On Thu Mar 20, 2025 at 12:30 AM CET, 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 > would unconditionally adding dummy cycles adversely affect other chips? Yes exactly. IIUC, the first byte of the auto discovery (RDID command) would return random data, because the output driver of the flash is disabled. The second byte would then return the manufacturer id and third and fourth the device id. This makes auto discovery fundamentally broken with this chip as the first byte might randomly match any manufacturer within our database. Takahiro, if you can reach designer of this chip, you might tell them, that this was not the greatest idea :o > Otherwise, add a specific compatible to imply this requirement. Adding > quirk properties doesn't scale. Since auto discovery doesn't work at all, you might just add, "infineon,cyrs17b512" *instead of* "jedec,spi-nor" (because it doesn't support the usual RDID command"). Alternatively, we could introduce a "generic" compatible which just uses the standard RDSFDP command instead of RDID for discovery. Rob? Then we'd need some SFDP fingerprinting mechanism to match the SFDP to a particular flash type. -michael
