linux-kernel - RE: [PATCH] clk: samsung: Fix pll36xx_recalc

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Date:	Wed, 05 Jun 2013 20:51:29 +0900
From:	Kukjin Kim <kgene.kim@...sung.com>
To:	'Doug Anderson' <dianders@...omium.org>
Cc:	'Tomasz Figa' <tomasz.figa@...il.com>,
	'Thomas Abraham' <thomas.abraham@...aro.org>,
	'Olof Johansson' <olof@...om.net>,
	'Vikas Sajjan' <vikas.sajjan@...aro.org>,
	'Yadwinder Singh Brar' <yadi.brar01@...il.com>,
	'linux-samsung-soc' <linux-samsung-soc@...r.kernel.org>,
	'Mike Turquette' <mturquette@...aro.org>,
	'Tomasz Figa' <t.figa@...sung.com>,
	linux-kernel@...r.kernel.org
Subject: RE: [PATCH] clk: samsung: Fix pll36xx_recalc_rate to handle kdiv
 properly

Doug Anderson wrote:
> 
> The KDIV value is often listed as unsigned but it needs to be treated
> as a 16-bit signed value when using it in calculations.  Fix our rate
> recalculation to do this correctly.
> 
> Before doing this, I tried setting EPLL on exynos5250 to:
>   rate, m, p, s, k = 80000000, 107, 2, 4, 43691
> 
> This rate is exactly from the table in the exynos5250 user manual.
> 
> I read this back as 80750003 with:
>   cat /sys/kernel/debug/clk/fin_pll/fout_epll/clk_rate
> 
> After this patch, it reads back as 80000003
> 
>   mw 0x10020130 a06b0204
>   mw 0x10020134 0000aaab
> 
> Signed-off-by: Doug Anderson <dianders@...omium.org>

Yeah,

Acked-by: Kukjin Kim <kgene.kim@...sung.com>

Mike, please apply in your fixes.

Thanks.

- Kukjin

> ---
> This patch is based upon another in-flight patch to avoid conflicts:
>   clk: samsung: Use clk->base instead of directly using clk->con0 for
> PLL3xxx
>   https://patchwork.kernel.org/patch/2629751/
> 
>  drivers/clk/samsung/clk-pll.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/samsung/clk-pll.c b/drivers/clk/samsung/clk-pll.c
> index 01f17cf..26416bb 100644
> --- a/drivers/clk/samsung/clk-pll.c
> +++ b/drivers/clk/samsung/clk-pll.c
> @@ -115,7 +115,8 @@ static unsigned long
> samsung_pll36xx_recalc_rate(struct clk_hw *hw,
>  				unsigned long parent_rate)
>  {
>  	struct samsung_clk_pll *pll = to_clk_pll(hw);
> -	u32 mdiv, pdiv, sdiv, kdiv, pll_con0, pll_con1;
> +	u32 mdiv, pdiv, sdiv, pll_con0, pll_con1;
> +	s16 kdiv;
>  	u64 fvco = parent_rate;
> 
>  	pll_con0 = pll_readl(pll, PLL36XX_CON0_OFFSET);
> @@ -123,7 +124,7 @@ static unsigned long
> samsung_pll36xx_recalc_rate(struct clk_hw *hw,
>  	mdiv = (pll_con0 >> PLL36XX_MDIV_SHIFT) & PLL36XX_MDIV_MASK;
>  	pdiv = (pll_con0 >> PLL36XX_PDIV_SHIFT) & PLL36XX_PDIV_MASK;
>  	sdiv = (pll_con0 >> PLL36XX_SDIV_SHIFT) & PLL36XX_SDIV_MASK;
> -	kdiv = pll_con1 & PLL36XX_KDIV_MASK;
> +	kdiv = (s16)(pll_con1 & PLL36XX_KDIV_MASK);
> 
>  	fvco *= (mdiv << 16) + kdiv;
>  	do_div(fvco, (pdiv << sdiv));
> --
> 1.8.2.1

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