linux-kernel - Re: [PATCH v2 2/3] ARM: dts: socfpga: fpga bridges bindings docs

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Message-ID: <20141024070042.GL10262@pengutronix.de>
Date:	Fri, 24 Oct 2014 09:00:42 +0200
From:	Steffen Trumtrar <s.trumtrar@...gutronix.de>
To:	atull@...nsource.altera.com
Cc:	jgunthorpe@...idianresearch.com, hpa@...or.com, monstr@...str.eu,
	michal.simek@...inx.com, rdunlap@...radead.org,
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	dinguyen@...nsource.altera.com, yvanderv@...nsource.altera.com
Subject: Re: [PATCH v2 2/3] ARM: dts: socfpga: fpga bridges bindings docs

Hi!

On Thu, Oct 23, 2014 at 06:51:06PM -0500, atull@...nsource.altera.com wrote:
> From: Alan Tull <atull@...nsource.altera.com>

(...)

> diff --git a/Documentation/devicetree/bindings/fpga/altera-hps2fpga-bridge.txt b/Documentation/devicetree/bindings/fpga/altera-hps2fpga-bridge.txt
> new file mode 100644
> index 0000000..bc24a2e
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/fpga/altera-hps2fpga-bridge.txt
> @@ -0,0 +1,53 @@
> +Altera FPGA/HPS Bridge Driver
> +
> +This driver manages a bridge between a FPGA and a host processor system (HPS).
> +User space can enable or disable the bridge by writing a "1" or a "0",
> +respectively, to its enable file under bridge's entry in
> +/sys/class/fpga-bridge.  Typically, one disables the bridges before
> +reprogramming the FPGA.  Once the FPGA is reprogrammed, the bridges are
> +reenabled.
> +

NAK.

This is all linux specific and doesn't belong here.

> +Required properties:
> +
> + - compatible     : should contain one of:
> +                     "altr,socfpga-hps2fpga-bridge"
> +                     "altr,socfpga-lwhps2fpga-bridge"
> +                     "altr,socfpga-fpga2hps-bridge"
> +
> + - clocks         : clocks used by this module
> +
> + - altr,l3-syscon : phandle of the l3 interconnect module
> +

L3 shouldn't be a syscon. Have you tried dumping the regmap in the debugfs if L3
is a syscon? Doesn't work.

> +Optional properties:
> + - label          : name that you want this bridge to show up as under
> +                    /sys/class/fpga-bridge.  Default is br<device#> if this is
> +                    not specified.
> +

Why? Linux-specific.

> + - init-val       : 0 if driver should disable bridge at startup
> +                    1 if driver should enable bridge at startup
> +                    driver leaves bridge in current state if property not
> +                    specified.
> +

Configuration in the DT? Really?

> +Example:
> +	hps_fpgabridge0: fpgabridge@0 {
> +		compatible = "altr,socfpga-hps2fpga-bridge";
> +		label = "hps2fpga";
> +		altr,l3-syscon = <&l3regs>;
> +		clocks = <&l4_main_clk>;
> +		init-val = <1>;
> +	};
> +
> +	hps_fpgabridge1: fpgabridge@1 {
> +		compatible = "altr,socfpga-lwhps2fpga-bridge";
> +		label = "lwhps2fpga";
> +		altr,l3-syscon = <&l3regs>;
> +		clocks = <&l4_main_clk>;
> +		init-val = <0>;
> +	};
> +
> +	hps_fpgabridge2: fpgabridge@2 {
> +		compatible = "altr,socfpga-fpga2hps-bridge";
> +		label = "fpga2hps";
> +		altr,l3-syscon = <&l3regs>;
> +		clocks = <&l4_main_clk>;
> +	};

The bridges are the buses into the FPGA. This has to be accomodated.
The bridges have two specified memory ranges: one the address space
of the bus, the second the register space for configuration.

This binding does NOT correctly describe the hardware. Sorry.

Regards,
Steffen

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