Re: [PATCH 1/3] clk: ti: add 'ti,round-rate' flag

[Tero Kristo <t-kristo@ti.com>]

On 05/08/2014 12:06 PM, Tomi Valkeinen wrote:
> The current DPLL code does not try to round the clock rate, and instead
> returns an error if the requested clock rate cannot be produced exactly
> by the DPLL.
>
> It could be argued that this is a bug, but as the current drivers may
> depend on that behavior, a new flag 'ti,round-rate' is added which
> enables clock rate rounding.

Someone could probably argue that this flag is not a hardware feature, 
but instead is used to describe linux-kernel behavior, and would 
probably be frowned upon by the DT enthusiasts. Othen than that, I like 
this approach better than a global setting, but would like second 
opinions here.

-Tero

>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
> ---
>   Documentation/devicetree/bindings/clock/ti/dpll.txt | 2 ++
>   drivers/clk/ti/dpll.c                               | 3 +++
>   include/linux/clk/ti.h                              | 1 +
>   3 files changed, 6 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/clock/ti/dpll.txt b/Documentation/devicetree/bindings/clock/ti/dpll.txt
> index 30bfdb7c9f18..7912d876e858 100644
> --- a/Documentation/devicetree/bindings/clock/ti/dpll.txt
> +++ b/Documentation/devicetree/bindings/clock/ti/dpll.txt
> @@ -48,6 +48,8 @@ Optional properties:
>   	- ti,low-power-stop : DPLL supports low power stop mode, gating output
>   	- ti,low-power-bypass : DPLL output matches rate of parent bypass clock
>   	- ti,lock : DPLL locks in programmed rate
> +- ti,round-rate : if not set, the dpll will return an error if asked for a
> +                  clock rate that it cannot produce exactly.
>
>   Examples:
>   	dpll_core_ck: dpll_core_ck@44e00490 {
> diff --git a/drivers/clk/ti/dpll.c b/drivers/clk/ti/dpll.c
> index 7e498a44f97d..c5858c46b58c 100644
> --- a/drivers/clk/ti/dpll.c
> +++ b/drivers/clk/ti/dpll.c
> @@ -265,6 +265,9 @@ static void __init of_ti_dpll_setup(struct device_node *node,
>   	if (dpll_mode)
>   		dd->modes = dpll_mode;
>
> +	if (of_property_read_bool(node, "ti,round-rate"))
> +		clk_hw->flags |= DPLL_USE_ROUNDED_RATE;
> +
>   	ti_clk_register_dpll(&clk_hw->hw, node);
>   	return;
>
> diff --git a/include/linux/clk/ti.h b/include/linux/clk/ti.h
> index 4a21a872dbbd..79e8a7876457 100644
> --- a/include/linux/clk/ti.h
> +++ b/include/linux/clk/ti.h
> @@ -155,6 +155,7 @@ struct clk_hw_omap {
>   #define INVERT_ENABLE		(1 << 4)	/* 0 enables, 1 disables */
>   #define CLOCK_CLKOUTX2		(1 << 5)
>   #define MEMMAP_ADDRESSING	(1 << 6)
> +#define DPLL_USE_ROUNDED_RATE	(1 << 7)	/* dpll's round_rate() returns rounded rate */
>
>   /* CM_CLKEN_PLL*.EN* bit values - not all are available for every DPLL */
>   #define DPLL_LOW_POWER_STOP	0x1
>