[RFC PATCH 4/4] ARM: dt: Add TWD bindings and driver support
Marc Zyngier
marc.zyngier at arm.com
Mon Jun 27 20:39:59 EST 2011
On 26/06/11 09:09, Grant Likely wrote:
> On Fri, Jun 24, 2011 at 03:10:59PM +0100, Marc Zyngier wrote:
>> Add device tree support to the arm_smp_twd driver.
>>
>> The DT bindings for the TWD are defined as such:
>> - one timer node per CPU, using corresponding PPI
>> interrupt controller
>> - provides both timer and watchdog interrupt
>>
>> Tested on RealView PB11MPCore and VExpress.
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
>> ---
>> Documentation/devicetree/bindings/arm/twd.txt | 54 ++++++++++++++
>> drivers/clocksource/arm_smp_twd.c | 92 +++++++++++++++++++++---
>> 2 files changed, 134 insertions(+), 12 deletions(-)
>> create mode 100644 Documentation/devicetree/bindings/arm/twd.txt
>>
>> diff --git a/Documentation/devicetree/bindings/arm/twd.txt b/Documentation/devicetree/bindings/arm/twd.txt
>> new file mode 100644
>> index 0000000..3823a81
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/arm/twd.txt
>> @@ -0,0 +1,54 @@
>> +* ARM Timer Watchdog
>> +
>> +ARM SMP cores are often associated with a TWD providing a per-cpu timer
>> +and a per-cpu watchdog. Usually wired to the PPI interface of a GIC.
>> +
>> +Main node properties:
>> +
>> +- compatible : "arm,smp-twd", "localtimer"
>
> "localtimer" isn't a very good compatible value. Compatible is
> intended to identify the specific hardware, and "localtimer" is a very
> generic name.
This is the early_device class name creeping in. I usually used the
"device_type" property, but been told this wasn't the right way...
Of course, if we get rid of the idea of early devices, this is a moot point.
> Also, as commented on for the gic, I'd like to see some level of
> versioning on the arm,smp-twd string.
There's only one version of TWD at the moment, so I guess I'll tie it to
the CPU core implementation, e.g: "arm,twd-11mpcore", "arm,twd-cortex-a9"...
>> +- reg : register mapping for the registers.
>> +- #address-cells : <1>
>> +- #size-cells : <0>
>> +
>> +Timer sub nodes (one per CPU)
>> +
>> +- interrupt-parent : phandle to the corresponding gic-ppi.
>> +- interrupts : <IRQtimer IRQwatchdog> (usually <29 30>)
>> +- reg : index of the CPU this timer is connected to.
>> +
>> +Example (ARM RealView PB11-MPCore):
>> +
>> +localtimer at 1f000600 {
>> + compatible = "arm,smp-twd", "localtimer";
>> + reg = <0x1f000600 0x100>;
>> + #address-cells = <1>;
>> + #size-cells = <0>;
>> +
>> + /*
>> + * One timer per CPU, bound to the corresponding
>> + * PPI interface.
>> + */
>> + timer at 0 {
>> + interrupt-parent = <&gic0ppi0>;
>> + interrupts = <29 30>;
>> + reg = <0>;
>> + };
>> +
>> + timer at 1 {
>> + interrupt-parent = <&gic0ppi1>;
>> + interrupts = <29 30>;
>> + reg = <1>;
>> + };
>> +
>> + timer at 2 {
>> + interrupt-parent = <&gic0ppi2>;
>> + interrupts = <29 30>;
>> + reg = <2>;
>> + };
>> +
>> + timer at 3 {
>> + interrupt-parent = <&gic0ppi3>;
>> + interrupts = <29 30>;
>> + reg = <3>;
>> + };
>> +};
>> diff --git a/drivers/clocksource/arm_smp_twd.c b/drivers/clocksource/arm_smp_twd.c
>> index 65f4669..586acad 100644
>> --- a/drivers/clocksource/arm_smp_twd.c
>> +++ b/drivers/clocksource/arm_smp_twd.c
>> @@ -19,6 +19,9 @@
>> #include <linux/interrupt.h>
>> #include <linux/ioport.h>
>> #include <linux/platform_device.h>
>> +#include <linux/of_platform.h>
>> +#include <linux/of_address.h>
>> +#include <linux/of_irq.h>
>> #include <linux/clk.h>
>> #include <linux/cpufreq.h>
>> #include <linux/err.h>
>> @@ -37,11 +40,11 @@
>> #define TWD_TIMER_CONTROL_IT_ENABLE (1 << 2)
>>
>> static void __iomem *twd_base;
>> -static int twd_ppi;
>>
>> static struct clk *twd_clk;
>> static unsigned long twd_timer_rate;
>> static DEFINE_PER_CPU(bool, irq_reqd);
>> +static DEFINE_PER_CPU(int, twd_irq);
>> static struct clock_event_device __percpu *twd_evt;
>>
>> static void twd_set_mode(enum clock_event_mode mode,
>> @@ -223,7 +226,7 @@ static void __cpuinit twd_setup(void *data)
>> clk->rating = 450;
>> clk->set_mode = twd_set_mode;
>> clk->set_next_event = twd_set_next_event;
>> - clk->irq = gic_ppi_to_vppi(twd_ppi);
>> + clk->irq = __get_cpu_var(twd_irq);
>> clk->cpumask = cpumask_of(smp_processor_id());
>>
>> pr_debug("Configuring %s on cpu #%d\n", clk->name, smp_processor_id());
>> @@ -290,31 +293,90 @@ static struct notifier_block __cpuinitdata twd_cpu_nb = {
>> .notifier_call = twd_cpu_notify,
>> };
>>
>> -static int twd_probe(struct platform_device *pdev)
>> +#ifdef CONFIG_OF
>> +static struct device_node *twd_get_timer_node(struct device_node *twd_np,
>> + struct device_node *child,
>> + int *timer_nr)
>> +{
>> + child = of_get_next_child(twd_np, child);
>> + if (child) {
>> + const __be32 *reg;
>> + reg = of_get_property(child, "reg", NULL);
>> + if (!reg)
>> + *timer_nr = -1;
>> + else
>> + *timer_nr = be32_to_cpu(*reg);
>
> There's a new function that should be done and merged in time for
> v3.1 that will help with reading properties. Keep an eye out for
> of_getprop_u32()
Yup, spotted. Will use it as soon as it appears in a tree nearby.
M.
--
Jazz is not dead. It just smells funny...
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