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SubjectRe: [PATCH 2/3] clk: exynos5433: Allow audio subsystem clock rate propagation
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Hi Chanwoo,

On 02/09/2018 08:36 AM, Chanwoo Choi wrote:
> On 2018년 02월 08일 00:18, Sylwester Nawrocki wrote:
>> 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.

You are right, the AUD PLL frequency adjustments would break the bluetooth's
operation. I double checked and in the downstream kernel only one AUD PLL
frequency can be set - 196608009. So I will drop this patch and add just
a single PLL_36XX_RATE() entry for that frequency, the PMS values have been
confirmed by the HW team. Only 48000/9600/192000 sample rates will then be
supported natively and others could be through software rate conversion.

--
Regards,
Sylwester

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