On Tue, Aug 19, 2014 at 2:47 PM, Stephen Warren [off-list ref] wrote:

On 08/18/2014 06:11 PM, Andrew Bresticker wrote:

quoted

On Mon, Aug 18, 2014 at 4:43 PM, Stephen Warren [off-list ref]
wrote:

quoted

On 08/18/2014 05:24 PM, Andrew Bresticker wrote:

quoted

On Mon, Aug 18, 2014 at 9:10 AM, Stephen Warren [off-list ref]
wrote:

quoted

On 08/16/2014 09:20 AM, Andreas F?rber wrote:

quoted

Hi,

Am 13.08.2014 21:14, schrieb Dylan Reid:

quoted

The Acer Chromebook 13, codenamed Big, contains an NVIDIA tegra124
processor and is similar to the Venice2 reference platform.

The keyboard, USB 2, audio, HDMI, sdcard, and emmc have been tested
and work on the 1266x768 models.  The HD models haven't yet been
tested.

WiFi does not work yet, it needs at least some PMIC changes to enable
the 32k clock.

The elan trackpad is not yet functional but hopefully will be soon as
there are patches under review.

There is also an issue on reboot because the TPM isn't reset.  It
will
cause the stock firmware to enter recovery mode.  This can be worked
around by an EC-reset, press the refresh and power keys at the same
time.

quoted

quoted

diff --git a/arch/arm/boot/dts/tegra124-nyan-big.dts

b/arch/arm/boot/dts/tegra124-nyan-big.dts
new file mode 100644
index 0000000..79f1852

--- /dev/null
+++ b/arch/arm/boot/dts/tegra124-nyan-big.dts

@@ -0,0 +1,1136 @@
+/dts-v1/;
+
+#include <dt-bindings/input/input.h>
+#include "tegra124.dtsi"
+
+/ {
+       model = "Acer Chromebook 13";
+       compatible = "google,nyan-big", "nvidia,tegra124";

In light of v1 and the above commit message referring to this as
Google
Big, shouldn't this be "google,big", "nvidia,tegra124" and optionally
"google,nyan" as secondary string, independent of the new file name?

Despite this board having been derived from Nyan, it isn't Nyan, so I
don't
think Nyan should be part of any compatible value, nor a separate
compatible
value.

"google,nyan-big" is the compatible string that the bootloader on
these devices looks for.  It's also the convention we are now using
for our ARM devices, as Olof has already mentioned.

I don't understand "that the bootloader looks for"; why is the bootloader
doing anything w.r.t the compatible value in the DT that's passed to the
kernel.

The ChromeOS bootloader ("depthcharge") boots FIT images and selects
the appropriate device-tree from the image based on the compatible
string.  On Big boards, it looks for "google,nyan-big".  This only
becomes an issue if there are multiple device-trees in the FIT image.
If there's only a single configuration (or you chain-load U-Boot),
then the bootloader will boot with that configuration.  If you build a
kernel image in the ChromiumOS environment, however, you'll end up
with multiple device-trees (all those built by the kernel config at
least) in the FIT image - this is what allows us to boot the same
binary on different boards.

This just makes me dislike FIT (and DT ABIs) even more, although I suppose
the same issue would arise if the DTBs were stored in separate files and
looked up by filename.

Yes, or stored in separate files and looked up by compatible field.

Do you have a suggestion on a better way to solve it, btw? Definitely
not one of those things we can fix retroactively, but if it works
poorly for you upstream we'll consider improvements if we can for
future products.

I'm not a huge fan of fitImage myself, but it gets the work done.

I have to say this sucks, because it means that a downstream bootloader is
imposing an ABI on the mainline kernel without a chance to fix things during
upstreaming. For all other boards, we've concentrated on mainline U-Boot as
the bootloader precisely so that strange behaviour of our downstream product
kernels don't force the hand of the mainline kernel design.

Still, I suppose I have no choice but to drop my objection here.

Thanks for being pragmatic on this one, Stephen!


-Olof