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Commit de344851 authored by Chen-Yu Tsai's avatar Chen-Yu Tsai Committed by Maxime Ripard
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clk: sunxi-ng: sun4i: 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 newer SoCs) by using sigma-delta
modulation to generate a fractional-N factor. As the PLL hardware is
identical in most chips, we can back port the settings from the newer
SoC, in this case the H3, onto the A10 and A20.

Signed-off-by: default avatarChen-Yu Tsai <wens@csie.org>
Signed-off-by: default avatarMaxime Ripard <maxime.ripard@free-electrons.com>
parent a5e3e2b2

drivers/clk/sunxi-ng/ccu-sun4i-a10.c

+20 −6
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
#include "ccu_nkmp.h"

#include "ccu_nm.h"

#include "ccu_phase.h"

#include "ccu_sdm.h"



#include "ccu-sun4i-a10.h"
@@ -51,16 +52,29 @@ static struct ccu_nkmp pll_core_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 SUN4I_PLL_AUDIO_REG	0x008



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 struct ccu_nm pll_audio_base_clk = {

	.enable		= BIT(31),

	.n		= _SUNXI_CCU_MULT_OFFSET(8, 7, 0),

	.m		= _SUNXI_CCU_DIV_OFFSET(0, 5, 0),

	.sdm		= _SUNXI_CCU_SDM(pll_audio_sdm_table, 0,

					 0x00c, BIT(31)),

	.common		= {

		.reg		= 0x008,

		.features	= CCU_FEATURE_SIGMA_DELTA_MOD,

		.hw.init	= CLK_HW_INIT("pll-audio-base",

					      "hosc",

					      &ccu_nm_ops,
@@ -1021,9 +1035,9 @@ static struct ccu_common *sun4i_sun7i_ccu_clks[] = { 
	&out_b_clk.common

};



/* Post-divider for pll-audio is hardcoded to 4 */

/* Post-divider for pll-audio is hardcoded to 1 */

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",
@@ -1420,10 +1434,10 @@ static void __init sun4i_ccu_init(struct device_node *node, 
		return;

	}



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

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

	val = readl(reg + SUN4I_PLL_AUDIO_REG);

	val &= ~GENMASK(29, 26);

	writel(val | (4 << 26), reg + SUN4I_PLL_AUDIO_REG);

	writel(val | (1 << 26), reg + SUN4I_PLL_AUDIO_REG);



	/*

	 * Use the peripheral PLL6 as the AHB parent, instead of CPU /