Commit 5e06aa50 authored by Chen-Yu Tsai's avatar Chen-Yu Tsai
Browse files

clk: sunxi-ng: sun50i: a64: Use sigma-delta modulation for audio PLL 



The audio blocks require specific clock rates. Until now we were using
the closest clock rate possible with integer N-M factors. This resulted
in audio playback being slightly slower than it should be.

The vendor kernel gets around this (for some SoCs) by using sigma-delta
modulation to generate a fractional-N factor. As the PLL hardware is
identical in most chips, we can port the settings for H3 onto the A64.

Acked-by: default avatarMaxime Ripard <maxime.ripard@bootlin.com>
Tested-by: default avatarVasily Khoruzhick <anarsoul@gmail.com>
Signed-off-by: default avatarChen-Yu Tsai <wens@csie.org>
parent ee678706

drivers/clk/sunxi-ng/ccu-sun50i-a64.c

+24 −13
Original line number Diff line number Diff line
@@ -51,15 +51,26 @@ static struct ccu_nkmp pll_cpux_clk = { 
 * the base (2x, 4x and 8x), and one variable divider (the one true

 * pll audio).

 *

 * We don't have any need for the variable divider for now, so we just

 * hardcode it to match with the clock names

 * With sigma-delta modulation for fractional-N on the audio PLL,

 * we have to use specific dividers. This means the variable divider

 * can no longer be used, as the audio codec requests the exact clock

 * rates we support through this mechanism. So we now hard code the

 * variable divider to 1. This means the clock rates will no longer

 * match the clock names.

 */

#define SUN50I_A64_PLL_AUDIO_REG	0x008



static SUNXI_CCU_NM_WITH_GATE_LOCK(pll_audio_base_clk, "pll-audio-base",

static struct ccu_sdm_setting pll_audio_sdm_table[] = {

	{ .rate = 22579200, .pattern = 0xc0010d84, .m = 8, .n = 7 },

	{ .rate = 24576000, .pattern = 0xc000ac02, .m = 14, .n = 14 },

};



static SUNXI_CCU_NM_WITH_SDM_GATE_LOCK(pll_audio_base_clk, "pll-audio-base",

				       "osc24M", 0x008,

				       8, 7,	/* N */

				       0, 5,	/* M */

				       pll_audio_sdm_table, BIT(24),

				       0x284, BIT(31),

				       BIT(31),	/* gate */

				       BIT(28),	/* lock */

				       CLK_SET_RATE_UNGATE);
@@ -594,9 +605,9 @@ static SUNXI_CCU_M_WITH_GATE(gpu_clk, "gpu", "pll-gpu", 
/* Fixed Factor clocks */

static CLK_FIXED_FACTOR(osc12M_clk, "osc12M", "osc24M", 2, 1, 0);



/* We hardcode the divider to 4 for now */

/* We hardcode the divider to 1 for now */

static CLK_FIXED_FACTOR(pll_audio_clk, "pll-audio",

			"pll-audio-base", 4, 1, CLK_SET_RATE_PARENT);

			"pll-audio-base", 1, 1, CLK_SET_RATE_PARENT);

static CLK_FIXED_FACTOR(pll_audio_2x_clk, "pll-audio-2x",

			"pll-audio-base", 2, 1, CLK_SET_RATE_PARENT);

static CLK_FIXED_FACTOR(pll_audio_4x_clk, "pll-audio-4x",
@@ -916,10 +927,10 @@ static int sun50i_a64_ccu_probe(struct platform_device *pdev) 
	if (IS_ERR(reg))

		return PTR_ERR(reg);



	/* Force the PLL-Audio-1x divider to 4 */

	/* Force the PLL-Audio-1x divider to 1 */

	val = readl(reg + SUN50I_A64_PLL_AUDIO_REG);

	val &= ~GENMASK(19, 16);

	writel(val | (3 << 16), reg + SUN50I_A64_PLL_AUDIO_REG);

	writel(val | (0 << 16), reg + SUN50I_A64_PLL_AUDIO_REG);



	writel(0x515, reg + SUN50I_A64_PLL_MIPI_REG);

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