On Tue, May 11, 2021 at 09:48:38AM -0500, Adam Ford wrote: > On Tue, May 11, 2021 at 7:20 AM Robin Gong <yibin.gong@xxxxxxx> wrote: > > > > 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. > > What I am seeing is that at times, the HCI UART loading before the DMA > firmware is loaded. > > [ 10.582037] Bluetooth: HCI UART driver ver 2.3 > [ 10.586867] Bluetooth: HCI UART protocol H4 registered > [ 10.593566] imx-sdma 30bd0000.dma-controller: sdma firmware not ready! > [ 10.594548] Bluetooth: HCI UART protocol Broadcom registered > [ 10.600108] imx-uart 30860000.serial: We cannot prepare for the RX slave dma! > > When I get the above message, the bluetooth chip I have throws > timeouts and does not function. > > [ 10.615090] imx-sdma 302c0000.dma-controller: loaded firmware 4.5 > > Once the firmware is loaded, I can unload the HCI Uart driver and > re-load Bluetooth works again. > > Based on that, I've been having my system delay the loading of the > Bluetooth modules until after the firmware is loaded, but this tells > me there is a relationship between the DMA and UART. Yeah, I can see how DMA firmware impacts your Bluetooth device, but do not follow how this spba node change make a difference here. Nevertheless, patches look good. Applied, thanks. Shawn
