Re: [PATCH v4 2/2] spi: rockchip: skip the unused FIFO direction on a one-wire device

[Quentin Schulz <quentin.schulz@cherry.de>]

Hi Cole,

On 8/21/26 1:55 PM, Cole Munz wrote:
> The controller has a transfer-mode field that can run transmit-only or
> receive-only instead of both, which leaves the unused FIFO out of the
> transfer entirely. The driver never used it for that: claim_bus always
> programmed TMOD_TR, and the only other mode came from an opportunistic
> switch to TMOD_RO for read-only transfers.
> 
> A device described with spi-{tx,rx}-bus-width = <0> has no wire in that
> direction at all, so now that the width reaches plat->mode as
> SPI_NO_TX/SPI_NO_RX, pick the transfer mode from it. A write-only
> display stops clocking receive bytes nobody reads.
> 
> The transmit-only case needs one more change. The 8-bit loop paces
> itself on the receive FIFO and sets toread unconditionally, so with no
> receive path it would wait on a FIFO that stays empty forever. Leave
> toread at zero there and let the existing wait_till_not_busy() at the
> end of the chunk handle completion, which is the same thing that
> already covers a transmit component today.
> 
> The restore at the end of a read-only transfer went back to a hardcoded
> TMOD_TR, which would undo the device's own mode. Restore what the mode
> asks for instead.
> 
> Signed-off-by: Cole Munz <Munzzyy1@proton.me>
> Tested-by: Alexey Charkov <alchark@flipper.net>

Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>

I'm planning to take both patches for 2027.01 (next branch; end of next 
week) as this is not fixing a recent regression or a security issue.

Thanks!
Quentin