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SubjectRe: [PATCH] rtc: jz4740: Add support for the JZ4725B, JZ4760, JZ4770
Hi,

Le ven. 20 juil. 2018 à 17:39, Rob Herring <robh@kernel.org> a écrit :
> On Sat, Jul 14, 2018 at 03:50:08PM +0200, Paul Cercueil wrote:
>>
>>
>> Le sam. 14 juil. 2018 à 15:32, Alexandre Belloni
>> <alexandre.belloni@bootlin.com> a écrit :
>> > On 14/07/2018 15:25:33+0200, Paul Cercueil wrote:
>> > > Hi Alexandre,
>> > >
>> > > Le sam. 14 juil. 2018 à 15:19, Alexandre Belloni
>> > > <alexandre.belloni@bootlin.com> a écrit :
>> > > > Hello,
>> > > >
>> > > > On 13/07/2018 17:14:24+0200, Paul Cercueil wrote:
>> > > > > The RTC in the JZ4725B works just like the one in the
>> JZ4740.
>> > > > >
>> > > > > The RTC in the JZ4760 and JZ4770 work just like the one
>> in the
>> > > > > JZ4780.
>> > > > >
>> > > > > Signed-off-by: Paul Cercueil <paul@crapouillou.net>
>> > > > > ---
>> > > > >
>> Documentation/devicetree/bindings/rtc/ingenic,jz4740-rtc.txt
>> > > | 3
>> > > > > +++
>> > > > > drivers/rtc/rtc-jz4740.c
>> > > | 11
>> > > > > ++++++++++-
>> > > > > 2 files changed, 13 insertions(+), 1 deletion(-)
>> > > > >
>> > > > > diff --git
>> > > > >
>> a/Documentation/devicetree/bindings/rtc/ingenic,jz4740-rtc.txt
>> > > > >
>> b/Documentation/devicetree/bindings/rtc/ingenic,jz4740-rtc.txt
>> > > > > index 41c7ae18fd7b..a9e821de84f2 100644
>> > > > > ---
>> > > a/Documentation/devicetree/bindings/rtc/ingenic,jz4740-rtc.txt
>> > > > > +++
>> > > b/Documentation/devicetree/bindings/rtc/ingenic,jz4740-rtc.txt
>> > > > > @@ -4,6 +4,9 @@ Required properties:
>> > > > >
>> > > > > - compatible: One of:
>> > > > > - "ingenic,jz4740-rtc" - for use with the JZ4740 SoC
>> > > > > + - "ingenic,jz4725b-rtc" - for use with the JZ4725B SoC
>> > > > > + - "ingenic,jz4760-rtc" - for use with the JZ4760 SoC
>> > > > > + - "ingenic,jz4770-rtc" - for use with the JZ4770 SoC
>> > > > > - "ingenic,jz4780-rtc" - for use with the JZ4780 SoC
>> > > > > - reg: Address range of rtc register set
>> > > > > - interrupts: IRQ number for the alarm interrupt
>> > > > > diff --git a/drivers/rtc/rtc-jz4740.c
>> > > b/drivers/rtc/rtc-jz4740.c
>> > > > > index d0a891777f44..1c867e3a0ea5 100644
>> > > > > --- a/drivers/rtc/rtc-jz4740.c
>> > > > > +++ b/drivers/rtc/rtc-jz4740.c
>> > > > > @@ -54,6 +54,9 @@
>> > > > >
>> > > > > enum jz4740_rtc_type {
>> > > > > ID_JZ4740,
>> > > > > + ID_JZ4725B,
>> > > > > + ID_JZ4760,
>> > > > > + ID_JZ4770,
>> > > >
>> > > > I wouldn't introduce those ids unless there are handling
>> > > differences at
>> > > > some point.
>> > >
>> > > Well there are handling differences, see below.
>> > >
>> > > > > ID_JZ4780,
>> > > > > };
>> > > > >
>> > > > > @@ -114,7 +117,7 @@ static inline int
>> > > jz4740_rtc_reg_write(struct
>> > > > > jz4740_rtc *rtc, size_t reg,
>> > > > > {
>> > > > > int ret = 0;
>> > > > >
>> > > > > - if (rtc->type >= ID_JZ4780)
>> > > > > + if (rtc->type >= ID_JZ4760)
>> > > >
>> > > > This would avoid that change (and the test would preferably
>> be
>> > > > (rtc->type == ID_JZ4780))
>> > >
>> > > That branch should be taken if the SoC is JZ4760, JZ4770 or
>> JZ4780.
>> > > It should not be taken if the SoC is JZ4740 or JZ4725B.
>> >
>> > Sure but you can achieve that with only 2 ids...
>> >
>> > >
>> > > > > ret = jz4780_rtc_enable_write(rtc);
>> > > > > if (ret == 0)
>> > > > > ret = jz4740_rtc_wait_write_ready(rtc);
>> > > > > @@ -300,6 +303,9 @@ static void jz4740_rtc_power_off(void)
>> > > > >
>> > > > > static const struct of_device_id jz4740_rtc_of_match[] =
>> {
>> > > > > { .compatible = "ingenic,jz4740-rtc", .data = (void
>> > > *)ID_JZ4740 },
>> > > > > + { .compatible = "ingenic,jz4725b-rtc", .data = (void
>> > > *)ID_JZ4725B
>> > > > > },
>> > > > > + { .compatible = "ingenic,jz4760-rtc", .data = (void
>> > > *)ID_JZ4760 },
>> > > > > + { .compatible = "ingenic,jz4770-rtc", .data = (void
>> > > *)ID_JZ4770 },
>> >
>> > By doing the correct mapping here e.g:
>> >
>> > { .compatible = "ingenic,jz4725b-rtc", .data = (void *)ID_JZ4740
>> },
>>
>> Not very pretty and future-proof if you ask me...
>
> Looks to me like this can be handled entirely in DT without driver
> changes like the other patches. Correct usage of compatible strings is
> what gives you future-proofing. And no driver change is better than
> needless changing.

If I make e.g. the jz4760 and jz4770 use the jz4780 compatible string,
but
then I want to implement a new feature that only exists on the jz4780,
how
can I do it without breaking everything?

> It may look a bit wierd if 4780 is the fallback for 4770, but if the
> 4780 is older, then that actually makes sense.

The 4770 is older than the 4780.

Thanks,
-Paul

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