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clk: sunxi-ng: sun6i: 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 A31.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
This commit is contained in:
Chen-Yu Tsai 2017-10-12 16:37:04 +08:00 committed by Maxime Ripard
parent 042f7f8f97
commit ee6501d692
1 changed files with 25 additions and 13 deletions
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38
drivers/clk/sunxi-ng/ccu-sun6i-a31.c
View File

@ -31,6 +31,7 @@
#include "ccu_nkmp.h"
#include "ccu_nm.h"
#include "ccu_phase.h"
#include "ccu_sdm.h"
#include "ccu-sun6i-a31.h"
@ -48,18 +49,29 @@ static SUNXI_CCU_NKM_WITH_GATE_LOCK(pll_cpu_clk, "pll-cpu",
* 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 SUN6I_A31_PLL_AUDIO_REG 0x008
static SUNXI_CCU_NM_WITH_GATE_LOCK(pll_audio_base_clk, "pll-audio-base",
"osc24M", 0x008,
8, 7, /* N */
0, 5, /* M */
BIT(31), /* gate */
BIT(28), /* lock */
CLK_SET_RATE_UNGATE);
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);
static SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK(pll_video0_clk, "pll-video0",
"osc24M", 0x010,
@ -950,9 +962,9 @@ static struct ccu_common *sun6i_a31_ccu_clks[] = {
&out_c_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",
@ -1221,10 +1233,10 @@ static void __init sun6i_a31_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 + SUN6I_A31_PLL_AUDIO_REG);
val &= ~GENMASK(19, 16);
writel(val | (3 << 16), reg + SUN6I_A31_PLL_AUDIO_REG);
writel(val | (0 << 16), reg + SUN6I_A31_PLL_AUDIO_REG);
/* Force PLL-MIPI to MIPI mode */
val = readl(reg + SUN6I_A31_PLL_MIPI_REG);