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

[Robin Gong <yibin.gong@nxp.com>]

On 5/11/21 22:49 Adam Ford <aford173@gmail.com> wrote:

> > 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!
Seems you apply my patch set ' add ecspi ERR009165 for i.mx6/7 soc family'
https://www.spinics.net/lists/linux-spi/msg26728.html 
where 'sdma firmware not ready' added?

> [   10.594548] Bluetooth: HCI UART protocol Broadcom registered
> [   10.600108] imx-uart 30860000.serial: We cannot prepare for the RX slave
> dma!
Why not use ROM script for UART as mailine linux-next did (even the above patch set)?
If so, I don't think you could such issue on your board. What script(peripheral types) you
set in uart dts such as below is 4-- MCU domain UART-> IMX_DMATYPE_UART->app_2_mcu:
 
dmas = <&sdma1 22 4 0>, <&sdma1 23 4 0>;

> 
> 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. 
If you use ram script, of course you should use it after firmware loaded. Actually 
Spba bus in dts is only used for per_2_per script judging if the peripheral address
could be accessed directly by SDMA over SPBA, if yes, set SDMA_WATERMARK_LEVEL_SP
to let per_2_per script access peripheral over SPBA, otherwise, access peripheral by
AIPS instead like ARM side did. Please check with below commit for more.
Besides, per_2_per script is used for audio data sample rate convert between ASRC and
various audio input. So audio peripherals include ASRC should be in register scope of 
'spba-bus' . But with your patch, there are two 'spba-bus' device node in dts, so the first
Spba-bus should contain audio peripheral, otherwise, 'of_find_compatible_node
(NULL, NULL, "fsl,spba-bus")' may find the wrong one so that SDMA_WATERMARK_LEVEL_SP
Never be set.

BTW, do you mean the above firmware load issue you met is gone if this patch applied?
If yes, that really surprised me...

commit 8391ecf465ec5c8ccef547267df6d40beb8999a4
Author: Shengjiu Wang <shengjiu.wang@freescale.com>
Date:   Fri Jul 10 17:08:16 2015 +0800

    dmaengine: imx-sdma: Add device to device support