linux-kernel - Re: [PATCH v2 2/2] ARC: enable uboot support unconditionally

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Date:   Mon, 5 Aug 2019 13:17:02 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Alexey Brodkin <Alexey.Brodkin@...opsys.com>
Cc:     linux-stable <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Corentin Labbe <clabbe@...libre.com>,
        "khilman@...libre.com" <khilman@...libre.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>,
        Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
        Vineet Gupta <Vineet.Gupta1@...opsys.com>
Subject: Re: [PATCH v2 2/2] ARC: enable uboot support unconditionally

On Fri, Aug 02, 2019 at 04:25:39PM +0000, Alexey Brodkin wrote:
> Hi Greg,
> 
> > > May we have this one back-ported to linux-4.19.y?
> > >
> > > It was initially applied to Linus' tree during 5.0 development
> > > cycle [1] but was never back-ported.
> > >
> > > Now w/o that patch in KernelCI we see boot failure on ARC HSDK
> > > board [2] as opposed to normally working later kernel versions.
> > >
> > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=493a2f812446e92bcb1e69a77381b4d39808d730
> > > [2] https://storage.kernelci.org/stable/linux-4.19.y/v4.19.59/arc/hsdk_defconfig/gcc-8/lab-baylibre/boot-hsdk.txt
> > >
> > > Below is that same patch but rebased on linux-4.19 as in its pristine
> > > form it won't apply due to offset of one of hunks.
> > 
> > Why is this patch ok for stable kernel trees?  Are you not removing
> > existing support in 4.19 for a feature that people might be using there?
> > What bug is this fixing that requires this removal?
> 
> This patch removes a Kconfig option in a trade for properly working
> detection of arguments passed from U-Boot.
> 
> Back in the day [3] we had to add that option to get kernel reliably working
> in use-cases w/o U-Boot (those were typically loading kernel image via JTAG).
> But with a couple of fixes applied to linux-4.19.y already we no longer need
> that explicit toggle as we may rely on data passed via dedicated registers
> and thus automatically know if there was U-Boot which passed some info to
> the kernel or there was no U-Boot and we don't need to mess with garbage in
> those registers.
> 
> Main reason is to make vanilla 4.19.y kernels usable on HSDK board in KernelCI
> environment. Now they don't boot, see [2] as in HSDK's defconfig ARC_UBOOT_SUPPORT
> is not set. So we have 2 solutions:
> 
> 1. Add ARC_UBOOT_SUPPORT to arch/arc/configs/hsdk_defconfig
>    But we cannot do it for vanilla kernel because we simply cannot even submit that
>    change to the Linus' tree as that Kconfig option was removed.
>    Which means we cannot back-port it, right :)
> 
> 2. Back-port proposed patch which already exists in the Linus'tree and thus is
>    perfectly back-portable.
> 
> Makes sense?

Ok, it's your arch, you get to deal with the angry users if you have any
:)

now queued up.

greg k-h