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clk: sunxi-ng: a33: 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 A33.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
This commit is contained in:
Chen-Yu Tsai 2018-12-05 18:11:50 +08:00 committed by Maxime Ripard
parent 64f28430cf
commit 37bb18398a
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GPG Key ID: E3EF0D6F671851C5
1 changed files with 24 additions and 13 deletions
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25
drivers/clk/sunxi-ng/ccu-sun8i-a33.c
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@ -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 SUN8I_A33_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);
@ -576,9 +587,9 @@ static struct ccu_common *sun8i_a33_ccu_clks[] = {
&ats_clk.common,
};
/* 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",
@ -781,10 +792,10 @@ static void __init sun8i_a33_ccu_setup(struct device_node *node)
return;
}
/* Force the PLL-Audio-1x divider to 4 */
/* Force the PLL-Audio-1x divider to 1 */
val = readl(reg + SUN8I_A33_PLL_AUDIO_REG);
val &= ~GENMASK(19, 16);
writel(val | (3 << 16), reg + SUN8I_A33_PLL_AUDIO_REG);
writel(val | (0 << 16), reg + SUN8I_A33_PLL_AUDIO_REG);
/* Force PLL-MIPI to MIPI mode */
val = readl(reg + SUN8I_A33_PLL_MIPI_REG);