Details:

The OSPI controller uses a DQS signal to sample data when the PHY Module is enabled. However, there is an issue in the module which requires that this sample must occur within a window defined by the internal clock. Read operations are subject to external delays, which change with temperature. In order to guarantee valid reads at any temperature, a special tuning algorithm must be implemented which selects the most robust TX, RX, and Read Delay values.

Workaround(s):

The workaround for this bug is described in detail in the application note spract2 (link: https://www.ti.com/lit/spract2). To sample data under some PVT conditions, it is necessary to increment the Read Delay field to shift the internal clock sampling window. This allows sampling of the data anywhere within the data eye. However, this has these side effects:

1. PHY Pipeline mode must be enabled for all read operations. Because PHY Pipeline mode must be disabled for writes, reads and writes must be handled separately.
2. Hardware polling of the busy bit is broken when the workaround is in place, so SW polling must be used instead. Writes must occur through DMA accesses, within page boundaries, to prevent interruption from either the host or the flash device. Software must poll the busy bit between page writes. Alternatively, writes can be performed in non-PHY mode with hardware polling enabled.
3. STIG reads must be padded with extra bytes, and the received data must be right-shifted.