[U-Boot] [PATCH 1/3] aspeed: ast2500: Add AHB clock

[Joel Stanley]

On Mon, 10 Sep 2018 at 23:48, Cédric Le Goater <clg at kaod.org> wrote:
>
> The AHB clock is used by the FMC/SPI controllers.
>
> Signed-off-by: Cédric Le Goater <clg at kaod.org>
> ---
>  arch/arm/include/asm/arch-aspeed/scu_ast2500.h |  2 ++
>  include/dt-bindings/clock/ast2500-scu.h        |  1 +
>  drivers/clk/aspeed/clk_ast2500.c               | 12 ++++++++++++
>  3 files changed, 15 insertions(+)
>
> diff --git a/arch/arm/include/asm/arch-aspeed/scu_ast2500.h b/arch/arm/include/asm/arch-aspeed/scu_ast2500.h
> index 4988ced7ddcc..6a90ded752ad 100644
> --- a/arch/arm/include/asm/arch-aspeed/scu_ast2500.h
> +++ b/arch/arm/include/asm/arch-aspeed/scu_ast2500.h
> @@ -11,6 +11,8 @@
>  #define SCU_HWSTRAP_VGAMEM_MASK                (3 << SCU_HWSTRAP_VGAMEM_SHIFT)
>  #define SCU_HWSTRAP_MAC1_RGMII         (1 << 6)
>  #define SCU_HWSTRAP_MAC2_RGMII         (1 << 7)
> +#define SCU_HWSTRAP_AXIAHB_DIV_SHIFT   9
> +#define SCU_HWSTRAP_AXIAHB_DIV_MASK    (0x7 << SCU_HWSTRAP_AXIAHB_DIV_SHIFT)
>  #define SCU_HWSTRAP_DDR4               (1 << 24)
>  #define SCU_HWSTRAP_CLKIN_25MHZ                (1 << 23)
>
> diff --git a/include/dt-bindings/clock/ast2500-scu.h b/include/dt-bindings/clock/ast2500-scu.h
> index 4803abe9f628..03e6d16d3de0 100644
> --- a/include/dt-bindings/clock/ast2500-scu.h
> +++ b/include/dt-bindings/clock/ast2500-scu.h
> @@ -17,6 +17,7 @@
>  #define BCLK_MACCLK    103
>  #define BCLK_SDCLK     104
>  #define BCLK_ARMCLK    105
> +#define BCLK_HCLK      106

I like how the clocks are grouped in this file. Are we confident that
HCLK is going in the correct spot?

>  #define MCLK_DDR       201
>
> diff --git a/drivers/clk/aspeed/clk_ast2500.c b/drivers/clk/aspeed/clk_ast2500.c
> index 526470051c5d..c55f8d5ae30d 100644
> --- a/drivers/clk/aspeed/clk_ast2500.c
> +++ b/drivers/clk/aspeed/clk_ast2500.c
> @@ -143,6 +143,18 @@ static ulong ast2500_clk_get_rate(struct clk *clk)
>                         rate = rate / apb_div;
>                 }
>                 break;
> +       case BCLK_HCLK:
> +               {
> +                       ulong ahb_div = 1 + ((readl(&priv->scu->hwstrap)
> +                                             & SCU_HWSTRAP_AXIAHB_DIV_MASK)
> +                                            >> SCU_HWSTRAP_AXIAHB_DIV_SHIFT);
> +                       ulong axi_div = 2;
> +
> +                       rate = ast2500_get_hpll_rate(
> +                               clkin, readl(&priv->scu->h_pll_param));
> +                       rate = rate / axi_div / ahb_div;

In the kernel driver I wrote it as:

 rate / (axi_div + ahb_div)

I know that the maths works, but do the numbers come out as we expect
when doing integer division?