Re: [RFC PATCH v2 1/5] mtd: cfi_cmdset_0002: Add support for polling status register
From: Joakim Tjernlund
Date: Thu Mar 21 2019 - 14:11:09 EST
On Thu, 2019-03-21 at 23:15 +0530, Vignesh Raghavendra wrote:
> HyperFlash devices are compliant with CFI AMD/Fujitsu Extended Command
> Set(0x0002) for flash operations, therefore drivers/mtd/chips/cfi_cmdset_0002.c
> can be use as is. But these devices do not support DQ polling method of
> determining chip ready/good status. These flashes provide Status
> Register whose bits can be polled to know status of flash operation.
> Cypress HyperFlash datasheet here, talks about CFI Amd/Fujitsu
> Extended Query version 1.5. Bit 0 of "Software Features supported" field
> of CFI Primary Vendor-Specific Extended Query table indicates
> presence/absence of status register and Bit 1 indicates whether or not
> DQ polling is supported. Using these bits, its possible to determine
> whether flash supports DQ polling or need to use Status Register.
> Add support for polling status register to know device ready/status of
> erase/write operations when DQ polling is not supported.
Isn't this new Status scheme just a copy of Intels(cmdset_0001)?
If so I think the new status impl. in 0002 should borrow from 0001 as this is a
hardened and battle tested impl.
I know other modern 0002 chips supports both old and new impl. of Status and I world
guess that we will see more chips with new Status only.