[U-Boot] [PATCH 11/25] clk: Allow clock defaults to be set also during re-reloc state

[Andreas Dannenberg]

Philipp,

On Fri, Aug 24, 2018 at 04:42:15PM +0200, Dr. Philipp Tomsich wrote:
> +Kever
> 
> > On 24 Aug 2018, at 16:12, Tom Rini <trini at konsulko.com> wrote:
> > 
> > On Tue, Aug 21, 2018 at 08:01:49PM +0530, Lokesh Vutla wrote:
> > 
> >> From: Andreas Dannenberg <dannenberg at ti.com>
> >> 
> >> The earlier commit f4fcba5c5ba ("clk: implement clk_set_defaults()")
> >> which introduced the functionality for setting clock defaults such as
> >> rates and parents will skip the processing when executing in a re-reloc
> >> state. This for example can prevent the assigning of clock parents
> >> when running in SPL code. Go ahead and remove this limitation.
> >> 
> >> Signed-off-by: Andreas Dannenberg <dannenberg at ti.com>
> >> Signed-off-by: Lokesh Vutla <lokeshvutla at ti.com>
> >> ---
> >> drivers/clk/clk-uclass.c | 4 ----
> >> 1 file changed, 4 deletions(-)
> >> 
> >> diff --git a/drivers/clk/clk-uclass.c b/drivers/clk/clk-uclass.c
> >> index 2b15978e14..04b369aa5a 100644
> >> --- a/drivers/clk/clk-uclass.c
> >> +++ b/drivers/clk/clk-uclass.c
> >> @@ -243,10 +243,6 @@ int clk_set_defaults(struct udevice *dev)
> >> {
> >> 	int ret;
> >> 
> >> -	/* If this is running pre-reloc state, don't take any action. */
> >> -	if (!(gd->flags & GD_FLG_RELOC))
> >> -		return 0;
> >> -
> >> 	debug("%s(%s)\n", __func__, dev_read_name(dev));
> >> 
> >> 	ret = clk_set_default_parents(dev);
> > 
> > Philipp? David?  Comments?  Thanks!
> 
> If I remember correctly, David had a concern regarding an increase in
> boottime if we ran this twice… adding Kever, as he was also involved
> in the discussion.
> 
> I settled on skipping it for pre-reloc, but it’s an imperfect solution: the
> boottime increase comes from the fact that some devices have a large
> number of assigned-clocks, that the device-tree processing has a cost,
> and that we don’t have a way of synchronising between SPL and full
> U-Boot to avoid redoing the complete init-flow.

Good to know some of the background; when I did this patch initially it
was not really clear why this was removed and it obviously was an issue
for what I was doing that I had to overcome and re-adding this was the
simpliest thing to do at that time.

> Maybe we should have a SPL-specific property for the assigned-clocks
> to be set pre-reloc?

Need to think about this some more. Generally we probably want to do as
little as possible before relocation. Unfortunately for the K3 family of
SoCs much is dependent on loading/installing the system firmware (SYSFW)
image including to get DDR operational which itself requires us to use a
lot of DT/DM stuff pre-reloc. So a little bit of a chicken and egg
problem...

--
Andreas Dannenberg
Texas Instruments Inc