linux-kernel - Re: [PATCH v2 2/2] clk: mediatek: Add MT8173 MMPLL change rate support

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Date:	Fri, 10 Jul 2015 13:46:37 +0800
From:	James Liao <jamesjj.liao@...iatek.com>
To:	Stephen Boyd <sboyd@...eaurora.org>
CC:	Matthias Brugger <matthias.bgg@...il.com>,
	Mike Turquette <mturquette@...libre.com>,
	Heiko Stubner <heiko@...ech.de>, <devicetree@...r.kernel.org>,
	<srv_heupstream@...iatek.com>, <linux-kernel@...r.kernel.org>,
	Ricky Liang <jcliang@...omium.org>,
	"Rob Herring" <robh+dt@...nel.org>,
	<linux-mediatek@...ts.infradead.org>,
	"Sascha Hauer" <kernel@...gutronix.de>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 2/2] clk: mediatek: Add MT8173 MMPLL change rate
 support

Hi Stephen,

On Wed, 2015-07-08 at 17:46 -0700, Stephen Boyd wrote:
> On 07/08/2015 01:37 AM, James Liao wrote:
> > diff --git a/drivers/clk/mediatek/clk-pll.c b/drivers/clk/mediatek/clk-pll.c
> > index 68af518..622e7b6 100644
> > --- a/drivers/clk/mediatek/clk-pll.c
> > +++ b/drivers/clk/mediatek/clk-pll.c
> > @@ -138,16 +138,28 @@ static void mtk_pll_calc_values(struct mtk_clk_pll *pll, u32 *pcw, u32 *postdiv,
> >  		u32 freq, u32 fin)
> >  {
> >  	unsigned long fmin = 1000 * MHZ;
> > +	const struct mtk_pll_div_table *div_table = pll->data->div_table;
> >  	u64 _pcw;
> >  	u32 val;
> >  
> >  	if (freq > pll->data->fmax)
> >  		freq = pll->data->fmax;
> >  
> > -	for (val = 0; val < 4; val++) {
> > +	if (div_table) {
> > +		if (freq > div_table[0].freq)
> > +			freq = div_table[0].freq;
> > +
> > +		for (val = 0; div_table[val + 1].freq != 0; val++) {
> > +			if (freq > div_table[val + 1].freq)
> > +				break;
> > +		}
> >  		*postdiv = 1 << val;
> > -		if (freq * *postdiv >= fmin)
> > -			break;
> > +	} else {
> > +		for (val = 0; val < 5; val++) {
> > +			*postdiv = 1 << val;
> > +			if ((u64)freq * *postdiv >= fmin)
> >
> 
> No mention of this cast in the commit text. Is this fixing a bug? If so,
> please mention it and/or split this bug fix off of this patch.
> 

Yes, this is a fix to avoid u32 overflow. I'll split it in next patch.


Best regards,

James


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