Thread (5 messages) 5 messages, 3 authors, 2020-08-25
STALE2131d LANDED

[PATCH] clk: sunxi-ng: sun8i: r40: Use sigma delta modulation for audio PLL

From: Jernej Skrabec <hidden>
Date: 2020-08-25 13:11:19
Also in: linux-clk, lkml
Subsystem: arm/allwinner sunxi soc support, common clk framework, the rest · Maintainers: Chen-Yu Tsai, Jernej Skrabec, Samuel Holland, Michael Turquette, Stephen Boyd, Linus Torvalds

Audio cores need specific clock rates which can't be simply obtained by
adjusting integer multipliers and dividers. HW for such cases supports
delta-sigma modulation which enables fractional multipliers.

Port H3 delta-sigma table to R40. They have identical audio PLLs.

Signed-off-by: Jernej Skrabec <redacted>
---
 drivers/clk/sunxi-ng/ccu-sun8i-r40.c | 37 ++++++++++++++++++----------
 1 file changed, 24 insertions(+), 13 deletions(-)
diff --git a/drivers/clk/sunxi-ng/ccu-sun8i-r40.c b/drivers/clk/sunxi-ng/ccu-sun8i-r40.c
index 23bfe1d12f21..84153418453f 100644
--- a/drivers/clk/sunxi-ng/ccu-sun8i-r40.c
+++ b/drivers/clk/sunxi-ng/ccu-sun8i-r40.c
@@ -45,18 +45,29 @@ static struct ccu_nkmp pll_cpu_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_R40_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_MIN_MAX(pll_video0_clk, "pll-video0",
 						"osc24M", 0x0010,
@@ -952,10 +963,10 @@ static const struct clk_hw *clk_parent_pll_audio[] = {
 	&pll_audio_base_clk.common.hw
 };
 
-/* We hardcode the divider to 4 for now */
+/* We hardcode the divider to 1 for now */
 static CLK_FIXED_FACTOR_HWS(pll_audio_clk, "pll-audio",
 			    clk_parent_pll_audio,
-			    4, 1, CLK_SET_RATE_PARENT);
+			    1, 1, CLK_SET_RATE_PARENT);
 static CLK_FIXED_FACTOR_HWS(pll_audio_2x_clk, "pll-audio-2x",
 			    clk_parent_pll_audio,
 			    2, 1, CLK_SET_RATE_PARENT);
@@ -1307,10 +1318,10 @@ static int sun8i_r40_ccu_probe(struct platform_device *pdev)
 	if (IS_ERR(reg))
 		return PTR_ERR(reg);
 
-	/* Force the PLL-Audio-1x divider to 4 */
+	/* Force the PLL-Audio-1x divider to 1 */
 	val = readl(reg + SUN8I_R40_PLL_AUDIO_REG);
 	val &= ~GENMASK(19, 16);
-	writel(val | (3 << 16), reg + SUN8I_R40_PLL_AUDIO_REG);
+	writel(val | (0 << 16), reg + SUN8I_R40_PLL_AUDIO_REG);
 
 	/* Force PLL-MIPI to MIPI mode */
 	val = readl(reg + SUN8I_R40_PLL_MIPI_REG);
-- 
2.28.0


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
Keyboard shortcuts
hback out one level
jnext message in thread
kprevious message in thread
ldrill in
Escclose help / fold thread tree
?toggle this help