[PATCH 1/2] clk: rockchip: add I2S internal clock IDs for rk3288
From: heiko@sntech.de (Heiko Stuebner)
Date: 2016-09-07 17:58:45
Also in:
linux-clk, linux-devicetree, linux-rockchip, lkml
Hi John, Am Mittwoch, 7. September 2016, 17:53:29 CEST schrieb John Keeping:
To minimize jitter on the I2S clocks, it is important that the denominator in the fractional divider is much greater than the numerator. Add identifiers for these internal clocks so that the specific clock topology and rates can be specified in the device tree.
The TRM states that the denominator must be bigger than 20. Is this the one you found or did you find further constraints? Did you try teaching the fractional divider to handle these constraints before going this way? Exporting the internal clocks really would be sort of plan d or e, after handling this in the clock framework failed. Especially as i2s rates are probably dependant on the media being handled (frequencies and such), so setting fractional rates statically in the dts won't help you much in the general case, as any new playback could trigger a clk_set_rate call anyway? Heiko
quoted hunk ↗ jump to hunk
Signed-off-by: John Keeping <redacted> --- include/dt-bindings/clock/rk3288-cru.h | 3 +++ 1 file changed, 3 insertions(+)diff --git a/include/dt-bindings/clock/rk3288-cru.hb/include/dt-bindings/clock/rk3288-cru.h index 9a586e2d9c91..9526653383d9 100644--- a/include/dt-bindings/clock/rk3288-cru.h +++ b/include/dt-bindings/clock/rk3288-cru.h@@ -88,6 +88,9 @@ #define SCLK_PVTM_GPU 124 #define SCLK_CRYPTO 125 #define SCLK_MIPIDSI_24M 126 +#define SCLK_I2S_PRE 127 +#define SCLK_I2S_SRC 128 +#define SCLK_I2S_FRAC 129 #define SCLK_MAC 151 #define SCLK_MACREF_OUT 152