linux-kernel - Re: [PATCH v5 10/27] clk: at91: sam9x7: add support for HW PLL freq dividers

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Message-ID: <c39a3967-1089-4113-917e-78fc14e788bf@tuxon.dev>
Date: Mon, 15 Jul 2024 11:06:39 +0300
From: claudiu beznea <claudiu.beznea@...on.dev>
To: Varshini Rajendran <varshini.rajendran@...rochip.com>,
 mturquette@...libre.com, sboyd@...nel.org, nicolas.ferre@...rochip.com,
 alexandre.belloni@...tlin.com, linux-clk@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 10/27] clk: at91: sam9x7: add support for HW PLL freq
 dividers



On 03.07.2024 13:27, Varshini Rajendran wrote:
> Add support for hardware dividers for PLL IDs in sam9x7 SoC. The system
> PLL - PLLA and the system PLL divided by 2 - PLLADIV2 with PLL ID 0 and
> 4 respectively, both have a hardware divider /2. This has to be taken into
> account in the software to obtain the right frequencies. Support for the
> same is added in the PLL driver.
> 
> fcorepllack -----> HW Div = 2 -+--> fpllack
>                                |
>                                +--> HW Div = 2 ---> fplladiv2ck
> 
> In this case the corepll freq is 1600 MHz. So, the plla freq is 800 MHz
> after the hardware divider and the plladiv2 freq is 400 MHz after the
> hardware divider (given that the DIVPMC is 0).
> 
> Signed-off-by: Varshini Rajendran <varshini.rajendran@...rochip.com>

Reviewed-by: Claudiu Beznea <claudiu.beznea@...on.dev>

> ---
> Changes in v5:
> - Corrected typos in commit message.
> - Rewrote the conditional statement.
> ---
>  drivers/clk/at91/clk-sam9x60-pll.c | 30 ++++++++++++++++++++++++++++--
>  drivers/clk/at91/pmc.h             |  1 +
>  2 files changed, 29 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/at91/clk-sam9x60-pll.c b/drivers/clk/at91/clk-sam9x60-pll.c
> index b0314dfd7393..fda041102224 100644
> --- a/drivers/clk/at91/clk-sam9x60-pll.c
> +++ b/drivers/clk/at91/clk-sam9x60-pll.c
> @@ -73,9 +73,15 @@ static unsigned long sam9x60_frac_pll_recalc_rate(struct clk_hw *hw,
>  {
>  	struct sam9x60_pll_core *core = to_sam9x60_pll_core(hw);
>  	struct sam9x60_frac *frac = to_sam9x60_frac(core);
> +	unsigned long freq;
>  
> -	return parent_rate * (frac->mul + 1) +
> +	freq = parent_rate * (frac->mul + 1) +
>  		DIV_ROUND_CLOSEST_ULL((u64)parent_rate * frac->frac, (1 << 22));
> +
> +	if (core->layout->div2)
> +		freq >>= 1;
> +
> +	return freq;
>  }
>  
>  static int sam9x60_frac_pll_set(struct sam9x60_pll_core *core)
> @@ -432,6 +438,12 @@ static unsigned long sam9x60_div_pll_recalc_rate(struct clk_hw *hw,
>  	return DIV_ROUND_CLOSEST_ULL(parent_rate, (div->div + 1));
>  }
>  
> +static unsigned long sam9x60_fixed_div_pll_recalc_rate(struct clk_hw *hw,
> +						       unsigned long parent_rate)
> +{
> +	return parent_rate >> 1;
> +}
> +
>  static long sam9x60_div_pll_compute_div(struct sam9x60_pll_core *core,
>  					unsigned long *parent_rate,
>  					unsigned long rate)
> @@ -606,6 +618,16 @@ static const struct clk_ops sam9x60_div_pll_ops_chg = {
>  	.restore_context = sam9x60_div_pll_restore_context,
>  };
>  
> +static const struct clk_ops sam9x60_fixed_div_pll_ops = {
> +	.prepare = sam9x60_div_pll_prepare,
> +	.unprepare = sam9x60_div_pll_unprepare,
> +	.is_prepared = sam9x60_div_pll_is_prepared,
> +	.recalc_rate = sam9x60_fixed_div_pll_recalc_rate,
> +	.round_rate = sam9x60_div_pll_round_rate,
> +	.save_context = sam9x60_div_pll_save_context,
> +	.restore_context = sam9x60_div_pll_restore_context,
> +};
> +
>  struct clk_hw * __init
>  sam9x60_clk_register_frac_pll(struct regmap *regmap, spinlock_t *lock,
>  			      const char *name, const char *parent_name,
> @@ -725,10 +747,14 @@ sam9x60_clk_register_div_pll(struct regmap *regmap, spinlock_t *lock,
>  	else
>  		init.parent_names = &parent_name;
>  	init.num_parents = 1;
> -	if (flags & CLK_SET_RATE_GATE)
> +
> +	if (layout->div2)
> +		init.ops = &sam9x60_fixed_div_pll_ops;
> +	else if (flags & CLK_SET_RATE_GATE)
>  		init.ops = &sam9x60_div_pll_ops;
>  	else
>  		init.ops = &sam9x60_div_pll_ops_chg;
> +
>  	init.flags = flags;
>  
>  	div->core.id = id;
> diff --git a/drivers/clk/at91/pmc.h b/drivers/clk/at91/pmc.h
> index bb9da35198d9..91d1c6305d95 100644
> --- a/drivers/clk/at91/pmc.h
> +++ b/drivers/clk/at91/pmc.h
> @@ -64,6 +64,7 @@ struct clk_pll_layout {
>  	u8 frac_shift;
>  	u8 div_shift;
>  	u8 endiv_shift;
> +	u8 div2;
>  };
>  
>  extern const struct clk_pll_layout at91rm9200_pll_layout;