[RESEND,v2,4/6] clocksource: kona: Add basic use of external clock

Message ID 1381960030-1640-5-git-send-email-tim.kryger@linaro.org
State New
Headers show

Commit Message

Tim Kryger Oct. 16, 2013, 9:47 p.m.
When an clock handle is specified in the device tree, enable it and use
it to determine the external clock frequency.

Signed-off-by: Tim Kryger <tim.kryger@linaro.org>
Reviewed-by: Markus Mayer <markus.mayer@linaro.org>
Reviewed-by: Matt Porter <matt.porter@linaro.org>
---
 drivers/clocksource/bcm_kona_timer.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

Comments

Mark Rutland Oct. 17, 2013, 2:05 p.m. | #1
On Wed, Oct 16, 2013 at 10:47:08PM +0100, Tim Kryger wrote:
> When an clock handle is specified in the device tree, enable it and use
> it to determine the external clock frequency.

I'd drop handle here and just say "When a clock is specified".

This will need a binding document update.

> 
> Signed-off-by: Tim Kryger <tim.kryger@linaro.org>
> Reviewed-by: Markus Mayer <markus.mayer@linaro.org>
> Reviewed-by: Matt Porter <matt.porter@linaro.org>
> ---
>  drivers/clocksource/bcm_kona_timer.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/clocksource/bcm_kona_timer.c b/drivers/clocksource/bcm_kona_timer.c
> index 0d7d8c3..fd11f96 100644
> --- a/drivers/clocksource/bcm_kona_timer.c
> +++ b/drivers/clocksource/bcm_kona_timer.c
> @@ -17,6 +17,7 @@
>  #include <linux/jiffies.h>
>  #include <linux/clockchips.h>
>  #include <linux/types.h>
> +#include <linux/clk.h>
>  
>  #include <linux/io.h>
>  #include <asm/mach/time.h>
> @@ -107,11 +108,18 @@ static const struct of_device_id bcm_timer_ids[] __initconst = {
>  static void __init kona_timers_init(struct device_node *node)
>  {
>  	u32 freq;
> +	struct clk *external_clk;
>  
> -	if (!of_property_read_u32(node, "clock-frequency", &freq))
> +	external_clk = of_clk_get_by_name(node, NULL);

Is there only a single external clock input to the kona timer, or is
only one relevant here?

Are there any other inputs currently not modelled (e.g. regulators)?

> +
> +	if (!IS_ERR(external_clk)) {
> +		arch_timer_rate = clk_get_rate(external_clk);
> +		clk_prepare_enable(external_clk);
> +	} else if (!of_property_read_u32(node, "clock-frequency", &freq)) {
>  		arch_timer_rate = freq;
> -	else
> -		panic("clock-frequency not set in the .dts file");
> +	} else {
> +		panic("neither clock-frequency or clocks handle in .dts file");

Nit: it's not a handle, it's a phandle+args pair.

Why not just "Unable to determine clock frequency"?

Do we need to panic here? Might a system have other clocks it could use
to continue?

Thanks,
Mark.
Tim Kryger Oct. 21, 2013, 9:07 p.m. | #2
On Thu, Oct 17, 2013 at 7:05 AM, Mark Rutland <mark.rutland@arm.com> wrote:
> On Wed, Oct 16, 2013 at 10:47:08PM +0100, Tim Kryger wrote:
>> When an clock handle is specified in the device tree, enable it and use
>> it to determine the external clock frequency.
>
> I'd drop handle here and just say "When a clock is specified".
>
> This will need a binding document update.

Can you be more specific about what you are looking for here?

Shall I just say that the frequency property is now deprecated since
it actually belongs to the external clock whose association with a
kona timer instance might be declared in the DT using the common clock
bindings but could also be declared through other means?

>> Signed-off-by: Tim Kryger <tim.kryger@linaro.org>
>> Reviewed-by: Markus Mayer <markus.mayer@linaro.org>
>> Reviewed-by: Matt Porter <matt.porter@linaro.org>
>> ---
>>  drivers/clocksource/bcm_kona_timer.c | 14 +++++++++++---
>>  1 file changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/clocksource/bcm_kona_timer.c b/drivers/clocksource/bcm_kona_timer.c
>> index 0d7d8c3..fd11f96 100644
>> --- a/drivers/clocksource/bcm_kona_timer.c
>> +++ b/drivers/clocksource/bcm_kona_timer.c
>> @@ -17,6 +17,7 @@
>>  #include <linux/jiffies.h>
>>  #include <linux/clockchips.h>
>>  #include <linux/types.h>
>> +#include <linux/clk.h>
>>
>>  #include <linux/io.h>
>>  #include <asm/mach/time.h>
>> @@ -107,11 +108,18 @@ static const struct of_device_id bcm_timer_ids[] __initconst = {
>>  static void __init kona_timers_init(struct device_node *node)
>>  {
>>       u32 freq;
>> +     struct clk *external_clk;
>>
>> -     if (!of_property_read_u32(node, "clock-frequency", &freq))
>> +     external_clk = of_clk_get_by_name(node, NULL);
>
> Is there only a single external clock input to the kona timer, or is
> only one relevant here?
>
> Are there any other inputs currently not modelled (e.g. regulators)?

The timer block relies upon a single clock and does not use any regulators.

>> +
>> +     if (!IS_ERR(external_clk)) {
>> +             arch_timer_rate = clk_get_rate(external_clk);
>> +             clk_prepare_enable(external_clk);
>> +     } else if (!of_property_read_u32(node, "clock-frequency", &freq)) {
>>               arch_timer_rate = freq;
>> -     else
>> -             panic("clock-frequency not set in the .dts file");
>> +     } else {
>> +             panic("neither clock-frequency or clocks handle in .dts file");
>
> Nit: it's not a handle, it's a phandle+args pair.
>
> Why not just "Unable to determine clock frequency"?

Sure that sounds fine.

>
> Do we need to panic here? Might a system have other clocks it could use
> to continue?

I completely agree that this driver could be improved.  However, this
is unrelated to the topic of this series so I will address it later in
a separate patch.

Patch

diff --git a/drivers/clocksource/bcm_kona_timer.c b/drivers/clocksource/bcm_kona_timer.c
index 0d7d8c3..fd11f96 100644
--- a/drivers/clocksource/bcm_kona_timer.c
+++ b/drivers/clocksource/bcm_kona_timer.c
@@ -17,6 +17,7 @@ 
 #include <linux/jiffies.h>
 #include <linux/clockchips.h>
 #include <linux/types.h>
+#include <linux/clk.h>
 
 #include <linux/io.h>
 #include <asm/mach/time.h>
@@ -107,11 +108,18 @@  static const struct of_device_id bcm_timer_ids[] __initconst = {
 static void __init kona_timers_init(struct device_node *node)
 {
 	u32 freq;
+	struct clk *external_clk;
 
-	if (!of_property_read_u32(node, "clock-frequency", &freq))
+	external_clk = of_clk_get_by_name(node, NULL);
+
+	if (!IS_ERR(external_clk)) {
+		arch_timer_rate = clk_get_rate(external_clk);
+		clk_prepare_enable(external_clk);
+	} else if (!of_property_read_u32(node, "clock-frequency", &freq)) {
 		arch_timer_rate = freq;
-	else
-		panic("clock-frequency not set in the .dts file");
+	} else {
+		panic("neither clock-frequency or clocks handle in .dts file");
+	}
 
 	/* Setup IRQ numbers */
 	timers.tmr_irq = irq_of_parse_and_map(node, 0);