Re: [PATCH 00/10] Raspberry Pi SPI speedups

[Stefan Wahren <wahrenst@xxxxxxx>]

Hi Lukas,

Am 03.08.19 um 12:10 schrieb Lukas Wunner:
> So far the BCM2835 SPI driver cannot cope with TX-only and RX-only
> transfers (rx_buf or tx_buf is NULL) when using DMA:  It relies on
> the SPI core to convert them to full-duplex transfers by allocating
> and DMA-mapping a dummy rx_buf or tx_buf.  This costs performance.
>
> Resolve by pre-allocating reusable DMA descriptors which cyclically
> clear the RX FIFO (for TX-only transfers) or zero-fill the TX FIFO
> (for RX-only transfers).  Patch [07/10] provides some numbers for
> the achieved latency improvement and CPU time reduction with an
> SPI Ethernet controller.  SPI displays should see a similar speedup.
> I've also made an effort to reduce peripheral and memory bus accesses.

i know the BCM2711 / Raspberry Pi 4 isn't upstreamed yet, but this
series hasn't been tested with RPi 4?

I only want to know.