Re: [PATCH 2/3] mtd: spi-nor: use rdid-dummy-ncycles DT property

[Tudor Ambarus]

Hi, Rob,

On 3/19/25 11:30 PM, Rob Herring wrote:
> On Wed, Mar 19, 2025 at 06:47:44PM +0900, Takahiro Kuwano wrote:
>> There are infineon flashes [1] that require 8 dummy cycles for the
>> 1-1-1 Read ID command. Since the command is not covered by JESD216
>> or any other standard, get the number of dummy cycles from DT and use
>> them to correctly identify the flash.
> 
> If Read ID fails, then couldn't you just retry with dummy cycles? Or 

I think Read ID won't fail when the op requires 8 dummy cycles, it
probably just reads garbage on the first 8 cycles, so we risk to wrongly
match other flash IDs.

> would unconditionally adding dummy cycles adversely affect other chips?

Adding 8 dummy cycles to chips that don't need it, would mean ignoring
the first byte of the flash ID, thus we again risk to wrongly match
against other flash IDs.

> 
> Otherwise, add a specific compatible to imply this requirement. Adding 
> quirk properties doesn't scale.

Do you mean a flash name compatible, like "cyrs17b512,spi-nor"? The
problem that I see with that is that we no longer bind against the
generic jedec,spi-nor compatible, so people need to update their DT in
case they use/plug-in a different flash on their board.

Thanks,
ta