Binary SPI write-then-read doesn't confirm when there's nothing to read #158
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mikebdp2
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Feb 11, 2024
Based on the original work of @mpasternacki at BusPirate#158 - I have reviewed this commit and believe it is OK. Co-authored-by: Maciej Pasternacki <[email protected]> Signed-off-by: Mike Banon <[email protected]>
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In binary SPI mode, the write-then-read command is supposed to send a confirmation byte (
0x01) when the operation is complete. This happens inspi_read_to_uart, which is called only whenread > 0.When there is 0 bytes to read, BusPirate doesn't send any confirmation (and application needs to guess how long it needs to sleep to use SPI again without interfering).
Flashrom uses write-then-read without read to send commands (e.g. erase, program page). It waits for confirmation byte, which never arrives, so flashrom hangs.
This patch fixes the problem. I tested that the confirmation byte is sent and that flashrom no longer hangs.