On 8/16/22 10:20, Andy Shevchenko wrote:
On Mon, Aug 15, 2022 at 10:42 AM Uwe Kleine-König
<u.kleine-koenig@xxxxxxxxxxxxxx> wrote:
On Mon, Aug 15, 2022 at 10:30:45AM +0300, Andy Shevchenko wrote:
On Mon, Aug 15, 2022 at 12:31 AM Uwe Kleine-König
<u.kleine-koenig@xxxxxxxxxxxxxx> wrote:
On Sun, Aug 14, 2022 at 10:01:08PM +0300, Andy Shevchenko wrote:
On Sat, Aug 13, 2022 at 7:21 PM Jonathan Cameron <jic23@xxxxxxxxxx> wrote:
On Mon, 8 Aug 2022 22:47:33 +0200
Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> wrote:
Make use of devm_clk_get_enabled() to replace some code that effectively
open codes this new function.
Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
This might have side effects as it now enables the clock before calling
the clk_set_rate(). Also changes the clock start up ordering. Neither is that
scary a change, but on really fussy hardware they might cause problems.
Add a few rock-chips people who have sent patches in last few years
to hopefully take a look or even better run a test.
I believe you found a bug in the patch. The possible solutions are:
- not take the patch
- disable and re-enable clock around clk_set_rate()
IIRC clk_set_rate() will spit a WARN if clock is enabled.
You mean in general? I think that's wrong. There might be some clks that
do that, but I'd consider them strange. If you ask me, calling
clk_set_rate() for a *disabled* clk is the strange concept ...
I think it's correct from the logic and electrical perspective. That's
why the preparation and enablement are separated in CCF. But please
double check, because I can't remember everything by heart.
In my book the separation is done because "enabling" has to sleep for
some clks (e.g. PLLs) while a sleeping clk_enable() is bad for various
use cases and most clks don't sleep for enabling.
Yeah, but the idea of changing clock rate on the fly may produce
interesting side-effects on hardware level (with PLL latencies to lock
the phase and possible glitches). So, changing clock against enabled
hardware (not in reset / power off state) seems not a good idea.
The clk_set_rate() API will internally disable the clock, if the clock
chip requires it. See `CLK_SET_RATE_GATE` flag.
But I tend to agree, the better idiom is to `set_rate` we should do that
before `enable`. This will avoid any unintentional glitches on the clock
signal
