[U-Boot] Clock tree in U-Boot

[Simon Glass]

Hi Eric,

On 17 April 2015 at 10:12, Eric Nelson <eric.nelson at boundarydevices.com> wrote:
> Hi all,
>
> Heiko's recent patch set [1] to control the LDB clock on i.MX5/6 boards
> makes it painfully obvious that some semblance of clock tree is needed,
> even if it starts off as a shell.
>
> We currently have routines declared in [2] that should be moved into
> a more common spot:
>
>         void clk_enable(struct clk *clk);
>         void clk_disable(struct clk *clk);
>         u32 clk_get_rate(struct clk *clk);
>         int clk_set_rate(struct clk *clk, unsigned long rate);
>         long clk_round_rate(struct clk *clk, unsigned long rate);
>         int clk_set_parent(struct clk *clk, struct clk *parent);
>         int clk_get_usecount(struct clk *clk);
>         struct clk *clk_get_parent(struct clk *clk);
>
> Can we get some agreement on a proper subset of [3] that's appropriate
> for use in U-Boot?
>
> My thought is that the list above, plus some form of clk_get() and/or
> clk_get_sys() would be a good start.
>
> Please advise,

I'd like to see this. It should use driver model I think. The above
list looks good to me.

For clk_get(), we could support claiming of clocks so we know when we
can turn off its parent / automatically enable it / etc. But perhaps
as a first step just implementing a uclass and a driver for one device
would be a good start.

>
>
> Eric
>
> [1] http://lists.denx.de/pipermail/u-boot/2015-April/thread.html#210677
> [2] http://git.denx.de/?p=u-boot.git;a=blob;f=drivers/video/ipu.h#l245
> [3]
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/include/linux/clk.h?id=refs/tags/v4.0

Regards,
Simon