Re: [PATCH 1/2] ARM: dts: imx6q: extend support for the cm-fx6

Hi Christopher,

On 05/26/2016 02:37 PM, Igor Grinberg wrote:

On 05/26/2016 12:50 PM, Lucas Stach wrote:

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Hi Igor,

Am Donnerstag, den 26.05.2016, 11:50 +0300 schrieb Igor Grinberg:

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Hi Lucas,

Thanks for reviewing the patch(es).

On 05/23/2016 12:03 PM, Lucas Stach wrote:

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Am Montag, den 23.05.2016, 00:47 +0200 schrieb
christopher.spinrath-vA1bhqPz9FBZXbeN9DUtxg@public.gmane.org:

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From: Christopher Spinrath <redacted>

[...]

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+&ecspi1 {
+	fsl,spi-num-chipselects = <2>;
+	cs-gpios = <&gpio2 30 0>, <&gpio3 19 0>;
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_ecspi1>;
+	status = "okay";
+
+	flash: m25p80@0 {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		compatible = "st,m25p", "jedec,spi-nor";
+		spi-max-frequency = <20000000>;
+		reg = <0>;
+
+		partition@0 {
+			label = "uboot";
+			reg = <0x0 0xc0000>;
+		};
+
+		partition@c0000 {
+			label = "uboot environment";
+			reg = <0xc0000 0x40000>;
+		};
+
+		partition@100000 {
+			label = "reserved";
+			reg = <0x100000 0x100000>;
+		};

Partition layouts don't belong in the upstream DT, as it a device
configuration thing. Please kep them in the bootloader/firmware and make
this one pass the partition layout to the kernel.

I don't completely agree with this.
We have lots of partition layouts in the upstream DT.

No, we don't. At least not for the i.MX6. There are some for the earlier
i.MX boards, but IMO it's wrong to put device configuration into the
upstream DT. Let's not start doing this again.

Why not?
For i.MX6 there are 2 boards that have the partitioning scheme.
I'm not considering this a device configuration, but rather
a default partitioning layout/scheme.
Current case is for the firmware storage device that is not likely
to change.
Moreover, a DT is not really a part of the kernel, but lays along the kernel
sources for convenience and simplicity (at least IIRC as it was decided
about 5 years ago). It is more a part of the firmware for a device, than
an upstream kernel source code.
I think it is only a meter of time when Linus will decide that he does not
want it inside the kernel anymore...

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Moreover, this is the default layout and changing it, will
result in incompatibilities and also might result in device "bricking".
Those can be changed from the boot loader in case you need those
the other way around.
Another question of mine is, why should you?

Partition layout is device configuration, which is governed by the
device firmware.

Yet again, DT is a part of device firmware.
Moreover, the firmware (in that case U-Boot), can be configured
using the very same DT code, so not having this in, might force
various w/a and hacks.

quoted

By not having the partition layout in the upstream DT
people are forced to set it from the firmware, which is exactly the
right thing to do, weather or not you plan to change it at any time.

I might be ignorant, sorry for that.
Why? Why is it right and why would you want to force people to do that?

No answer?
I think it is worth keeping this as a default firmware layout.


-- 
Regards,
Igor.
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