[PATCH] clk: Handle CLK_GET_RATE_NOCACHE flag in clk_set_rate()

[PATCH] clk: Handle CLK_GET_RATE_NOCACHE flag in clk_set_rate()

[Sylwester Nawrocki]

If a clock has CLK_GET_RATE_NOCACHE flag set the rate needs to
be recalculated, rather than referencing the cached value.

Currently cached clk->rate is compared with new value to see if
anything needs to be done in clk_set_rate(). This may cause required
clock controller registers update to not happen when same clock
frequency value is being set subsequently.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
---
 drivers/clk/clk.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 1144e8c..ffa304e 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1215,6 +1215,9 @@ int clk_set_rate(struct clk *clk, unsigned long rate)
 	/* prevent racing with updates to the clock topology */
 	clk_prepare_lock();

+	if (clk->flags & CLK_GET_RATE_NOCACHE)
+		__clk_recalc_rates(clk, 0);
+
 	/* bail early if nothing to do */
 	if (rate == clk->rate)
 		goto out;
--
1.7.9.5

Re: [PATCH] clk: Handle CLK_GET_RATE_NOCACHE flag in clk_set_rate()

[Sylwester Nawrocki]

On 06/21/2013 06:16 PM, Mike Turquette wrote:
> Quoting Sylwester Nawrocki (2013-06-21 06:07:35)
>> > If a clock has CLK_GET_RATE_NOCACHE flag set the rate needs to
>> > be recalculated, rather than referencing the cached value.
>> > 
>> > Currently cached clk->rate is compared with new value to see if
>> > anything needs to be done in clk_set_rate(). This may cause required
>> > clock controller registers update to not happen when same clock
>> > frequency value is being set subsequently.
>> > 
>> > Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
>> > Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
>
> Peter already sent a patch for this:
> https://git.linaro.org/gitweb?p=people/mturquette/linux.git;a=commitdiff;h=34e452a152efd25d654b7bc809df429337115b03

Thanks Mike, that also helps. My apologies for not having
it noticed earlier. I'm going to post a patch for the Exynos
clock driver, which adds missing CLK_GET_RATE_NOCACHE flags to
the ISP clock group and would be really effective together
with the above one.

Thanks,
Sylwester