[PATCH linux dev-4.17 v3] clk: aspeed: Support HPLL strapping on ast2400

[Cédric Le Goater]

On 06/21/2018 10:43 AM, Joel Stanley wrote:
> The HPLL can be configured through a register (SCU24), however some
> platforms chose to configure it through the strapping settings and do
> not use the register. This was not noticed as the logic for bit 18 in
> SCU24 was confused: set means programmed, but the driver read it as set
> means strapped.
> 
> This gives us the correct HPLL value on Palmetto systems, from which
> most of the peripheral clocks are generated.
> 
> Signed-off-by: Joel Stanley <joel at jms.id.au>
> ---
> v2: Fix comment and commit message
> v3: Support 25MHz clkin by changing the way the calculations
> ---
>  drivers/clk/clk-aspeed.c | 45 +++++++++++++++++++++++++---------------
>  1 file changed, 28 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/clk/clk-aspeed.c b/drivers/clk/clk-aspeed.c
> index c17032bc853a..5deb246c0184 100644
> --- a/drivers/clk/clk-aspeed.c
> +++ b/drivers/clk/clk-aspeed.c
> @@ -24,7 +24,7 @@
>  #define ASPEED_MPLL_PARAM	0x20
>  #define ASPEED_HPLL_PARAM	0x24
>  #define  AST2500_HPLL_BYPASS_EN	BIT(20)
> -#define  AST2400_HPLL_STRAPPED	BIT(18)
> +#define  AST2400_HPLL_PROGRAMMED BIT(18)
>  #define  AST2400_HPLL_BYPASS_EN	BIT(17)
>  #define ASPEED_MISC_CTRL	0x2c
>  #define  UART_DIV13_EN		BIT(12)
> @@ -565,29 +565,40 @@ builtin_platform_driver(aspeed_clk_driver);
>  static void __init aspeed_ast2400_cc(struct regmap *map)
>  {
>  	struct clk_hw *hw;
> -	u32 val, freq, div;
> +	u32 val, reg, div, clkin, hpll;
> +	const u16 hpll_rates[][4] = {
> +		{384, 360, 336, 408},
> +		{400, 375, 350, 425},
> +	};
> +	int rate;
>  
>  	/*
>  	 * CLKIN is the crystal oscillator, 24, 48 or 25MHz selected by
>  	 * strapping
>  	 */
> -	regmap_read(map, ASPEED_STRAP, &val);
> -	if (val & CLKIN_25MHZ_EN)
> -		freq = 25000000;
> -	else if (val & AST2400_CLK_SOURCE_SEL)
> -		freq = 48000000;
> +	regmap_read(map, ASPEED_STRAP, &reg);
> +	rate = (reg >> 8) & 3;
> +	if (reg & CLKIN_25MHZ_EN) {
> +		clkin = 25000000;
> +		hpll = hpll_rates[1][rate];
> +	} else if (reg & AST2400_CLK_SOURCE_SEL) {
> +		clkin = 48000000;
> +		hpll = hpll_rates[0][rate];
> +	} else {
> +		clkin = 24000000;
> +		hpll = hpll_rates[0][rate];
> +	}
> +	hw = clk_hw_register_fixed_rate(NULL, "clkin", NULL, 0, clkin);
> +	pr_debug("clkin @%u MHz\n", clkin / 1000000);
> +
> +	regmap_read(map, ASPEED_HPLL_PARAM, &reg);
> +	if (reg & AST2400_HPLL_PROGRAMMED)
> +		hw = aspeed_ast2400_calc_pll("hpll", val);

There is still a problem here. We want to compute the hpll freq using
a 24MHz base and not the clkin frequency which is strapped in SCU70.
May be use "fixed-24m" in aspeed_ast2400_calc_pll() ? 

>  	else
> -		freq = 24000000;
> -	hw = clk_hw_register_fixed_rate(NULL, "clkin", NULL, 0, freq);
> -	pr_debug("clkin @%u MHz\n", freq / 1000000);
> +		hw = clk_hw_register_fixed_rate(NULL, "hpll", "clkin", 0,
> +				hpll * 1000000);

The hpll clock being strapped, I am not sure it can be attached to "clkin".

C. 

> -	/*
> -	 * High-speed PLL clock derived from the crystal. This the CPU clock,
> -	 * and we assume that it is enabled
> -	 */
> -	regmap_read(map, ASPEED_HPLL_PARAM, &val);
> -	WARN(val & AST2400_HPLL_STRAPPED, "hpll is strapped not configured");
> -	aspeed_clk_data->hws[ASPEED_CLK_HPLL] = aspeed_ast2400_calc_pll("hpll", val);
> +	aspeed_clk_data->hws[ASPEED_CLK_HPLL] = hw;
>  
>  	/*
>  	 * Strap bits 11:10 define the CPU/AHB clock frequency ratio (aka HCLK)
>