RE: [PATCH 1/2] arm64: dts: imx8mn: Add spba1 bus

From: Robin Gong
Date: Tue May 11 2021 - 08:20:49 EST

On 2021/05/11 18:45 Adam Ford <aford173@xxxxxxxxx> wrote:
> > Also may I ask if you have a real use case for this bus node?
> The reference manual shows the SPBA bus tells the DMA controller which
> peripherals are associated with it. Nearly all the i.MX boards use this. The
> boards I support have Bluetooth devices connected to a UART running high
> speeds, and if the DMA driver isn't loaded, I can see a performance change.
Compare PIO with DMA on UART, but not w/o this 'spba bus node ' patch?

> In fact, if the DMA firmware isn't loaded, I often get transfer errors.
UART use SDMA ROM firmware instead of RAM firmware, so it should work
even without sdma RAM firmware loaded. Still curious what really happen in
your board without this patch.