Re: [PATCH] Revert "mtd: spinand: esmt: fix id code for F50D1G41LB"

[Md Sadre Alam]

Hi,

On 12/8/2025 2:56 PM, George Moussalem wrote:
> On 12/8/25 12:33, Miquel Raynal wrote:
> > On 02/12/2025 at 23:05:56 +08, Ziyang Huang <hzyitc@xxxxxxxxxxx> wrote:
> >
> > > This reverts commit dd26402642a0899fde59ea6b0852fad3d799b4cc.
> > >
> > > The issue George met is due to the limit of QPIC, not the issue of the
> > > flash chip.
> > >
> > > QPIC only supports 4 bytes ID. So the fifth byte is always 0.
> > >
> > > If we use spi-gpio, the fifth byte can be read correctly.
> > >
> > > Signed-off-by: Ziyang Huang <hzyitc@xxxxxxxxxxx>
> > > ---
> >
> > So how do we solve that?
> >
> > Is there anything than can be done on the qpic side?
>
> Hi Alam,
>
> Is the hardware itself limited to reading 4 ID bytes only or is it a
> driver limitation?

The hardware itself is limited to returning 4 ID bytes. QPIC reads the 
device ID and places it into the QPIC_NAND_FLASH_READ_ID register, which 
is 32‑bit wide. As a result, only 4 bytes of the device ID are available 
to software. The register stores the ID bytes in the order [31:24] = 
byte 3, [23:16] = byte 2, [15:8] = byte 1, [7:0] = byte 0.

Thanks,
Alam.