linux-kernel - Re: [PATCH 07/19] clk: at91: sam9x60-pll: use frac when setting frequency

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Message-ID: <20200717091238.GL3428@piout.net>
Date:   Fri, 17 Jul 2020 11:12:38 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Claudiu Beznea <claudiu.beznea@...rochip.com>
Cc:     mturquette@...libre.com, sboyd@...nel.org,
        nicolas.ferre@...rochip.com, ludovic.desroches@...rochip.com,
        bbrezillon@...nel.org, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 07/19] clk: at91: sam9x60-pll: use frac when setting
 frequency

On 15/07/2020 14:24:15+0300, Claudiu Beznea wrote:
> In commit a436c2a447e59 ("clk: at91: add sam9x60 PLL driver")
> the fractional part of PLL wasn't set on registers but it was
> calculated and taken into account for determining div and mul
> (see sam9x60_pll_get_best_div_mul()).
> 

I think this becomes an issue only once 4/19 is applied so you should
probably squash those two together.

> Fixes: a436c2a447e59 ("clk: at91: add sam9x60 PLL driver")
> Signed-off-by: Claudiu Beznea <claudiu.beznea@...rochip.com>
> ---
>  drivers/clk/at91/clk-sam9x60-pll.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/clk/at91/clk-sam9x60-pll.c b/drivers/clk/at91/clk-sam9x60-pll.c
> index 00f2afd6e9b6..13e15bd48770 100644
> --- a/drivers/clk/at91/clk-sam9x60-pll.c
> +++ b/drivers/clk/at91/clk-sam9x60-pll.c
> @@ -16,6 +16,7 @@
>  
>  #define	PMC_PLL_CTRL0_DIV_MSK	GENMASK(7, 0)
>  #define	PMC_PLL_CTRL1_MUL_MSK	GENMASK(31, 24)
> +#define	PMC_PLL_CTRL1_FRACR_MSK	GENMASK(21, 0)
>  
>  #define PLL_DIV_MAX		(FIELD_GET(PMC_PLL_CTRL0_DIV_MSK, UINT_MAX) + 1)
>  #define UPLL_DIV		2
> @@ -55,7 +56,7 @@ static int sam9x60_pll_prepare(struct clk_hw *hw)
>  	unsigned long flags;
>  	u8 div;
>  	u16 mul;
> -	u32 val;
> +	u32 val, frac;
>  
>  	spin_lock_irqsave(pll->lock, flags);
>  	regmap_write(regmap, AT91_PMC_PLL_UPDT, pll->id);
> @@ -65,9 +66,10 @@ static int sam9x60_pll_prepare(struct clk_hw *hw)
>  
>  	regmap_read(regmap, AT91_PMC_PLL_CTRL1, &val);
>  	mul = FIELD_GET(PMC_PLL_CTRL1_MUL_MSK, val);
> +	frac = FIELD_GET(PMC_PLL_CTRL1_FRACR_MSK, val);
>  
>  	if (sam9x60_pll_ready(regmap, pll->id) &&
> -	    (div == pll->div && mul == pll->mul)) {
> +	    (div == pll->div && mul == pll->mul && frac == pll->frac)) {
>  		spin_unlock_irqrestore(pll->lock, flags);
>  		return 0;
>  	}
> @@ -80,7 +82,8 @@ static int sam9x60_pll_prepare(struct clk_hw *hw)
>  	regmap_write(regmap, AT91_PMC_PLL_ACR, val);
>  
>  	regmap_write(regmap, AT91_PMC_PLL_CTRL1,
> -		     FIELD_PREP(PMC_PLL_CTRL1_MUL_MSK, pll->mul));
> +		     FIELD_PREP(PMC_PLL_CTRL1_MUL_MSK, pll->mul) |
> +		     FIELD_PREP(PMC_PLL_CTRL1_FRACR_MSK, pll->frac));
>  
>  	if (pll->characteristics->upll) {
>  		/* Enable the UTMI internal bandgap */
> -- 
> 2.7.4
> 

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com