linux-kernel - Re: [PATCH 00/25] serial: sh-sci: Add external clock and BRG Support

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Date:	Fri, 20 Nov 2015 10:07:31 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:	Geert Uytterhoeven <geert+renesas@...der.be>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Simon Horman <horms@...ge.net.au>,
	Magnus Damm <magnus.damm@...il.com>,
	Yoshinori Sato <ysato@...rs.sourceforge.jp>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	Linux-sh list <linux-sh@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 00/25] serial: sh-sci: Add external clock and BRG Support

Hi Laurent,

On Fri, Nov 20, 2015 at 9:58 AM, Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
> On Friday 20 November 2015 09:22:16 Geert Uytterhoeven wrote:
>> On Thu, Nov 19, 2015 at 10:08 PM, Laurent Pinchart wrote:
>> > Could you briefly explain (and even better in a source code comment) how
>> > you handle baud rate calculation with the chained BRGs ?
>>
>> I'll do that. Note that there's no chaining of BRGs, only muxing (so yes, it
>> needs more clarification ;-).
>
> Really ? I thought the BRG-EC was one possible input for the internal BRG ?
> Does it bypass the internal BRG ? Or do you configure the internal BRG to not
> divide the clock when using the BRG-EC ?

Yes, it's bypassed.

Cfr. SCSCR.CKE[1:0].
'00' means internal BRG (although the docs state P divided by 1/4/16/64),
'10' means SCK or SC_CLK (SCIF_CLK/INT_CLK).

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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