Re: [PATCH 4/5] rtc: at91sam9: retain slow clock and check its rate

Nicolas Ferre
2014-09-09T08:36:45Z

On 08/09/2014 21:37, Boris BREZILLON :
> On Mon, 8 Sep 2014 21:22:18 +0200
> Boris BREZILLON <boris.brezillon@free-electrons.com> wrote:
>
>> On Mon, 8 Sep 2014 19:33:38 +0200
>> Alexandre Belloni <alexandre.belloni@free-electrons.com> wrote:
>>
>>> On 03/09/2014 at 10:45:33 +0200, Boris Brezillon wrote :
>>>> The RTT block is using the slow clock and expect it to run at 32KHz.
>>>> Now that we moved to the CCF it's better to retain the clk reference so
>>>> that the CCF can't disable the slow clock considering it is unused.
>>>>
>>>> Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
>>>> ---
>>>> drivers/rtc/rtc-at91sam9.c | 24 ++++++++++++++++++++++++
>>>> 1 file changed, 24 insertions(+)
>>>>
>>>> diff --git a/drivers/rtc/rtc-at91sam9.c b/drivers/rtc/rtc-at91sam9.c
>>>> index 57014b7..5c5093b 100644
>>>> --- a/drivers/rtc/rtc-at91sam9.c
>>>> +++ b/drivers/rtc/rtc-at91sam9.c
>>>> @@ -21,6 +21,7 @@
>>>> #include <linux/slab.h>
>>>> #include <linux/platform_data/atmel.h>
>>>> #include <linux/io.h>
>>>> +#include <linux/clk.h>
>>>>
>>>> /*
>>>> * This driver uses two configurable hardware resources that live in the
>>>> @@ -74,6 +75,7 @@ struct sam9_rtc {
>>>> u32 imr;
>>>> void __iomem *gpbr;
>>>> int irq;
>>>> + struct clk *sclk;
>>>> };
>>>>
>>>> #define rtt_readl(rtc, field) \
>>>> @@ -373,6 +375,25 @@ static int at91_rtc_probe(struct platform_device *pdev)
>>>> return ret;
>>>> }
>>>>
>>>> + /* Retain slow clk if it is specified in the DT.
>>>> + * Do not complain if slow clk is missing, but check its rate
>>>> + * if it is available.
>>>> + */
>>>> + rtc->sclk = devm_clk_get(&pdev->dev, NULL);
>>>> + if (!IS_ERR(rtc->sclk)) {
>>>> + if (clk_get_rate(rtc->sclk) != AT91_SLOW_CLOCK) {
>>>
>>> I would not bother doing that check but use the value for MR instead of
>>> AT91_SLOW_CLOCK (see my previous mail).
>>
>> Unfortunately, we can't get rid of this macro without modifying the
>> clk_lookup table in several arch/arm/mach-at91/<soc-name>.c files in
>> order to handle non DT/CCF cases (which will remain until all non DT
>> boards are moved to DT).
>
> After taking a closer look at what should be modified, I think it's
> worth it: there's only 5 impacted files (at91sam9260.c, at91sam9261.c,
> at91sam9263.c, at91sam9rl.c and at91sam9g45.c) and adding a clk_lookup
> entry is pretty easy.
>
> Moreover we'll end up with a clean driver and won't have to bother
> about cleaning it up when dropping non DT boards support.

I vote for this => +1 ;-)

Bye,
--
Nicolas Ferre