lkml.org 
[lkml]   [2018]   [Feb]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/3] clk: exynos5433: Allow audio subsystem clock rate propagation
Hi Sylwester,

On 2018년 02월 08일 00:18, Sylwester Nawrocki wrote:
> Hi Chanwoo,
>
> On 02/06/2018 05:06 AM, Chanwoo Choi wrote:
>>> drivers/clk/samsung/clk-exynos5433.c | 22 +++++++++++-----------
>>> 1 file changed, 11 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/drivers/clk/samsung/clk-exynos5433.c b/drivers/clk/samsung/clk-exynos5433.c
>>> index 74b70ddab4d6..d74361736e64 100644
>>> --- a/drivers/clk/samsung/clk-exynos5433.c
>>> +++ b/drivers/clk/samsung/clk-exynos5433.c
>>> @@ -246,14 +246,14 @@ static const struct samsung_fixed_rate_clock top_fixed_clks[] __initconst = {
>>>
>>> static const struct samsung_mux_clock top_mux_clks[] __initconst = {
>>> /* MUX_SEL_TOP0 */
>>> - MUX(CLK_MOUT_AUD_PLL, "mout_aud_pll", mout_aud_pll_p, MUX_SEL_TOP0,
>>> - 4, 1),
>>> + MUX_F(CLK_MOUT_AUD_PLL, "mout_aud_pll", mout_aud_pll_p, MUX_SEL_TOP0,
>>> + 4, 1, CLK_SET_RATE_PARENT, 0),
>>
>> If you add CLK_SET_RATE_PARENT to 'mout_aud_pll' and mout_aud_pll changes the rate,
>> fout_aud_pll's rate will be changed. But, fout_aud_pll is also the parent
>> of 'mout_aud_pll_user'. It might change the rate of children of mout_aud_pll_user.
>> mout_aud_pll_user would not want to change the parent's clock.
>>
>> fout_aud_pll 2 2 196608009 0 0
>> mout_aud_pll_user 1 1 196608009 0 0
>> mout_aud_pll 0 0 196608009 0 0
>
> I'd say the range of changes is such that the consumers of the affected child
> clocks can cope and could adjust to the changed frequencies. Those consumer
> devices are all components/peripherals of the audio subsystem (LPASS) and,

The mout_aud_pll_user has the child clock of serial_3.
serial_3 was used for bluetooth on TM2. If you change the aud_pll
with CLK_SET_RATE_PARENT, it might affect the bluetooth operation.
The bluetooth is only used for transfering the data.

Actually, I'm not sure that this patch might affect bluetooth operation or not.

> for example, in case of TM2 there is no issues at all with varying the AUD PLL
> frequency depending on the HDMI audio sample rate. The other audio path uses
> the audio CODEC's internal PLL as the root clock source. The AUD PLL frequency
> will need to be adjusted somehow anyway, we could also get the PLL clock
> directly and set it's rate, instead of relying on that rate propagation
> algorithm. I think we could also export a function from the exynos-lpass mfd
> driver for setting the PLL's rate directly, after listing the AUD PLL clock
> in the lpass DT node. That would be more flexible API, easier to adopt for
> various use cases/boards, now we have only TM2. I can't list the PLL clock
> in the sound node, that would not have passed the DT maintainters' review.
>

--
Best Regards,
Chanwoo Choi
Samsung Electronics

\
 
 \ /
  Last update: 2018-02-09 08:37    [W:0.087 / U:3.376 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site