[PATCH] ARM: dts: dra7: Correct clock tree for sys_32k_ck

[PATCH] ARM: dts: dra7: Correct clock tree for sys_32k_ck

[Keerthy]

This is w.r.t J6/J6eco: 32clk is pseudo (erratum i856) - clock source.
Errata i856 for the AM572x (DRA7xx) points out that the 32.768KHz external
crystal is not enabled at power up. Instead the CPU falls back to using
an emulation for the 32KHz clock which is SYSCLK1/610.  SYSCLK1 is usually
20MHz on boards so far (which gives an emulated frequency of 32.786KHz)

Modelling the same in device tree.

Signed-off-by: Keerthy <j-keerthy@ti.com>
---
Errata Document: http://www.ti.com/lit/er/sprz429h/sprz429h.pdf
Errata number: i856

Tested the debugfs clock tree nodes on DRA7-EVM.

 arch/arm/boot/dts/dra7xx-clocks.dtsi | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/arch/arm/boot/dts/dra7xx-clocks.dtsi b/arch/arm/boot/dts/dra7xx-clocks.dtsi
index 357bede..7f1f892 100644
--- a/arch/arm/boot/dts/dra7xx-clocks.dtsi
+++ b/arch/arm/boot/dts/dra7xx-clocks.dtsi
@@ -98,12 +98,20 @@
 		clock-frequency = <32768>;
 	};
 
-	sys_32k_ck: sys_32k_ck {
+	sys_clk32_crystal_ck: sys_clk32_crystal_ck {
 		#clock-cells = <0>;
 		compatible = "fixed-clock";
 		clock-frequency = <32768>;
 	};
 
+	sys_clk32_pseudo_ck: sys_clk32_pseudo_ck {
+		#clock-cells = <0>;
+		compatible = "fixed-factor-clock";
+		clocks = <&sys_clkin1>;
+		clock-mult = <1>;
+		clock-div = <610>;
+	};
+
 	virt_12000000_ck: virt_12000000_ck {
 		#clock-cells = <0>;
 		compatible = "fixed-clock";
@@ -2146,4 +2154,12 @@
 		ti,bit-shift = <0>;
 		reg = <0x558>;
 	};
+
+	sys_32k_ck: sys_32k_ck {
+		#clock-cells = <0>;
+		compatible = "ti,mux-clock";
+		clocks = <&sys_clk32_crystal_ck>, <&sys_clk32_pseudo_ck>, <&sys_clk32_pseudo_ck>, <&sys_clk32_pseudo_ck>;
+		ti,bit-shift = <8>;
+		reg = <0x6c4>;
+	};
 };
-- 
1.9.1

Re: [PATCH] ARM: dts: dra7: Correct clock tree for sys_32k_ck

[Keerthy]

On Monday 14 March 2016 05:29 PM, Keerthy wrote:
> This is w.r.t J6/J6eco: 32clk is pseudo (erratum i856) - clock source.
> Errata i856 for the AM572x (DRA7xx) points out that the 32.768KHz external
> crystal is not enabled at power up. Instead the CPU falls back to using
> an emulation for the 32KHz clock which is SYSCLK1/610.  SYSCLK1 is usually
> 20MHz on boards so far (which gives an emulated frequency of 32.786KHz)

Missing signed-off. Please ignore this patch.

>
> Modelling the same in device tree.
>
> Signed-off-by: Keerthy <j-keerthy@ti.com>
> ---
> Errata Document: http://www.ti.com/lit/er/sprz429h/sprz429h.pdf
> Errata number: i856
>
> Tested the debugfs clock tree nodes on DRA7-EVM.
>
>   arch/arm/boot/dts/dra7xx-clocks.dtsi | 18 +++++++++++++++++-
>   1 file changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/boot/dts/dra7xx-clocks.dtsi b/arch/arm/boot/dts/dra7xx-clocks.dtsi
> index 357bede..7f1f892 100644
> --- a/arch/arm/boot/dts/dra7xx-clocks.dtsi
> +++ b/arch/arm/boot/dts/dra7xx-clocks.dtsi
> @@ -98,12 +98,20 @@
>   		clock-frequency = <32768>;
>   	};
>
> -	sys_32k_ck: sys_32k_ck {
> +	sys_clk32_crystal_ck: sys_clk32_crystal_ck {
>   		#clock-cells = <0>;
>   		compatible = "fixed-clock";
>   		clock-frequency = <32768>;
>   	};
>
> +	sys_clk32_pseudo_ck: sys_clk32_pseudo_ck {
> +		#clock-cells = <0>;
> +		compatible = "fixed-factor-clock";
> +		clocks = <&sys_clkin1>;
> +		clock-mult = <1>;
> +		clock-div = <610>;
> +	};
> +
>   	virt_12000000_ck: virt_12000000_ck {
>   		#clock-cells = <0>;
>   		compatible = "fixed-clock";
> @@ -2146,4 +2154,12 @@
>   		ti,bit-shift = <0>;
>   		reg = <0x558>;
>   	};
> +
> +	sys_32k_ck: sys_32k_ck {
> +		#clock-cells = <0>;
> +		compatible = "ti,mux-clock";
> +		clocks = <&sys_clk32_crystal_ck>, <&sys_clk32_pseudo_ck>, <&sys_clk32_pseudo_ck>, <&sys_clk32_pseudo_ck>;
> +		ti,bit-shift = <8>;
> +		reg = <0x6c4>;
> +	};
>   };
>