[ot] hw/opentitan: spi_device: fix off-by-one last_read_addr #195
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AlexJones0
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Sep 24, 2025
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I don't know OpenTitan's SPI device well but this looks correct to me from the docs and code.
Some relevant links I found if it helps anyone else reviewing:
- Docs about update on CS de-assertion https://opentitan.org/book/hw/ip/spi_device/doc/registers.html#last_read_addr
- Relevant part of the read command where the address was incremented:
qemu/hw/opentitan/ot_spi_device.c
Line 1231 in 996a48e
- Also https://opentitan.org/book/hw/ip/spi_device/doc/theory_of_operation.html#buffer-management:
The LAST_READ_ADDR shows the last read address of the recent read command. For instance, if the host system issues 0xABCD_E000 and reads 128 (or 0x80) bytes, the LAST_READ_ADDR after the transaction will show 0xABCD_E07F. It does not show the commands falling into the mailbox region or Read SFDP command’s address
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Thanks for the links |
AlexJones0
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Sep 24, 2025
Read commands automatically increment the address so the last read address register was too high. I don't want to assign to this register before we do the increment because the OpenTitan docs say it's only updated on CS release. Signed-off-by: James Wainwright <james.wainwright@lowrisc.org>
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Signed-off-by: James Wainwright <james.wainwright@lowrisc.org>
AlexJones0
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Sep 24, 2025
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Read commands automatically increment the address so the last read address register was too high. We still need to do the register assignment on CS deassert to match the RTL (see Alex's comment below).
I tested this against the OpenTitan
spi_device_flash_smoketest.