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

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Message-ID: <3985193.nXz0F4qod7@avalon>
Date:	Fri, 20 Nov 2015 16:50:06 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
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 Geert,

On Friday 20 November 2015 10:07:31 Geert Uytterhoeven wrote:
> On Fri, Nov 20, 2015 at 9:58 AM, Laurent Pinchart 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).

That's indeed simpler. Could you capture the behaviour in a source code 
comment ?

-- 
Regards,

Laurent Pinchart

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