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SubjectRe: [linux-sunxi] [PATCH] clk: sunxi-ng: h6: Use sigma-delta modulation for audio PLL
On Wed, Sep 18, 2019 at 1:21 PM Jernej Škrabec <jernej.skrabec@siol.net> wrote:
>
> Dne torek, 17. september 2019 ob 08:54:08 CEST je Chen-Yu Tsai napisal(a):
> > On Sat, Sep 14, 2019 at 9:51 PM Jernej Skrabec <jernej.skrabec@siol.net>
> wrote:
> > > Audio devices needs exact clock rates in order to correctly reproduce
> > > the sound. Until now, only integer factors were used to configure H6
> > > audio PLL which resulted in inexact rates. Fix that by adding support
> > > for fractional factors using sigma-delta modulation look-up table. It
> > > contains values for two most commonly used audio base frequencies.
> > >
> > > Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
> > > ---
> > >
> > > drivers/clk/sunxi-ng/ccu-sun50i-h6.c | 21 +++++++++++++++------
> > > 1 file changed, 15 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/drivers/clk/sunxi-ng/ccu-sun50i-h6.c
> > > b/drivers/clk/sunxi-ng/ccu-sun50i-h6.c index d89353a3cdec..ed6338d74474
> > > 100644
> > > --- a/drivers/clk/sunxi-ng/ccu-sun50i-h6.c
> > > +++ b/drivers/clk/sunxi-ng/ccu-sun50i-h6.c
> > > @@ -203,12 +203,21 @@ static struct ccu_nkmp pll_hsic_clk = {
> > >
> > > * hardcode it to match with the clock names.
> > > */
> > >
> > > #define SUN50I_H6_PLL_AUDIO_REG 0x078
> > >
> > > +
> > > +static struct ccu_sdm_setting pll_audio_sdm_table[] = {
> > > + { .rate = 541900800, .pattern = 0xc001288d, .m = 1, .n = 22 },
> > > + { .rate = 589824000, .pattern = 0xc00126e9, .m = 1, .n = 24 },
> > > +};
> > > +
> > >
> > > static struct ccu_nm pll_audio_base_clk = {
> > >
> > > .enable = BIT(31),
> > > .lock = BIT(28),
> > > .n = _SUNXI_CCU_MULT_MIN(8, 8, 12),
> > > .m = _SUNXI_CCU_DIV(1, 1), /* input divider */
> > >
> > > + .sdm = _SUNXI_CCU_SDM(pll_audio_sdm_table,
> > > + BIT(24), 0x178, BIT(31)),
> > >
> > > .common = {
> > >
> > > + .features = CCU_FEATURE_SIGMA_DELTA_MOD,
> > >
> > > .reg = 0x078,
> > > .hw.init = CLK_HW_INIT("pll-audio-base", "osc24M",
> > >
> > > &ccu_nm_ops,
> > >
> > > @@ -753,12 +762,12 @@ static const struct clk_hw *clk_parent_pll_audio[] =
> > > {>
> > > };
> > >
> > > /*
> > >
> > > - * The divider of pll-audio is fixed to 8 now, as pll-audio-4x has a
> > > - * fixed post-divider 2.
> > > + * The divider of pll-audio is fixed to 24 for now, so 24576000 and
> > > 22579200 + * rates can be set exactly in conjunction with sigma-delta
> > > modulation.>
> > > */
> > >
> > > static CLK_FIXED_FACTOR_HWS(pll_audio_clk, "pll-audio",
> > >
> > > clk_parent_pll_audio,
> > >
> > > - 8, 1, CLK_SET_RATE_PARENT);
> > > + 24, 1, CLK_SET_RATE_PARENT);
> > >
> > > static CLK_FIXED_FACTOR_HWS(pll_audio_2x_clk, "pll-audio-2x",
> > >
> > > clk_parent_pll_audio,
> > > 4, 1, CLK_SET_RATE_PARENT);
> >
> > You need to fix the factors for the other two outputs as well, since all
> > three are derived from pll-audio-base.
>
> Fix how? pll-audio-2x and pll-audio-4x clocks have fixed divider in regards to
> pll-audio-base, while pll-audio has not. Unless you mean changing their name?

Argh... I got it wrong. It looks good actually.

Acked-by: Chen-Yu Tsai <wens@csie.org>

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