Message-ID: <20130325170432.GE20693@game.jcrosoft.org>
Date:	Mon, 25 Mar 2013 18:04:32 +0100
From:	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
To:	Douglas Gilbert <dgilbert@...erlog.com>
Cc:	Nicolas Ferre <nicolas.ferre@...el.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Ludovic Desroches <ludovic.desroches@...el.com>,
	tanzilli@...esystems.it, Robert.Nelson@...ikey.com
Subject: Re: [PATCH] ARM: at91: add Acme Systems Aria G25 board

On 11:23 Mon 25 Mar     , Douglas Gilbert wrote:
> On 13-03-25 10:31 AM, Jean-Christophe PLAGNIOL-VILLARD wrote:
> >On 09:48 Mon 25 Mar     , Douglas Gilbert wrote:
> >>On 13-03-25 08:22 AM, Jean-Christophe PLAGNIOL-VILLARD wrote:
> >>>On 09:49 Mon 25 Mar     , Nicolas Ferre wrote:
> >>>>From: Douglas Gilbert <dgilbert@...erlog.com>
> >>>>
> >>>>Signed-off-by: Douglas Gilbert <dgilbert@...erlog.com>
> >>>>Signed-off-by: Nicolas Ferre <nicolas.ferre@...el.com>
> >>>>---
> >>>>  arch/arm/boot/dts/ariag25.dts | 168 ++++++++++++++++++++++++++++++++++++++++++
> >>>>  1 file changed, 168 insertions(+)
> >>>>  create mode 100644 arch/arm/boot/dts/ariag25.dts
> >>>>
> >>>>diff --git a/arch/arm/boot/dts/ariag25.dts b/arch/arm/boot/dts/ariag25.dts
> >>>>new file mode 100644
> >>>>index 0000000..d18ef50
> >>>>--- /dev/null
> >>>>+++ b/arch/arm/boot/dts/ariag25.dts
> >>>>@@ -0,0 +1,168 @@
> >>>>+/*
> >>>>+ * ariag25.dts - Device Tree file for Acme Systems Aria G25 (AT91SAM9G25 based)
> >>>>+ *
> >>>>+ * Copyright (C) 2013 Douglas Gilbert <dgilbert@...erlog.com>,
> >>>>+ *                    Robert Nelson <robertcnelson@...il.com>
> >>>>+ *
> >>>>+ * Licensed under GPLv2 or later.
> >>>>+ */
> >>>>+/dts-v1/;
> >>>>+/include/ "at91sam9g25.dtsi"
> >>>>+
> >>>>+/ {
> >>>>+	model = "Acme Systems Aria G25";
> >>>>+	compatible = "acme,ariag25", "atmel,at91sam9g25ek", "atmel,at91sam9x5ek",
> >>>>+		     "atmel,at91sam9x5", "atmel,at91sam9";
> >>>I doube the code is compatible with the 9g25ek
> >>>
> >>>specially when you do not include it
> >>>>+
> >>>>+	aliases {
> >>>>+		serial4 = &usart3;
> >>>>+		serial5 = &uart0;
> >>>>+	};
> >>>you need to specify all
> >>>>+
> >>>>+	chosen {
> >>>>+		bootargs = "console=ttyS0,115200 root=/dev/mmcblk0p2 rw rootwait";
> >>>>+	};
> >>>>+
> >>>>+	memory {
> >>>>+		/* 128 MB, change this for 256 MB revision */
> >>>>+		reg = <0x20000000 0x8000000>;
> >>>>+	};
> >>>>+
> >>>>+	clocks {
> >>>>+		#address-cells = <1>;
> >>>>+		#size-cells = <1>;
> >>>>+		ranges;
> >>>>+
> >>>>+		main_clock: clock@0 {
> >>>>+			compatible = "atmel,osc", "fixed-clock";
> >>>>+			clock-frequency = <12000000>;
> >>>>+		};
> >>>>+	};
> >>>>+
> >>>>+	ahb {
> >>>>+		apb {
> >>>>+			mmc0: mmc@...08000 {
> >>>>+				/* N.B. Aria has no SD card detect (CD), assumed present */
> >>>>+
> >>>>+				pinctrl-0 = <
> >>>>+					&pinctrl_mmc0_slot0_clk_cmd_dat0
> >>>>+					&pinctrl_mmc0_slot0_dat1_3>;
> >>>>+				status = "okay";
> >>>>+				slot@0 {
> >>>>+					reg = <0>;
> >>>>+					bus-width = <4>;
> >>>>+				};
> >>>>+			};
> >>>>+
> >>>>+			i2c0: i2c@...10000 {
> >>>>+				status = "okay";
> >>>>+			};
> >>>>+
> >>>>+			i2c1: i2c@...14000 {
> >>>>+				status = "okay";
> >>>>+			};
> >>>>+
> >>>>+			/* TWD2+TCLK2 hidden behind ethernet, so no i2c2 */
> >>>>+
> >>>>+			usart0: serial@...1c000 {
> >>>>+				pinctrl-0 = <&pinctrl_usart0
> >>>>+					     &pinctrl_usart0_rts
> >>>>+					     &pinctrl_usart0_cts>;
> >>>>+				status = "okay";
> >>>>+			};
> >>>>+
> >>>>+			usart1: serial@...20000 {
> >>>>+				pinctrl-0 = <&pinctrl_usart1
> >>>>+					     /* &pinctrl_usart1_rts */
> >>>>+					     /* &pinctrl_usart1_cts */
> >>>>+					    >;
> >>>>+				status = "okay";
> >>>>+			};
> >>>>+
> >>>>+			usart2: serial@...24000 {
> >>>>+				/* cannot activate RTS2+CTS2, clash with
> >>>>+				 * ethernet on PB0 and PB1 */
> >>>>+				pinctrl-0 = <&pinctrl_usart2>;
> >>>>+				status = "okay";
> >>>>+			};
> >>>>+
> >>>>+			usart3: serial@...28000 {
> >>>>+				compatible = "atmel,at91sam9260-usart";
> >>>>+				reg = <0xf8028000 0x200>;
> >>>>+				interrupts = <8 4 5>;
> >>>>+				pinctrl-names = "default";
> >>>>+				pinctrl-0 = <&pinctrl_usart3
> >>>>+					     /* &pinctrl_usart3_rts */
> >>>>+					     /* &pinctrl_usart3_cts */
> >>>>+					    >;
> >>>>+				status = "okay";
> >>>>+			};
> >>>>+
> >>>>+			macb0: ethernet@...2c000 {
> >>>>+				phy-mode = "rmii";
> >>>>+				/* following can be overwritten by uboot 'ftd set' command */
> >>>>+				local-mac-address = [00 04 25 dd 10 01];
> >>>drop this, this is board specific
> >>>>+				status = "okay";
> >>
> >>Also the local-mac-address line is needed since it is edited
> >>by u-boot via this line:
> >>
> >>mod_dtb=fdt addr 0x27FF0000 ; fdt set ${eth0_dt_path}
> >>local-mac-address [ ${my_ethaddr} ]
> >>
> >>Interesting technique that: editing the dtb from u-boot prior to the
> >>Linux kernel using it ...
> >>
> >>So the u-boot environment file actually sets the MAC address. The Aria
> >>G25 has no NAND, flash or switches for setting a quasi unique MAC
> >>address. There seems to be no way to pass the MAC address on the
> >>kernel boot line (there was in the past). That leaves the microSD card
> >>and IMO u-boot is the best place to set that MAC address. My guess
> >>is that the Aria G25 is not the only board that has this "setting the
> >>MAC address" challenge.
> >>
> >>Finally of course that line is "board specific", that is why the
> >>file is called ariag25.dts :-)
> >The mac address is board (hw) uniq so no default in the dts, if none present
> >the kernel will generate one (private class).
> 
> Since when have MAC addresses been hw uniq? 
since EVER this is why you can resolve the IP <=> MAC on public network
That's why when you buy a mac address range, you need to prouve how you handle
it to buy a second range.

> My guess is
> a huge majority of MAC addresses are set in firmware.
> Since many embedded systems with wired ethernet face
> this problem, is it the job of Linux to make this more
> difficult than it already is?
yes but NEVER set the same mac address for every board (hw) in a DT or in C
> 
> >If the mac is specifued in the register the kernel re-use it.
> 
> Unless u-boot (or whatever) edits the dtb file before the
> Linux kernel sees it.
> 
> >This is the job of the booloader to set one. The dts in the kernel will be
> >used for every Aria not one board in particular
> 
> It is the job of someone to set it. A MAC address can be
> compiled into u-boot but that is about as useful as
> compiling it into Linux kernel.
no default one in the kernel dt

on some server we flash a dtb with a mac inside but this handle at production
level and the dts in the kernel does not have ANY default mac address
> 
> >if you keep the mac addres in the dts NACK
> 
> Seems strange to object to setting
>   local-mac-address = [00 00 00 00 00 00];
> when if the kernel sees that line it will do exactly the
> same thing as without that line? But the advantage of that
> line is that it gives the u-boot environment file the
> ability to edit the ariag25.dtb before the kernel sees it.
> And if the u-boot environment file is properly configured
> by the board manufacturer, then a quasi uniq, stable MAC
> address is generated.
in you patch you put a mac address not 00 00 00 00 00 00
and if u-boot is not able to add a property fix it

> 
> For more information about this technique see:
>   http://www.petalogix.com/support/kb/mac_addr_update
I known how dt work and how to handle it at bootloader level
for more than 6 years

Best Regards,
J.
> 
> 
> Doug Gilbert
> 
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