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

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

On 5/14/21 Adam Ford <aford173@gmail.com> wrote:  
> I did this on the 5.13-rc1 which appears to have this series applied.

Sorry, I didn't see it on 5.13-rc2 even....

> > 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>;
> 
> I didn't change the DMA references from the default, and I didn't check to
> verify whether they are right or not.
If so, I don't think you could see the above firmware load error since UART
use ROM firmware by default instead.

> 
> >
> > >
> > > 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.
> 
> I don't pretend to understand the details of the dma driver, but I attempted to
> make the patch match the address range of both spba busses from the
> technical reference manual,so there should be an spba bus for the audio
> peripherals and an spba bus for the serial peripherals like UART and SPI.  I
> only named them spba1 and spba2 based on the memory ranges defined in
> the ref manual. Table 2-5 shows
> SBPA1 is 3080_0000 and table 2-3 shows SPBA2 starts at 3000_0000 which is
> what I believe I did in this patch.
Okay, I'm not saying your patch is not wrong, just curious about your UART issue
you mentioned :)


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