_mode accordingly and return 0.
4/ if the controller does not support the timings, you may want to
propose other standard timings to test by setting
chip->default_timing_mode anyway but returning an error which means
"best interface has not been found yet" so the rest of the
choose_data_interface() helper will try the remaining ONFI modes
automatically (fallbacks to 0 anyway).

Thanks,
Miquèl

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