On Tue, Jun 11, 2019 at 04:53:58PM +0200, Maxime Ripard wrote:
Hi!
On Tue, Jun 11, 2019 at 10:28:19AM -0400, Tom Rini wrote:
On Tue, Jun 11, 2019 at 11:37:28AM +0200, Maxime Ripard wrote:
On Mon, Jun 10, 2019 at 10:11:39AM +0100, Andre Przywara wrote:
On Mon, 10 Jun 2019 10:30:37 +0200 Maxime Ripard maxime.ripard@bootlin.com wrote:
Hi Maxime,
thanks for having a look!
On Sat, Jun 08, 2019 at 02:26:53AM +0100, Andre Przywara wrote:
At the moment we need to configure the place where U-Boot tries to load its environment from at compile time. This is not only inflexible, but also unnecessary, as we have easy access to the boot source.
This series prepares U-Boot on Allwinner boards to load the environment from the same media where the SPL and U-Boot proper were loaded from. This allows to keep one firmware binary, and copy it to an SD card, eMMC or even SPI flash, without needing to configure it differently.
This does change a couple of things though. The environment used to be loaded always from the same source, no matter the boot device. This means that if you would set an SD card, you would get the environment from the eMMC. Same thing for FEL. This is no longer the case.
I don't know whether it's a good or a bad thing, but it should be mentionned.
This is true, I failed to mention that.
To start a discussion on this: I consider the current (fixed location) behaviour somewhat surprising and limiting, and couldn't find a real use case where this would be required. Happy to hear of one! Instead I thought about those cases:
- There is some botched U-Boot plus environment on the eMMC. You want to
boot from SD card to have a clean start, possibly to fix it. But it will load the possibly outdated, broken or even unrelated environment from eMMC.
This one might be a feature though. Being able to restore / fix an environment in the eMMC running from an SD card has save me a couple of times. Or booting from the SD card because the U-Boot on the eMMC is broken, while the environment is working.
- You want to boot from SD card without touching the eMMC at all. Saving
the environment will spoil that.
But it goes against that one, which might be more important / sensible.
- You want to have one image for all possible boot media.
That won't happen, only because NAND is a thing.
Some of this is perhaps an argument for adding a sub-command to specify where the environment is to be read from. Heuristics are still only a best guess and won't get it right every time.
I was mostly talking about the distribution of the image itself. While eMMC, SD and SPI flash can be made to take the same image, NAND will require a particular ECC and randomizer setup that requires that it's bundled separately.
Right. But as you noted, there's use cases for boot from one to fix another.
And even then, I'm not really sure that it's a good thing. A U-Boot build these days is roughly in the same sizes than a stripped down Linux image. For an inferior solution in pretty much every aspect.
Hey now. We aren't _quite_ that large. And we are (really!) trying to find a happy medium between "distros want X/Y/Z for everyone" and "can we commonly get back to UNDER 512kB maybe? Please?".
I'm exagerating a little, but barely. A current build for the SoC Andre was mentionning takes 600kB. And since the trend has been for the binaries to grow for quite some time now, I'm pretty sure everyone will reserve 1MB just to be sure they have some room to spare.
Yes, it's larger than I would like, and features keep being added. But also, yes, DM stuff needs a harder look.
Now, getting a kernel image to fit in a MB takes a bit of time, but it's not really impossible to achieve. And if you can reclaim that MB dedicated to U-Boot, it's actually fairly easy to do.
I've tried to have the size reduced at some time because we were corrupting our U-Boot binary as soon as we where using saveenv (which is probably one of the worst issue we could have), and it ended up with everyone agreeing that we needed to reduce the size, just not the one they were using.
It's kind of weird that people haven't yet embraced defconfig as they are in Linux, where every distro has its own configuration, and it's perfectly fine.
To the last point, distributions seemingly very much want to avoid building U-Boot and there's a growing contingent that wishes the hardware shipped with the DTB for the hardware as well.