Re: [PATCH] usb: typec: fusb302: Send PD messages longer than one SMBus block

[sashiko-bot@kernel.org]

> The whole message, tokens included, goes to the FIFO in a single SMBus
> block write, which carries at most 32 bytes and silently drops the rest.
> A message with six or seven data objects needs up to 39, so it loses its
> closing tokens including TXON: the chip never sends it, the transmission
> times out, and the truncated bytes stay in the TX FIFO ahead of the next
> message. A Discover Identity ACK carrying a full set of sink-vdos is one
> such message, as is a Source_Capabilities with six or seven PDOs.
> 
> Write the message in chunks of at most one SMBus block. The FIFOS
> register has no address auto-increment and queues every byte written to
> it, so consecutive writes append to the 48-byte TX FIFO. TXON is the
> one token that is not queued but starts the transmitter as soon as it is
> written. It still comes last, so transmission begins only once the whole
> message is in the FIFO, as the datasheet recommends.
> 
> Flush the TX FIFO if a write fails, so that a partial message cannot
> stay queued and go out together with the next one as a garbled frame.
> 
> Signed-off-by: Alexey Charkov <alchark@flipper.net>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261102-fusb302-long-tx-v1-1-0d2719488c3b@flipper.net?part=1