RE: [PATCH v2 5/9] arm64: dts: ls1046a: make dma-coherent global to the SoC

[Leo Li]

> -----Original Message-----
> From: Sean Anderson <sean.anderson@xxxxxxxx>
> Sent: Friday, September 23, 2022 11:11 AM
> To: Leo Li <leoyang.li@xxxxxxx>; shawnguo@xxxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx
> Cc: robh+dt@xxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; Laurentiu Tudor <laurentiu.tudor@xxxxxxx>
> Subject: Re: [PATCH v2 5/9] arm64: dts: ls1046a: make dma-coherent global
> to the SoC
> 
> 
> Hi All,
> 
> On 9/15/22 7:34 PM, Li Yang wrote:
> > These SoCs are really completely dma coherent in their entirety so add
> > the dma-coherent property at the soc level in the device tree and drop
> > the instances where it's specifically added to a few select devices.
> >
> > Signed-off-by: Laurentiu Tudor <laurentiu.tudor@xxxxxxx>
> > Signed-off-by: Li Yang <leoyang.li@xxxxxxx>
> > ---
> >  arch/arm64/boot/dts/freescale/fsl-ls1046a.dtsi | 5 +----
> >  1 file changed, 1 insertion(+), 4 deletions(-)
> >
> > diff --git a/arch/arm64/boot/dts/freescale/fsl-ls1046a.dtsi
> > b/arch/arm64/boot/dts/freescale/fsl-ls1046a.dtsi
> > index 27033c558e3e..e406499a26b4 100644
> > --- a/arch/arm64/boot/dts/freescale/fsl-ls1046a.dtsi
> > +++ b/arch/arm64/boot/dts/freescale/fsl-ls1046a.dtsi
> > @@ -273,6 +273,7 @@ soc: soc {
> >  		#size-cells = <2>;
> >  		ranges;
> >  		dma-ranges = <0x0 0x0 0x0 0x0 0x10000 0x00000000>;
> > +		dma-coherent;
> >
> >  		ddr: memory-controller@1080000 {
> >  			compatible = "fsl,qoriq-memory-controller"; @@ -
> 355,7 +356,6 @@
> > crypto: crypto@1700000 {
> >  			ranges = <0x0 0x00 0x1700000 0x100000>;
> >  			reg = <0x00 0x1700000 0x0 0x100000>;
> >  			interrupts = <GIC_SPI 75 IRQ_TYPE_LEVEL_HIGH>;
> > -			dma-coherent;
> >
> >  			sec_jr0: jr@10000 {
> >  				compatible = "fsl,sec-v5.4-job-ring", @@ -
> 794,7 +794,6 @@ pcie1:
> > pcie@3400000 {
> >  			#address-cells = <3>;
> >  			#size-cells = <2>;
> >  			device_type = "pci";
> > -			dma-coherent;
> >  			num-viewport = <8>;
> >  			bus-range = <0x0 0xff>;
> >  			ranges = <0x81000000 0x0 0x00000000 0x40
> 0x00010000 0x0 0x00010000   /* downstream I/O */
> > @@ -834,7 +833,6 @@ pcie2: pcie@3500000 {
> >  			#address-cells = <3>;
> >  			#size-cells = <2>;
> >  			device_type = "pci";
> > -			dma-coherent;
> >  			num-viewport = <8>;
> >  			bus-range = <0x0 0xff>;
> >  			ranges = <0x81000000 0x0 0x00000000 0x48
> 0x00010000 0x0 0x00010000   /* downstream I/O */
> > @@ -874,7 +872,6 @@ pcie3: pcie@3600000 {
> >  			#address-cells = <3>;
> >  			#size-cells = <2>;
> >  			device_type = "pci";
> > -			dma-coherent;
> >  			num-viewport = <8>;
> >  			bus-range = <0x0 0xff>;
> >  			ranges = <0x81000000 0x0 0x00000000 0x50
> 0x00010000 0x0 0x00010000   /* downstream I/O */
> >
> 
> I'd like to summarize the conclusions of [1] below. This patch breaks I2C0,
> which is the only user of eDMA at the moment. eDMA is noncoherent
> because snooping is not enabled for it. I have submitted a patch [2] to U-
> Boot to enable snooping for eDMA. For now, this patch must add dma-
> noncoherent to the i2c0 node.

I have sent a V3 yesterday to set dma-noncoherent on edma node.  But are you saying that the dma-noncoherent need to be added to the i2c node to make it work?

For the u-boot patch, I will check with the hardware team to see if it is safe to set the reserved bit for edma snooping.  There is a problem with this is that it breaks the i2c for older u-boot.  Probably the best way is to make the default to be non-coherent in dts and update it in u-boot when snooping is enabled?

Regards,
Leo