[PATCH v4 1/6] mtd: spi-nor: Add manufacturer read id function

[liao jaime]

Hi Michael


>
> Hi,
>
> Am 2023-10-13 10:23, schrieb liao jaime:
> >> >> > After checking with Macronix designer, a-a-b-b-c-c is the data
> >> >> > arrangement for
> >> >> > read id operation of flash in 8D-8D-8D.
> >> >>
> >> >> Could you please point to any specification? I doubt there is one
> >> >> and every vendor will do it slightly differently. I mean we already
> >> >> have some flashes which (apparently) reply to RDID in 8d8d8d.
> >> >>
> >> >> For example, see the Semper flash datasheet:
> >> >> https://www.infineon.com/dgdl/Infineon-S28HS256T_S28HS512T_S28HS01GT_S28HL256T_S28HL512T_S28HL01GT_256-Mb_(32-MB)_512-Mb_(64-MB)_1-Gb_(128-MB)_HS-T_(1.8-V)_HL-T_(3.0-V)_Semper_Flash_with_Octal_Interface-DataSheet-v03_00-EN.pdf?fileId=8ac78c8c7d0d8da4017d0ee6bca96f97&da=t
> >> >>
> >> >> Have a look at Table 78 (or search for RDIDN_4_0) and Figure 28.
> >> > For Figure 28 in this datasheet, I think it means that data latch
> >> > while DS raising and falling edge.
> >> > The data arrangement of read id follow the 9.2(Manufacturer and Device
> >> > ID).
> >> > As below are the data arrangement for vendors.
> >> > For Infineon, a-b-c-d-e-f
> >> > For Micron, a-b-c-d-e-f
> >> > For Macronix, a-a-b-b-c-c
> >>
> >> So there is no standard among vendors, infineon as well as micron is
> >> using 8d8d8d and macronix is using 8d8d8s. And - please correct me if
> > Macronix read id operation is not 8d8d8s, it just look like 8d8d8s on
> > datasheet
> > but flash send 2 bytes data per DQS cycle exactly.
>
> Two DQS edges, yes.
>
> > I think whether to use 8d or 8s depends on how many times data is
> > latched
> > within per cycle.
>
> I see and I agree with you. The flash behaves like it's in 8d8d8d mode,
> but
> just send every byte of the id twice. Well, then I'd argue, it's a quirk
> of
> your flash.
I cannot refute that.

>
> So Tudor and Pratyush want to hide that away in macronix.c. I would like
> to
> see this handled in the core, because all flashes do the very same after
> switching to octal mode and that is trying to do a rdid and see whether
> they got a sane response. And during cleanup I noticed that this code is
> pretty much copy and paste among all these flashes and looks very
> open-coded.
>
> But to move forward here, keep it in macronix.c.
Do you mean that I can keep v3 method as below for comparing ID after enable
8D-8D-8D mode?

for (i = 0; i < nor->info->id_len; i++)
if (buf[i * 2] != nor->info->id[i])
return -EINVAL;

>
> >> I'm wrong - the data strobe signal is optional.
> > As I know, data strobe signal is needed when 8D-8D-8D mode.
> > Infineon data strobe signal called "DS".
> > Macronix and Micron data strobe signal called "DQS"
>
> Maybe Pratyush can help here. But as far as I know, the data strobe
> is optional. E.g. on a layerscape ls1028 you can use an internal dummy
> strobe if it's not connected. The timing is then determined by pad
> delays.
It would be great if Pratyush could provide additional information.

>
> -michael

Thanks
Jaime