linux-kernel - Re: [linux-sunxi] [PATCH] clk: sunxi-ng: h6: Use sigma-delta modulation for audio PLL

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Message-ID: <8129141.yvSaxnLE4m@jernej-laptop>
Date:   Wed, 18 Sep 2019 07:21:00 +0200
From:   Jernej Škrabec <jernej.skrabec@...l.net>
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     Maxime Ripard <mripard@...nel.org>,
        Mike Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [linux-sunxi] [PATCH] clk: sunxi-ng: h6: Use sigma-delta modulation for audio PLL

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@...l.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@...l.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?

Best regards,
Jernej

> 
> ChenYu
> 
> > @@ -1215,12 +1224,12 @@ static int sun50i_h6_ccu_probe(struct
> > platform_device *pdev)> 
> >         }
> >         
> >         /*
> > 
> > -        * Force the post-divider of pll-audio to 8 and the output divider
> > -        * of it to 1, to make the clock name represents the real
> > frequency. +        * Force the post-divider of pll-audio to 12 and the
> > output divider +        * of it to 2, so 24576000 and 22579200 rates can
> > be set exactly.> 
> >          */
> >         
> >         val = readl(reg + SUN50I_H6_PLL_AUDIO_REG);
> >         val &= ~(GENMASK(21, 16) | BIT(0));
> > 
> > -       writel(val | (7 << 16), reg + SUN50I_H6_PLL_AUDIO_REG);
> > +       writel(val | (11 << 16) | BIT(0), reg + SUN50I_H6_PLL_AUDIO_REG);
> > 
> >         /*
> >         
> >          * First clock parent (osc32K) is unusable for CEC. But since
> >          there
> > 
> > --
> > 2.23.0
> > 
> > --
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> > linux-sunxi+unsubscribe@...glegroups.com. To view this discussion on the
> > web, visit
> > https://groups.google.com/d/msgid/linux-sunxi/20190914135100.327412-1-jer
> > nej.skrabec%40siol.net.