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

On Wed, 2014-10-08 at 18:21 +0200, leroy christophe wrote:

Le 07/10/2014 02:15, Scott Wood a écrit :

quoted

On Sat, 2014-10-04 at 14:02 +0200, christophe leroy wrote:

quoted

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