[PATCH v3 1/1] clk: meson: meson8b: add support for the NAND clocks

[Jerome Brunet]

On Sun, 2018-04-22 at 12:33 +0200, Martin Blumenstingl wrote:
> This adds the NAND clocks (from the HHI_NAND_CLK_CNTL register) to the
> Meson8b clock driver. There are three NAND clocks: a gate which enables
> or disables the NAND clock, a mux and a divider (which divides the mux
> output).
> Unfortunately the public S805 datasheet does not document the mux
> parents. However, the vendor kernel has a few hints for us which allows
> us to make an educated guess about the clock parents. To do this we need
> to have a look at set_nand_core_clk() from the vendor's NAND driver (see
> [0]):
> - XTAL = (4<<9) | (1<<8) | 0
> - 160MHz = (0<<9) | (1<<8) | 3)
> - 182MHz = (3<<9) | (1<<8) | 1)
> - 212MHz = (1<<9) | (1<<8) | 3)
> - 255MHz = (2<<9) | (1<<8) | 1)
> 
> While there is a comment for the XTAL parent (which indicates that it
> should only be used for debugging) we have to do a bit of math for the
> other parents: target_freq * divider = rate of parent clock
> Bit 8 above is the enable bit, so we can ignore it here. Bits 11:9 are
> the mux index and bits 6:0 are the 0-based divider (so we need to add
> 1). This gives us:
> - mux 0 (160MHz * 4) = fclk_div4 (actual rate = 637.5MHz, off by 2.5MHz)
> - mux 1 (212MHz * 4) = fclk_div3 (actual rate = 850MHz, off by 2MHz)
> - mux 2 (255MHz * 2) = fclk_div5 (matches exactly 510MHz)
> - mux 3 (182MHz * 2) = fclk_div7 (actual rate = 346.3MHz, off by 0.3MHz)
> 
> [0] https://github.com/khadas/linux/blob/9587681285cb/drivers/amlogic/amlnf/dev/amlnf_ctrl.c#L314
> 
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl at googlemail.com>
> ---
>  drivers/clk/meson/meson8b.c              | 54 ++++++++++++++++++++++++
>  drivers/clk/meson/meson8b.h              |  3 +-
>  include/dt-bindings/clock/meson8b-clkc.h |  3 ++
>  3 files changed, 59 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/meson/meson8b.c b/drivers/clk/meson/meson8b.c
> index 2c4ff6192852..3f726ff73261 100644
> --- a/drivers/clk/meson/meson8b.c
> +++ b/drivers/clk/meson/meson8b.c
> @@ -639,6 +639,54 @@ static struct clk_regmap meson8b_cpu_clk = {
>  	},
>  };
>  
> +static struct clk_regmap meson8b_nand_clk_sel = {
> +	.data = &(struct clk_regmap_mux_data){
> +		.offset = HHI_NAND_CLK_CNTL,
> +		.mask = 0x7,
> +		.shift = 9,
> +		.flags = CLK_MUX_ROUND_CLOSEST,

Maybe you have seen it already, but there was a problem with this flag, it was
ignored. Fix should land in this cycle.

https://lkml.kernel.org/r/152389589448.51482.15489333464741262913@swboyd.mtv.cor
p.google.com

> +	},
> +	.hw.init = &(struct clk_init_data){
> +		.name = "nand_clk_sel",
> 

[...]

>  /*
>   * include the CLKID and RESETID that have
> diff --git a/include/dt-bindings/clock/meson8b-clkc.h b/include/dt-bindings/clock/meson8b-clkc.h
> index dea9d46d4fa7..434d7ba63801 100644
> --- a/include/dt-bindings/clock/meson8b-clkc.h
> +++ b/include/dt-bindings/clock/meson8b-clkc.h
> @@ -102,5 +102,8 @@
>  #define CLKID_MPLL0		93
>  #define CLKID_MPLL1		94
>  #define CLKID_MPLL2		95
> +#define CLKID_NAND_SEL		110
> +#define CLKID_NAND_DIV		111

Nitpick: Could put the bindings in separate patch ?
It makes our life easier if intend to push a DT patch using them in this cycle.

Also, do you need to expose the divider and the mux ?

Apart from this, patch looks good to me.

Acked-by: Jerome Brunet <jbrunet at baylibre.com>

> +#define CLKID_NAND_CLK		112
>  
>  #endif /* __MESON8B_CLKC_H */