This is a note to let you know that I've just added the patch titled
clk: sunxi-ng: sun4i: Set VCO and PLL bias current to lowest setting
to the 4.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
clk-sunxi-ng-sun4i-set-vco-and-pll-bias-current-to-lowest-setting.patch
and it can be found in the queue-4.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 80a6ec7d5e1653208eb53f6738620dab98f6f50e Mon Sep 17 00:00:00 2001
From: Chen-Yu Tsai <wens@xxxxxxxx>
Date: Thu, 6 Sep 2018 21:25:37 +0800
Subject: clk: sunxi-ng: sun4i: Set VCO and PLL bias current to lowest setting
From: Chen-Yu Tsai <wens@xxxxxxxx>
commit 80a6ec7d5e1653208eb53f6738620dab98f6f50e upstream.
The default mid-level PLL bias current setting interferes with sigma
delta modulation. This manifests as decreased audio quality at lower
sampling rates, which sounds like radio broadcast quality, and
distortion noises at sampling rates at 48 kHz or above.
Changing the bias current settings to the lowest gets rid of the
noise.
Fixes: de3448519194 ("clk: sunxi-ng: sun4i: Use sigma-delta modulation
for audio PLL")
Cc: <stable@xxxxxxxxxxxxxxx> # 4.15.x
Signed-off-by: Chen-Yu Tsai <wens@xxxxxxxx>
Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/clk/sunxi-ng/ccu-sun4i-a10.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
--- a/drivers/clk/sunxi-ng/ccu-sun4i-a10.c
+++ b/drivers/clk/sunxi-ng/ccu-sun4i-a10.c
@@ -1434,8 +1434,16 @@ static void __init sun4i_ccu_init(struct
return;
}
- /* Force the PLL-Audio-1x divider to 1 */
val = readl(reg + SUN4I_PLL_AUDIO_REG);
+
+ /*
+ * Force VCO and PLL bias current to lowest setting. Higher
+ * settings interfere with sigma-delta modulation and result
+ * in audible noise and distortions when using SPDIF or I2S.
+ */
+ val &= ~GENMASK(25, 16);
+
+ /* Force the PLL-Audio-1x divider to 1 */
val &= ~GENMASK(29, 26);
writel(val | (1 << 26), reg + SUN4I_PLL_AUDIO_REG);
Patches currently in stable-queue which might be from wens@xxxxxxxx are
queue-4.18/clk-sunxi-ng-sun4i-set-vco-and-pll-bias-current-to-lowest-setting.patch
