On Thursday 15 December 2016 00:52:24 Russell King - ARM Linux wrote:
> On Wed, Dec 14, 2016 at 10:12:43PM +0100, Pali Rohár wrote:
> > Commit 008a2ebcd677 ("ARM: dts: omap3: Remove skeleton.dtsi usage")
> > broke support for setting cmdline on Nokia N900 via
> > CONFIG_CMDLINE.
> >
> > It is because arm code booted in DT mode parse cmdline only via
> > function early_init_dt_scan_chosen() and that function does not
> > fill variable boot_command_line when DTB does not contain /chosen
> > entry. It is called from function early_init_dt_scan_nodes() in
> > setup_machine_fdt().
> >
> > This patch fixes it by explicitly filling boot_command_line in
> > function setup_machine_fdt() after calling
> > early_init_dt_scan_nodes() in case boot_command_line still remains
> > empty.
>
> This looks like a hack.
>
> First, the matter of the ATAGs compatibility. The decompressor
> relies on there being a pre-existing /chosen node to insert the
> command line and other parameters into. If we've dropped it (by
> dropping skeleton.dtsi) then we've just regressed more than just
> N900 - the decompressor won't be able to merge the ATAGs into the
> concatenated FDT.Hm... I did not think about it. But right this can be broken too... > Second, CONFIG_CMDLINE has never been in place on DT systems - it's > something atags_parse.c has been dealing with which isn't involved on > DT. For DT, we expect the command line to be passed in. If cmdline is not in DT, but /chosen exists, then function early_init_dt_scan_chosen() use cmdline from CONFIG_CMDLINE. > Now, given that, I find your commit message rather fishy. You seem > to be claiming that CONFIG_CMDLINE used to work, but the fact is, > we've never had it working on device tree systems. Looks like that CONFIG_CMDLINE really did not worked (correctly) on DT booted systems... We have already discussed about it on #armlinux > Instead, what I think was going on is that the bug you're seeing is > that the removal of skeleton.dtsi results in the /chosen node being > absent, which in turn prevents the decompressor picking the various > parameters out of the ATAGs and dropping them into the DT blob. In my case, bootloader did not provided any cmdline in ATAG, so decompressor did not parsed any cmdline... > That, to me, sounds like a regression, and the fix is not to hack > support for an unrelated feature, but to fix the original problem - > and I think in this case, it's reasonable to ask for the offending > commit to be reverted. I will let decision to others, who created and accepted that patch 008a2ebcd677. What I need is working CONFIG_CMDLINE as I had it before as bootloader for Nokia N900 does not pass any cmdline -- and without it I cannot boot userspace. But still, I would like to see working CONFIG_CMDLINE support for DT systems. Other systems (e.g. arm ATAG based or x86) have it. What is reason that CONFIG_CMDLINE is not supported for DT? -- Pali Rohár [email protected]
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