Re: [RFC PATCH] clk: ti: set CLK_SET_RATE_NO_REPARENT for ti,mux-clock

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

On 06/17/2014 11:04 AM, Tomi Valkeinen wrote:
> When setting the rate of a clock, by default the clock framework will
> change the parent of the clock to the most suitable one in
> __clk_mux_determine_rate() (most suitable by looking at the clock rate).
>
> This is a rather dangerous default, and causes problems on AM43x when
> using display and ethernet. There are multiple ways to select the clock
> muxes on AM43x, and some of those clock paths have the same source
> clocks for display and ethernet. When changing the clock rate for the
> display subsystem, the clock framework decides to change the display mux
> from the dedicated display PLL to a shared PLL which is used by the
> ethernet, and then changes the rate of the shared PLL, breaking the
> ethernet.
>
> As I don't think there ever is a case where we want the clock framework
> to automatically change the parent clock of a clock mux, this patch sets
> the CLK_SET_RATE_NO_REPARENT for all ti,mux-clocks.
>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
> ---
>   drivers/clk/ti/mux.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/clk/ti/mux.c b/drivers/clk/ti/mux.c
> index 0197a478720c..e9d650e51287 100644
> --- a/drivers/clk/ti/mux.c
> +++ b/drivers/clk/ti/mux.c
> @@ -160,7 +160,7 @@ static void of_mux_clk_setup(struct device_node *node)
>   	u8 clk_mux_flags = 0;
>   	u32 mask = 0;
>   	u32 shift = 0;
> -	u32 flags = 0;
> +	u32 flags = CLK_SET_RATE_NO_REPARENT;

I am fine with this approach, as it seems pretty much all the other 
mux-clock users are setting this flag also. The TI clocks have had this 
way of using mux clocks from the legacy times... might just be a design 
flaw.

-Tero

>
>   	num_parents = of_clk_get_parent_count(node);
>   	if (num_parents < 2) {
>