Re: [PATCH] mtd: spi-nor: core: Introduce spi_nor_abort_octal_dtr()

[Pratyush Yadav <ptyadav@amazon.de>]

Hi,

On Wed, Dec 13 2023, liao jaime wrote:

> Hi Michael
>
>
>>
>> Hi,
>>
>> >> > Some flashes contains 8D_8D_8D information in SFDP but did not enter
>> >> > octal DTR mode if conditions are not satisfied.
>> >>
>> >> What exactly are these conditions? Rather than "abort" the octal mode,
>> >> the flash shouldn't have that capability in the first place.
>> > "Abort" is not a good word.
>> > Is it better for using "discard"?
>> > 3 conditions should be satisfied before enable octal dtr mode.
>> > 1. function hook in nor->params->set_octal_dtr
>> > 2. nor->read_proto and nor->write_proto are SNOR_PROTO_8_8_8_DTR
>> > 3. nor->flags & SNOR_F_IO_MODE_EN_VOLATILE
>> > Flash driver still bring 8D_8D_8D protocol instructions in 1s-1s-1s
>> > mode if
>> > conditions are not satisfied.
>> > In a case, flash ID didn't include in vendor's ID table.
>> > It will be "spi-nor-generic".
>> > 8D-8D-8D information could be parsed in SFDP but
>> > nor->params->set_octal_dtr
>> > didn't hook vendor specific function for enabling octal dtr mode.
>> > So that it still bring 8D protocol in 1s-1s-1s mode and have no chance
>> > to select 1-1-8 protocol.
>> > I think it may better to re-select a suitable protocol for this case.
>>
>> Just that we are on the same page. You are using the spi-nor-generic
>> driver, but that driver will elect the 8d8d8d protocol but that won't
>> work, because we don't have a .set_octal_dtr. Therefore, the fallback
>> is 1s1s1s. Correct?
> Yes.
> Based on my understanding, typically, flash that support the 1-1-8 feature
> also tends to support 8D-8D-8D feature.
> However, in the case of spi-nor-generic, we don't have a .set_octal_dtr.
> Therefore, I believe that if octal DTR mode cannot be enabled due to
> this, it might be necessary to reconsider and choose a suitable feature.

Can't you parse the SCCR to learn how to enable 8D-8D-8D mode for
generic flash drivers? That way you can set octal_enable() for generic
flashes as well.

To be clear, I still think you should implement Michael's suggestions
about masking out SNOR_HWCAPS_8_8_8. This is an enhancement that you can
add on top to enable Octal DTR for generic flashes via SFDP. You seem to
have a flash capable of doing that so might as well enable its full
powers.

[...]

-- 
Regards,
Pratyush Yadav



Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879




______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/