Re: [PATCH v2 2/2] rtc: omap: Add external clock enabling support

[Keerthy <a0393675-l0cyMroinI0@public.gmane.org>]

On Monday 17 August 2015 05:00 PM, Johan Hovold wrote:
> On Mon, Aug 17, 2015 at 10:25:38AM +0530, Keerthy wrote:
>> Configure the clock source to either internal clock
>> or external clock based on the availability of the clocks.
>> External clock is preferred as it can be ticking during suspend.
>>
>> Signed-off-by: Keerthy <j-keerthy-l0cyMroinI0@public.gmane.org>
>> ---
>>
>> Changes in V2:
>>
>>    * Changed clk_prepare calls to clk_prepare_enable.
>>    * Changed clk_unprepare calls to clk_disable_unprepare.
>>    * Added clk pointers for external and internal clock to omap_rtc structure.
>>
>>   drivers/rtc/rtc-omap.c | 40 ++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 40 insertions(+)
>>
>> diff --git a/drivers/rtc/rtc-omap.c b/drivers/rtc/rtc-omap.c
>> index 8b6355f..46b3944 100644
>> --- a/drivers/rtc/rtc-omap.c
>> +++ b/drivers/rtc/rtc-omap.c
>> @@ -25,6 +25,7 @@
>>   #include <linux/of_device.h>
>>   #include <linux/pm_runtime.h>
>>   #include <linux/io.h>
>> +#include <linux/clk.h>
>>
>>   /*
>>    * The OMAP RTC is a year/month/day/hours/minutes/seconds BCD clock
>> @@ -107,6 +108,7 @@
>>
>>   /* OMAP_RTC_OSC_REG bit fields: */
>>   #define OMAP_RTC_OSC_32KCLK_EN		BIT(6)
>> +#define OMAP_RTC_OSC_SEL_32KCLK_SRC	BIT(3)
>>
>>   /* OMAP_RTC_IRQWAKEEN bit fields: */
>>   #define OMAP_RTC_IRQWAKEEN_ALARM_WAKEEN	BIT(1)
>> @@ -132,10 +134,13 @@ struct omap_rtc_device_type {
>>   struct omap_rtc {
>>   	struct rtc_device *rtc;
>>   	void __iomem *base;
>> +	struct clk *ext_clk;
>> +	struct clk *int_clk;
>
> As was already suggested, you could just use one clock here for now.

If the intent is to enable dynamic switching in future why not have both 
the clock pointers ready?

>
>>   	int irq_alarm;
>>   	int irq_timer;
>>   	u8 interrupts_reg;
>>   	bool is_pmic_controller;
>> +	bool has_ext_clk;
>>   	const struct omap_rtc_device_type *type;
>>   };
>>
>> @@ -553,6 +558,17 @@ static int omap_rtc_probe(struct platform_device *pdev)
>>   	if (rtc->irq_alarm <= 0)
>>   		return -ENOENT;
>>
>> +	rtc->ext_clk = devm_clk_get(&pdev->dev, "ext-clk");
>> +	if (!IS_ERR(rtc->ext_clk)) {
>> +		rtc->has_ext_clk = true;
>> +		clk_prepare_enable(rtc->ext_clk);
>> +	} else {
>> +		rtc->int_clk = devm_clk_get(&pdev->dev, "int-clk");
>> +
>> +		if (!IS_ERR(rtc->int_clk))
>> +			clk_prepare_enable(rtc->int_clk);
>> +	}
>> +
>
> Which would allow some simplification here.
>
> But shouldn't enabling the internal clock go in its own patch before you
> add support for the external clock?

I am okay with splitting but for now its either or situation so enabling 
in one patch made sense to me.

>
>>   	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>   	rtc->base = devm_ioremap_resource(&pdev->dev, res);
>>   	if (IS_ERR(rtc->base))
>> @@ -627,6 +643,16 @@ static int omap_rtc_probe(struct platform_device *pdev)
>>   	if (reg != new_ctrl)
>>   		rtc_write(rtc, OMAP_RTC_CTRL_REG, new_ctrl);
>>
>> +	/*
>> +	 * If we have the external clock then switch to it so we can keep
>> +	 * ticking acorss suspend.
>
> You forgot to fix the "acorss" typo.

I will fix it.

>
>> +	 */
>> +	if (rtc->has_ext_clk) {
>> +		reg = rtc_read(rtc, OMAP_RTC_OSC_REG);
>> +		rtc_write(rtc, OMAP_RTC_OSC_REG, reg |
>> +			  OMAP_RTC_OSC_SEL_32KCLK_SRC);
>
> Odd line break, break after the final comma instead?

Okay. I will fix it.

>
>> +	}
>> +
>>   	rtc->type->lock(rtc);
>>
>>   	device_init_wakeup(&pdev->dev, true);
>> @@ -672,6 +698,7 @@ err:
>>   static int __exit omap_rtc_remove(struct platform_device *pdev)
>>   {
>>   	struct omap_rtc *rtc = platform_get_drvdata(pdev);
>> +	u8 reg;
>>
>>   	if (pm_power_off == omap_rtc_power_off &&
>>   			omap_rtc_power_off_rtc == rtc) {
>> @@ -681,10 +708,23 @@ static int __exit omap_rtc_remove(struct platform_device *pdev)
>>
>>   	device_init_wakeup(&pdev->dev, 0);
>>
>> +	if (!IS_ERR(rtc->ext_clk)) {
>> +		clk_disable_unprepare(rtc->ext_clk);
>> +	} else {
>> +		if (!IS_ERR(rtc->int_clk))
>> +			clk_disable_unprepare(rtc->int_clk);
>> +	}
>> +
>
> This could also be simplified with a single clock entry in rtc.
>
>>   	rtc->type->unlock(rtc);
>>   	/* leave rtc running, but disable irqs */
>>   	rtc_write(rtc, OMAP_RTC_INTERRUPTS_REG, 0);
>>
>> +	if (rtc->has_ext_clk) {
>> +		reg = rtc_read(rtc, OMAP_RTC_OSC_REG);
>> +		reg &= ~OMAP_RTC_OSC_SEL_32KCLK_SRC;
>> +		rtc_write(rtc, OMAP_RTC_OSC_REG, reg);
>> +	}
>> +
>>   	rtc->type->lock(rtc);
>>
>>   	/* Disable the clock/module */
>
> Johan
>
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