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Date:   Tue, 16 Oct 2018 10:09:22 +0200
From:   Stanislaw Gruszka <sgruszka@redhat.com>
To:     Tom Psyborg <pozega.tomislav@gmail.com>
Cc:     linux-wireless@vger.kernel.org,
        Daniel Golle <daniel@makrotopia.org>,
        Mathias Kresin <dev@kresin.me>, Felix Fietkau <nbd@nbd.name>
Subject: Re: [PATCH v4 4/8] rt2800: fix registers init for MT7620
Message-ID: <20181016080922.GB4158@redhat.com>
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On Fri, Oct 12, 2018 at 02:41:41PM +0200, Tom Psyborg wrote:
> On 12/10/2018, Stanislaw Gruszka <sgruszka@redhat.com> wrote:
> > On Fri, Oct 12, 2018 at 02:20:07PM +0200, Tom Psyborg wrote:
> >> > On upstream tree where this patch is intended
> >> > additional registers where never programmed as proper branch
> >> > were never used, because of additional check in RT5390 branch.
> >> >
> >>
> >> on my hardware additional registers were programmed in regardless of
> >> redundant check. that why i opened whole thread on forum since i
> >> couldn't understand how's that happening
> >
> > I don't understand how that possible either.
> 
> i'd assume because device use external lna

I have no idea how this could be related. But I think I found
somewhat reasonable explenation where the problem is.
I think below code :

	if (a || b || c) {
		CODE1();
	} else if (c) {
		CODE2();
	}

can not be deterministic and can be compiled differently depending
on compiler version and used options. Sometimes it could result
in this 

	if (a || b || c) {
		CODE1();
	}

and sometimes in this:

	if (a || b) {
		CODE1();
	} else if (c) {
		CODE2();
	}

So that would explain the problems you see. And indeed patch
could cause regression on systems where second variant of
initalizing RT6352 registers was used.

Thanks
Stanislaw