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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: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
hifive-unleashed-5.1
Chen-Yu Tsai 2017-10-12 16:37:02 +08:00 committed by Maxime Ripard
parent a5e3e2b2ef
commit de34485191
1 changed files with 20 additions and 6 deletions
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26
drivers/clk/sunxi-ng/ccu-sun4i-a10.c
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@ -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 /