linux-kernel - Re: [PATCH v2 04/10] clk: qcom: Add support for PLLs with alpha mode

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Message-ID: <20160824061540.GU6502@codeaurora.org>
Date:   Tue, 23 Aug 2016 23:15:40 -0700
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Rajendra Nayak <rnayak@...eaurora.org>
Cc:     mturquette@...libre.com, linux-clk@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        tdas@...eaurora.org
Subject: Re: [PATCH v2 04/10] clk: qcom: Add support for PLLs with alpha mode

On 08/11, Rajendra Nayak wrote:
> Some PLLs can support an alpha mode, and a single alpha
> register (instead of registers to program the M/N values),
> the contents of which depend on the alpha mode selected.
> (They are either treated as two's complement or M/N value)

That's just a sentence, so please drop the parentheses.

> Add support for this in the clk PLL driver.
> 

I'm confused, don't we already have clk-alpha-pll.c to handle
alpha type plls? What are we doing adding support to the "legacy"
pll code?

> Signed-off-by: Rajendra Nayak <rnayak@...eaurora.org>
> ---
>  drivers/clk/qcom/clk-pll.c | 8 ++++++--
>  drivers/clk/qcom/clk-pll.h | 2 ++
>  2 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/qcom/clk-pll.c b/drivers/clk/qcom/clk-pll.c
> index 5b940d6..08d2fa2 100644
> --- a/drivers/clk/qcom/clk-pll.c
> +++ b/drivers/clk/qcom/clk-pll.c
> @@ -255,8 +255,12 @@ static void clk_pll_configure(struct clk_pll *pll, struct regmap *regmap,
>  	u32 mask;
>  
>  	regmap_write(regmap, pll->l_reg, config->l);
> -	regmap_write(regmap, pll->m_reg, config->m);
> -	regmap_write(regmap, pll->n_reg, config->n);
> +	if (pll->alpha_reg) {

This assumes that alpha_reg is not 0 offset from base, which
seems like a bad assumption to make.

> +		regmap_write(regmap, pll->alpha_reg, config->alpha);
> +	} else {
> +		regmap_write(regmap, pll->m_reg, config->m);
> +		regmap_write(regmap, pll->n_reg, config->n);
> +	}
>  
>  	val = config->vco_val;
>  	val |= config->pre_div_val;
> 

-- 
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