From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wolfgang Denk <wd@denx.de>
Date: Mon, 16 Jul 2018 14:42:48 +0200
Subject: [U-Boot] [PATCH] serial: ns16550: Add register shift variable
In-Reply-To: <1b0d33fa-adfb-9825-5ae8-8bded1678c0c@ltec.ch>
References: <1531492980-16543-1-git-send-email-fb@ltec.ch>
 <20180714104721.A8B69240175@gemini.denx.de>
 <20180714154933.GF2888@bill-the-cat>
 <1b0d33fa-adfb-9825-5ae8-8bded1678c0c@ltec.ch>
Message-ID: <20180716124248.1872E24015D@gemini.denx.de>
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Dear Felix,

In message <1b0d33fa-adfb-9825-5ae8-8bded1678c0c@ltec.ch> you wrote:
>
> >> This needs to be rewritten.
> > 
> > To try and help clarify, the property in question means "quantity to
> > shift the register offsets by."  It should be clear in our Kconfig help
> > entry as well that this is what we're looking for.
> > 
> Thanks for this! The help text will be fixed in v2.

None of the places I could find in the Linux
Documentation/devicetree/bindings directory actually explains what
"shift the register offsets" means.   Only the code reveals that
this means a LEFT shift of the register address (offset).

At least one place in Linux interprets <reg-shift> differently; here
it operates on the _data_ (instead there they use <reg-spacing>):

"devicetree/bindings/ipmi/ipmi-smic.txt":

- reg-shift - The amount to shift the registers to the right to get the data
        into bit zero.

(see ipmi_si_mem_io.c


So can we please add an explanation what _exactly_ this means?

Thanks.


Wolfgang Denk

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DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
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