[RFC,3/8] ARM: twd: clock rate from DT (if no DT clk tree)

Commit Message

Afzal Mohammed Feb. 18, 2013, 11:37 a.m. UTC

Add an optional property to find clock-frequency from DT. This helps
as a fallback mechanism in case there is no representation of clock
tree in DT.

Signed-off-by: Afzal Mohammed <[e-mail]>
---
 Documentation/devicetree/bindings/arm/twd.txt | 7 ++++++-
 arch/arm/kernel/smp_twd.c                     | 8 ++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

Comments

Santosh Shilimkar Feb. 19, 2013, 10:18 a.m. UTC | #1

On Monday 18 February 2013 05:07 PM, Afzal Mohammed wrote:
> Add an optional property to find clock-frequency from DT. This helps
> as a fallback mechanism in case there is no representation of clock
> tree in DT.
>
> Signed-off-by: Afzal Mohammed <[e-mail]>
> ---
This won't work always because twd clock is CPU dependent and changes
with CPU clock speed. And more importantly to get CPUFreq working, you
need to provide the correct clock-node to TWD library. Refer OMAP4 clock
data for reference.

Regards,
Santosh

Patch

diff --git a/Documentation/devicetree/bindings/arm/twd.txt b/Documentation/devicetree/bindings/arm/twd.txt
index 75b8610..fdafa4f 100644
--- a/Documentation/devicetree/bindings/arm/twd.txt
+++ b/Documentation/devicetree/bindings/arm/twd.txt
@@ -7,8 +7,9 @@  and watchdog.
 The TWD is usually attached to a GIC to deliver its two per-processor
 interrupts.
 
-** Timer node required properties:
+** Timer node properties:
 
+Required properties:
 - compatible : Should be one of:
 	"arm,cortex-a9-twd-timer"
 	"arm,cortex-a5-twd-timer"
@@ -19,12 +20,16 @@  interrupts.
 - reg : Specify the base address and the size of the TWD timer
 	register window.
 
+Optional property:
+- clock-frequency : frequency(Hz) of peripheral clock fed to timer
+
 Example:
 
 	twd-timer@2c000600 {
 		compatible = "arm,arm11mp-twd-timer"";
 		reg = <0x2c000600 0x20>;
 		interrupts = <1 13 0xf01>;
+		clock-frequency = <300000000>;
 	};
 
 ** Watchdog node properties:
diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
index 118f4f2..aac0f9f 100644
--- a/arch/arm/kernel/smp_twd.c
+++ b/arch/arm/kernel/smp_twd.c
@@ -247,7 +247,15 @@  static void twd_get_clock(struct device_node *np)
 		twd_clk = clk_get_sys("smp_twd", NULL);
 
 	if (IS_ERR(twd_clk)) {
+		u32 freq;
+
 		pr_err("smp_twd: clock not found %d\n", (int) PTR_ERR(twd_clk));
+
+		/* If there is no representation of clock tree in DT,
+		   provide a fallback option to obtain frequency
+		 */
+		if (np && !of_property_read_u32(np, "clock-frequency", &freq))
+			twd_timer_rate = freq;
 		return;
 	}