Fix a bug in the Aspeed SPI driver to support full-duplex operations. - #603
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chander-nexthop wants to merge 1 commit into
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Fix a bug in the Aspeed SPI driver to support full-duplex operations.#603chander-nexthop wants to merge 1 commit into
chander-nexthop wants to merge 1 commit into
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tx_buf == rx_buf, and otherwise issued a separate post-transfer ioread8_rep burst that returns zeros. spidev always hands the driver distinct tx/rx bounce buffers, so userspace SPI_IOC_MESSAGE full-duplex reads (e.g. the FPGA register bridge) always read back zeros. Add patches-sonic/aspeed-spi-txrx-fix-full-duplex-capture.patch to capture RX during the TX loop whenever an rx buffer is present and restrict the separate read burst to pure reads, and register it in the series after aspeed-ast2700-support.patch. Behaviour is unchanged for write-only, read-only, and shared-buffer full-duplex (e.g. the TPM) transfers. Signed-off-by: Chandrasekaran Swaminathan <chander@nexthop.ai>
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The aspeed-txrx controller only latched MISO during its TX loop when tx_buf == rx_buf, and otherwise issued a separate post-transfer ioread8_rep burst that returns zeros. spidev always hands the driver distinct tx/rx bounce buffers, so userspace SPI_IOC_MESSAGE full-duplex reads (e.g. the FPGA register bridge) always read back zeros.
Add patches-sonic/aspeed-spi-txrx-fix-full-duplex-capture.patch to capture RX during the TX loop whenever an rx buffer is present and restrict the separate read burst to pure reads, and register it in the series after aspeed-ast2700-support.patch. Behaviour is unchanged for write-only, read-only, and shared-buffer full-duplex (e.g. the TPM) transfers.
We have given this patch to Aspeed too and they have agreed to take it in their repository in a future release. Till that happens we will need this patch.