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Adds a driver for the external QSPI PSRAM hanging off QMI chip select 1, such as the 8 MiB APS6404 fitted on the Pimoroni Pico Plus 2. rp23xx_psramconfig() assigns the CS1 pin, reads the device ID over the QMI direct interface to confirm an APS6404-family part (KGD 0x5D), resets it into quad mode and programs the QMI M1 timing/read/write formats so the region at 0x11000000 becomes directly addressable and writable. Because driving the QMI in direct mode stalls execute-in-place from the flash, the detection and (re)configuration code runs from RAM (.time_critical) with interrupts disabled; the command bytes are selected with immediates rather than a .rodata table for the same reason. The register values follow the Raspberry Pi Pico SDK setup_psram(). The detection routine only keeps the QMI DIRECT_CSR synchronization that is strictly necessary. Each candidate busy-wait was removed one at a time and re-verified on hardware: the post-enable "cooldown" waits, the READ_ID TXEMPTY wait (redundant with the BUSY wait after it), and a fixed nop delay proved unnecessary and are omitted. The three BUSY waits that remain -- after the quad-mode nudge, after each READ_ID byte, and after each reset/quad-enable command -- are required and carry a comment explaining that the frame must finish shifting before the chip select is deasserted, and what breaks otherwise (garbage ID reads, or the shared QMI bus wedging). rp23xx_psram_restore() re-applies the M1 configuration and is meant to be called from the flash write path, which goes through the bootrom and reconfigures the shared QMI for chip select 0. rp23xx_heaps.c is wired into the build and now uses the detected size, so the PSRAM is exposed to the memory manager (added to the main heap, used as a separate heap, or as the user heap) and is skipped cleanly when no PSRAM is present. Enabled by default on the pimoroni-pico-2-plus:nsh configuration, where it adds the 8 MiB to the main heap. A documentation page for the Pimoroni Pico Plus 2 is added alongside the other rp23xx boards, covering its serial console, LED, the external PSRAM and how it is exposed to the heap, the supported capabilities and the available configurations, with a photo of the board. Tested on Pimoroni Pico Plus 2 hardware: detection reports the 8 MiB APS6404, the region is read/write across its whole range (ramtest word, half-word and byte passes, marching/pattern/address-in-address), and the heap reports the extra 8 MiB. Assisted-by: Claude Code:claude-opus-4-8 Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com> |
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| applications | ||
| components | ||
| contributing | ||
| debugging | ||
| faq | ||
| guides | ||
| implementation | ||
| introduction | ||
| logos | ||
| platforms | ||
| quickstart | ||
| reference | ||
| ReleaseNotes | ||
| standards | ||
| testing | ||
| .gitignore | ||
| conf.py | ||
| glossary.rst | ||
| index.rst | ||
| known-warnings.txt | ||
| legacy_README.md | ||
| make.bat | ||
| Makefile | ||
| Pipfile | ||
| Pipfile.lock | ||
| security.rst | ||
| substitutions.rst | ||