On 12/2/22 16:00, Miquel Raynal wrote:
Hi Marek,
Hi,
marex@xxxxxxx wrote on Fri, 2 Dec 2022 15:31:40 +0100:
On 12/2/22 15:05, Miquel Raynal wrote:
Hi Francesco,
Hi,
[...]
I still strongly disagree with the initial proposal but what I think we
can do is:
1. To prevent future breakages:
Fix fdt_fixup_mtdparts() in u-boot. This way newer U-Boot + any
kernel should work.
2. To help tracking down situations like that:
Keep the warning in ofpart.c but continue to fail.
3. To fix the current situation:
Immediately revert commit (and prevent it from being backported):
753395ea1e45 ("ARM: dts: imx7: Fix NAND controller size-cells")
This way your own boot flow is fixed in the short term.
Here I disagree, the fix is correct and I think we shouldn't
proliferate incorrect DTs which don't match the binding document.
I agree we should not proliferate incorrect DTs, so let's use a modern
description then
Yes please !
, with a controller and a child node which defines the
chip.
But what if there is no chip connected to the controller node ?
If I understand the proposal here right (please correct me if I'm
wrong), then:
1) This is the original, old, wrong binding:
&gpmi {
#size-cells = <1>;
...
partition@N { ... };
};
2) This is the newer, but still wrong binding:
&gpmi {
#size-cells = <0>;
...
partitions {
partition@N { ... };
};
};
3) This is the newest binding, what we want:
&gpmi {
#size-cells = <0>;
...
nand-chip {
partitions {
partition@N { ... };
};
};
};
But if there is no physical nand chip connected to the controller, would
we end up with empty nand-chip node in DT, like this?
&gpmi {
#size-cells = <X>;
...
nand-chip { /* empty */ };
};
What would be the gpmi controller size cells (X) in that case, still 0,
right ? So how does that help solve this problem, wouldn't U-Boot still
populate the partitions directly under the gpmi node or into partitions
sub-node ?
Rather, if a bootloader generates incorrect (new) DT entries, I
believe the driver should implement a fixup and warn user about this.
PC does that as well with broken ACPI tables as far as I can tell.
I'm not convinced making a DT non-compliant with bindings again,
I am sorry to say so, but while warnings reported by the tools
should be fixed, it's not because the tool does not scream at you that
the description is valid. We are actively working on enhancing the
schema so that "all" improper descriptions get warnings (see the series
pointed earlier), but in no way this change makes the node compliant
with modern bindings.
I'm not saying the fix is wrong, but let's be pragmatic, it currently
leads to boot failures.
I fully agree that we do have a problem, and that it trickled into
stable makes it even worse. Maybe I don't fully understand the thing
with nand-chip proposal, see my question above, esp. the last part.
only to work around a problem induced by bootloader, is the right approach
here.
When a patch breaks a board and there is no straight fix, you revert
it, then you think harder. That's what I am saying. This is a temporary
solution.
Isn't this patch the straight fix, at least until the bootloader can be
updated to generate the nand-chip node correctly ?
This would be setting a dangerous example, where anyone could request a DT fix to be reverted because their random bootloader does the wrong thing and with valid DT clean up, something broke.
Please, you know this is not valid DT clean up. We've been decoupling
controller and chip description since 2016. What I am proposing is a
valid DT cleanup, not to the latest standard, but way closer than the
current solution.
I think I really need one more explanation of the nand-chip part above.
[...]
