[1/2] powerpc/85xx: add pixis indirect mode device tree node

The Freescale P1022 has a unique pin muxing "feature" where the DIU video
controller's video signals are muxed with 24 of the local bus address signals.
When the DIU is enabled, the bulk of the local bus is disabled, preventing
access to memory-mapped devices like NOR flash and the pixis FPGA.

In this situation, the pixis supports "indirect mode", which allows access
to the pixis itself by reading/writing addresses on specific local bus
chip selects.  CS0 is used to select which pixis register to access, and
CS1 is used to read/write the value.

To support this, we introduce another board-control child node of the
localbus node that contains a 'reg' property for CS0 and CS1.  This will
produce the correct physical addresses for CS0 and CS1.

Signed-off-by: Timur Tabi <timur@freescale.com>
---
 arch/powerpc/boot/dts/p1022ds.dts |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)

On Thu, Nov 17, 2011 at 12:57:38PM -0600, Timur Tabi wrote:
> The Freescale P1022 has a unique pin muxing "feature" where the DIU video
> controller's video signals are muxed with 24 of the local bus address signals.
> When the DIU is enabled, the bulk of the local bus is disabled, preventing
> access to memory-mapped devices like NOR flash and the pixis FPGA.
> 
> In this situation, the pixis supports "indirect mode", which allows access
> to the pixis itself by reading/writing addresses on specific local bus
> chip selects.  CS0 is used to select which pixis register to access, and
> CS1 is used to read/write the value.
> 
> To support this, we introduce another board-control child node of the
> localbus node that contains a 'reg' property for CS0 and CS1.  This will
> produce the correct physical addresses for CS0 and CS1.
> 
> Signed-off-by: Timur Tabi <timur@freescale.com>
> ---
>  arch/powerpc/boot/dts/p1022ds.dts |   14 ++++++++++++++
>  1 files changed, 14 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/powerpc/boot/dts/p1022ds.dts b/arch/powerpc/boot/dts/p1022ds.dts
> index 24a73e9..3e85d8c 100644
> --- a/arch/powerpc/boot/dts/p1022ds.dts
> +++ b/arch/powerpc/boot/dts/p1022ds.dts
> @@ -24,6 +24,20 @@
>  			  0x2 0x0 0xf 0xffa00000 0x00040000
>  			  0x3 0x0 0xf 0xffdf0000 0x00008000>;
>  
> +		/*
> +		 * This node is used to access the pixis via "indirect" mode,
> +		 * which is done by writing the pixis register index to chip
> +		 * select 0 and the value to/from chip select 1.  Indirect
> +		 * mode is the only way to access the pixis when DIU video
> +		 * is enabled.  Note that this assumes that the first column
> +		 * of the 'ranges' property above is the chip select number.
> +		 */
> +		board-control@0,0 {
> +			compatible = "fsl,p1022ds-indirect-pixis";
> +			reg = <0x0 0x0 1	/* CS0 */
> +			       0x1 0x0 1>;	/* CS1 */
> +		};
> +
>  		nor@0,0 {
>  			#address-cells = <1>;
>  			#size-cells = <1>;

U-Boot should mark some of these devices as disabled, based on whether
indirect mode is enabled on boot.  If you're not going to do that, at
least remove simple-bus from the compatible list.

Something like this is probably the best way to describe it:

localbus {
	compatible = "...", "fsl,elbc", "simple-bus";
	ranges = <...>;
	#address-cells = <2>;
	#size-cells = <2>;

	mux {
		compatible = "fsl,p1022ds-localbus-mux"; // no simple-bus
		fsl,localbus-mux-mode = "indirect"; // inital state on boot
		ranges;
		#address-cells = <2>;
		#size-cells = <2>;

		board-control@0,0 {
			compatible = "fsl,p1022ds-indirect-pixis";
			reg = <0 0 1
			       1 0 1>;
			fsl,localbus-mux-avail = "indirect";
		};

		flash@0,0 {
			...
			fsl,localbus-mux-avail = "direct";
		};

		...
	};
};

Or encode the mode as part of reg, as I suggested for someone else here:
http://lists.ozlabs.org/pipermail/devicetree-discuss/2011-November/009378.html

-Scott