ES0392 errata coverage review + AXI-SRAM (§2.2.10) presence guard

[twitzelbos]

Summary

A deliberate cross-reference of the STM32H750 device errata (ES0392 Rev 15) against this firmware and its Renode models, prompted by a "revisiting the RM and errata, anything we're missing?" review. Honest conclusion: nothing load-bearing is missing — the errata that touch our hot paths are already handled. This PR captures that review durably and adds one regression guard for the highest-value un-modellable workaround.

What's here

docs/errata-coverage.md — the full coverage table, in three buckets:

• Handled + verified: §2.2.10 (AXI SRAM read corruption → AXI_TARG7_FN_MOD poke, gated to pre-rev-V, mirrors libDaisy), §2.7.4 (QUADSPI internal-timing dance), §2.2.21 (480 MHz gated to rev V), §2.6.6/.7 (SDRAM timing side-stepped in sdram.rs).
• Not applicable (checked): §2.1.1 write-through cache (audited clean — only write-through region is read-only QSPI XIP; writable regions are non-cacheable or write-back), §2.7.6, §2.9.x ADC, §2.5.x DMAMUX, §2.2.17/.24, §2.2.3, §2.19.x.
• Latent traps (noted, no action): §2.1.5 (DMB-after-invalidate — design note for the in-progress DMA cache-coherency exerciser), §2.7.5 (last-FSIZE-byte read), §2.2.13 (USB DP/DM drive), rev-X-could-do-480.

renode/errata_workarounds.robot — §2.2.10 is the same silent-omission class as the SDNWE=PH5 pin bug and the FMC BCR1.FMCEN gate: a required register poke Renode can't model behaviourally. Guard it with a presence assertion (à la qspi_ncs_pinmux.robot): boot the real bootloader and assert AXI_TARG7_FN_MOD is written on pre-rev-V / rev-Y silicon and left untouched on rev V. A small AXI-interconnect ArrayMemory (0x5100_8000) in daisy_seed.repl makes the poke land observably.

Verification

• renode/errata_workarounds.robot — 3/3 green (two-sided: pre-V/rev-Y must write 1, rev-V must leave 0, proving the write is conditional).
• renode/clocks_boot.robot — still 3/3 green (the shared-platform neighbour; the added memory is additive).

No firmware behaviour changes — docs + one Renode model memory + one new test.

🤖 Generated with Claude Code