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

[liao jaime]

Hi Michael

>
> Hi,
>
> >> > 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.
I think whether to use 8d or 8s depends on how many times data is latched
within per cycle.

> 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"

>
> -michael

Thanks
Jaime