Re: [PATCH v2 1/2] spi: fsl-spi: Fix parameter ram offset setup for CPM1

From: Scott Wood
Date: Wed Oct 08 2014 - 12:30:45 EST


On Wed, 2014-10-08 at 18:21 +0200, leroy christophe wrote:
> Le 07/10/2014 02:15, Scott Wood a Ãcrit :
> > On Sat, 2014-10-04 at 14:02 +0200, christophe leroy wrote:
> >> What should it look like if that offset had to be in the device tree ?
> > If the offset is not relocatable or discoverable, it should stay in the
> > device tree. If you have an old chip you wouldn't have
> > fsl,cpm1-spi-reloc and thus you'd still have "0x3d80 0x30" in reg.
> This index is from the start of the dual port RAM. It is 0x2000 above
> the start of the CPM area.
> In the DTS, we have:
>
> soc@ff000000 {
> compatible = "fsl,mpc885", "fsl,pq1-soc";
> #address-cells = <1>;
> #size-cells = <1>;
> device_type = "soc";
> ranges = <0x0 0xff000000 0x28000>;
> bus-frequency = <0>;
> clock-frequency = <0>;
>
> cpm@9c0 {
> #address-cells = <1>;
> #size-cells = <1>;
> compatible = "fsl,mpc885-cpm", "fsl,cpm1";
> ranges;
> reg = <0x9c0 0x40>;
> brg-frequency = <0>;
> interrupts = <0>; // cpm error interrupt
> interrupt-parent = <&CPM_PIC>;
>
> muram@2000 {
> #address-cells = <1>;
> #size-cells = <1>;
> ranges = <0x0 0x2000 0x2000>;
>
> data@0 {
> compatible = "fsl,cpm-muram-data";
> reg = <0x0 0x1c00>;
> };
> };
>
> spi: spi@a80 {
> #address-cells = <1>;
> #size-cells = <0>;
> cell-index = <0>;
> compatible = "fsl,spi", "fsl,cpm1-spi";
> reg = <0xa80 0x30 0x3d80 0x30>;
> interrupts = <5>;
> interrupt-parent = <&CPM_PIC>;
> mode = "cpu";
>
>
> The binding allows me to do an of_iomap() on the parameter RAM, hence to
> get access to the relocation index which is inside it.
> But if the relocation index is 0, I have to calculate it by myself
> because the calling function expects it in return.
> The binding is also supposed to tell that the muram is at 0xff002000.
> But I don't know how I can get this info and use it to calculate the
> index of my param RAM ? I need to calculate the index which is 1d80
> (0x3d80 - 0x2000)

What binding are you talking about? There is no published binding for
this yet.

As for what the driver should do, it should do an of_iomap(), but what
it does with the resulting memory depends on the compatible. For
fsl,cpm1-spi, the result would be the parameter RAM for the device. For
fsl,cpm1-spi-reloc and fsl,cpm2-spi, it would be the relocation
register. The driver would either read the contents of the register, or
write a different offset.

My understanding is that the relocation register would only be zero on
the chips where we'd use fsl,cpm1-spi, not fsl,cpm1-spi-reloc.

-Scott


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