linux-kernel - Re: [PATCH v2] clk:mxs: Fix bug on frequency divider

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Message-ID: <20150924121738.GP3529@tiger>
Date:	Thu, 24 Sep 2015 05:17:38 -0700
From:	Shawn Guo <shawnguo@...nel.org>
To:	Stefan Wahren <stefan.wahren@...e.com>
Cc:	Victorien Vedrine <victorien.vedrine@...rys.net>,
	linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
	sboyd@...eaurora.org, mturquette@...libre.com,
	shawn.guo@...aro.org,
	"Fabio.Estevam@...escale.com" <Fabio.Estevam@...escale.com>,
	Marek Vasut <marex@...x.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2] clk:mxs: Fix bug on frequency divider

On Fri, Sep 18, 2015 at 09:21:17AM +0200, Stefan Wahren wrote:
> +Shawn's new address
> +linux-arm-kernel
> 
> > On drivers/clk/mxs/clk-frac.c, the function clk_frac_round_rate returned a bad
> > result. The division before multiplication computes a wrong value ; the
> > calculation is inverted to fix the problem. The second issue is that the exact
> > rate have decimals and they are truncate. The consequence is that the function
> > clk_frac_set_rate (which use the result of clk_frac_round_rate) computes a
> > wrong value for the register (the rate generated can be closer to the desired
> > rate). The correction is : if there is decimal to the result, it is rounded to
> > the next larger integer.
> > On drivers/clk/mxs/clk-frac.c, the function clk_frac_recalc_rate returned
> > a bad result. The multiplication is made before the division to compute a
> > correct value.
> >
> > Signed-off-by: Victorien Vedrine <victorien.vedrine@...rys.net>

Acked-by: Shawn Guo <shawnguo@...nel.org>
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