QSPIFBlockDevice: status register write size cannot have a fixed value

[cy-vaira]

Description

In _sfdp_set_quad_enabled(), sr_write_size is fixed to QSPI_MAX_STATUS_REGISTER_SIZE (0x03). I found this causing issue while porting QSPI for CY8CPROTO_062_4343W to work with the NOR flash S25FL512S. For this flash chip, the write size for the status register must be 2. Otherwise, enabling quad mode fails.

Reference: S25FL512S datasheet, Section: 9.3.7 Write Registers (WRR 01h). The following line makes it clear that write size must be 2.

CS# must be driven to the logic high state after the eighth or sixteenth bit of data has been latched. If not, the Write Registers (WRR) command is not executed.

Issue request type

[ ] Question
[X] Enhancement
[ ] Bug

[ciarmcom]

Internal Jira reference: https://jira.arm.com/browse/MBOCUSTRIA-1028

[offirko]

sr_write_size does not have a fixed size. It is initialized to QSPI_MAX_STATUS_REGISTER_SIZE but can change according to QER bit.

Actually, QSPI_MAX_STATUS_REGISTER_SIZE was 2 and I changed it to 3 in the commit below..because turning fast_mode on other boards required writing status_reg+config_reg together (3 bytes total).
Some flash chips require setting both status&config registers together (3bytes) and the SFDP specification doesn't give a way to identify it..

9b3bca8#diff-8e2c0034f3ea6c90e7ecf6baef0fe7c5

I'll fix the code to separate status register size between 'set_quad_enable' and 'fast_mode_enable'

[offirko]

Handled by: #10171

[cy-vaira]

@offirko is there a plan to support 4-bytes addressing anytime soon?

[offirko]

@VairaRamasamy : we have considered adding support for 4-bytes addressing once we see demand for SPI Flash devices with larger capacity.
Do you require 4-bytes addressing for flash larger than 16MB?

[cy-vaira]

Yes. We need it. Cypress' flash chips used on PSoC 6 kits support up to 64 MB.

[offirko]

@VairaRamasamy - thanks for the information. We can try to make it into 5.13
I've added in CC the relevant people for planning.

CC: @dannybenor , @ARMmbed/mbed-os-maintainers