Allwinner has previously released a H616 audio driver which also
provides sigma-delta modulation for the audio PLL clocks. This approach
is used in other Allwinner SoCs, including the H3 and A64.
The manual-provided clock values are:
PLL_AUDIO(hs) = 24 MHz*N/M1
PLL_AUDIO(4X) = 24 MHz*N/M0/M1/P
PLL_AUDIO(2X) = 24 MHz*N/M0/M1/P/2
PLL_AUDIO(1X) = 24 MHz*N/M0/M1/P/4
A fixed post-divider of 2 is used to account for a M0 divider of
2, which cannot be modelled by the existing macros and ccu_nm struct.
Add SDM to the H616 clock control unit driver.
Signed-off-by: Ryan Walklin <ryan@xxxxxxxxxxxxx>
---
Changelog v1..v2:
- Add fixed_post_div to high-speed audio clock to correct M0 value to 1 (ie divide by 2) based on manual
- Correct PLL_AUDIO_(4/2/1)X clocks to manual-provided values
- Add/correct inline comments for the above.
- add CCU_FEATURE_FIXED_POSTDIV to pll_audio_hs_clk.common.features
Changelog v2..v3:
- Update comments and commit message to more accurately reflect SDM changes and rationale
---
drivers/clk/sunxi-ng/ccu-sun50i-h616.c | 46 +++++++++++++++++---------
1 file changed, 30 insertions(+), 16 deletions(-)
diff --git a/drivers/clk/sunxi-ng/ccu-sun50i-h616.c b/drivers/clk/sunxi-ng/ccu-sun50i-h616.c
index 6c7623d4c59ea..05727fa1ee46e 100644
--- a/drivers/clk/sunxi-ng/ccu-sun50i-h616.c
+++ b/drivers/clk/sunxi-ng/ccu-sun50i-h616.c
@@ -215,20 +215,30 @@ static struct ccu_nkmp pll_de_clk = {
},
};
-/*
- * TODO: Determine SDM settings for the audio PLL. The manual suggests
- * PLL_FACTOR_N=16, PLL_POST_DIV_P=2, OUTPUT_DIV=2, pattern=0xe000c49b
- * for 24.576 MHz, and PLL_FACTOR_N=22, PLL_POST_DIV_P=3, OUTPUT_DIV=2,
- * pattern=0xe001288c for 22.5792 MHz.
- * This clashes with our fixed PLL_POST_DIV_P.
+/*
+ * Sigma-delta modulation settings table obtained from the vendor SDK driver.
+ * There are additional M0 and M1 divider bits not modelled here, so forced to
+ * fixed values in the probe routine. Sigma-delta modulation allows providing a
+ * fractional-N divider in the PLL, to help reaching those specific
+ * frequencies with less error.
*/
+static struct ccu_sdm_setting pll_audio_sdm_table[] = {
+ { .rate = 90316800, .pattern = 0xc001288d, .m = 3, .n = 22 },
+ { .rate = 98304000, .pattern = 0xc001eb85, .m = 5, .n = 40 },
+};
+
#define SUN50I_H616_PLL_AUDIO_REG 0x078
static struct ccu_nm pll_audio_hs_clk = {
.enable = BIT(31),
.lock = BIT(28),
.n = _SUNXI_CCU_MULT_MIN(8, 8, 12),
- .m = _SUNXI_CCU_DIV(1, 1), /* input divider */
+ .m = _SUNXI_CCU_DIV(16, 6),
+ .sdm = _SUNXI_CCU_SDM(pll_audio_sdm_table,
+ BIT(24), 0x178, BIT(31)),
+ .fixed_post_div = 2,
.common = {
+ .features = CCU_FEATURE_FIXED_POSTDIV |
+ CCU_FEATURE_SIGMA_DELTA_MOD,
.reg = 0x078,
.hw.init = CLK_HW_INIT("pll-audio-hs", "osc24M",
&ccu_nm_ops,
@@ -701,18 +711,20 @@ static const struct clk_hw *clk_parent_pll_audio[] = {
};
/*
- * The divider of pll-audio is fixed to 24 for now, so 24576000 and 22579200
- * rates can be set exactly in conjunction with sigma-delta modulation.
+ * The PLL_AUDIO_4X clock defaults to 24.5714 MHz according to the manual, with
+ * a final divider of 1. The 2X and 1X clocks use 2 and 4 respectively. The 1x
+ * clock is set to either 24576000 or 22579200 for 48Khz and 44.1Khz (and
+ * multiples).
*/
static CLK_FIXED_FACTOR_HWS(pll_audio_1x_clk, "pll-audio-1x",
clk_parent_pll_audio,
- 96, 1, CLK_SET_RATE_PARENT);
+ 4, 1, CLK_SET_RATE_PARENT);
static CLK_FIXED_FACTOR_HWS(pll_audio_2x_clk, "pll-audio-2x",
clk_parent_pll_audio,
- 48, 1, CLK_SET_RATE_PARENT);
+ 2, 1, CLK_SET_RATE_PARENT);
static CLK_FIXED_FACTOR_HWS(pll_audio_4x_clk, "pll-audio-4x",
clk_parent_pll_audio,
- 24, 1, CLK_SET_RATE_PARENT);
+ 1, 1, CLK_SET_RATE_PARENT);
static const struct clk_hw *pll_periph0_parents[] = {
&pll_periph0_clk.common.hw
@@ -1162,12 +1174,14 @@ static int sun50i_h616_ccu_probe(struct platform_device *pdev)
}
/*
- * Force the post-divider of pll-audio to 12 and the output divider
- * of it to 2, so 24576000 and 22579200 rates can be set exactly.
+ * Set the output-divider for the pll-audio clocks (M0) to 2 and the
+ * input divider (M1) to 1 as recommended by the manual when using
+ * SDM.
*/
val = readl(reg + SUN50I_H616_PLL_AUDIO_REG);
- val &= ~(GENMASK(21, 16) | BIT(0));
- writel(val | (11 << 16) | BIT(0), reg + SUN50I_H616_PLL_AUDIO_REG);
+ val &= ~BIT(1);
+ val |= BIT(0);
+ writel(val, reg + SUN50I_H616_PLL_AUDIO_REG);
/*
* First clock parent (osc32K) is unusable for CEC. But since there
--
2.47.0
