From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jean-Christophe PLAGNIOL-VILLARD Subject: Re: [RFC 4/5] RTC: rtc-at91sam9: add device-tree support Date: Mon, 8 Apr 2013 13:11:13 +0200 Message-ID: <20130408111113.GX20693@game.jcrosoft.org> References: <20130407150938.GA25605@localhost> <1365347572-14972-1-git-send-email-jhovold@gmail.com> <1365347572-14972-4-git-send-email-jhovold@gmail.com> <20130408073807.GQ20693@game.jcrosoft.org> <20130408090023.GC25605@localhost> <51629472.3070404@atmel.com> <20130408103847.GE25605@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20130408103847.GE25605@localhost> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Sender: "devicetree-discuss" To: Johan Hovold Cc: devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, Robert Nelson , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, dgilbert-qazKcTl6WRFWk0Htik3J/w@public.gmane.org List-Id: devicetree@vger.kernel.org On 12:38 Mon 08 Apr , Johan Hovold wrote: > On Mon, Apr 08, 2013 at 11:57:06AM +0200, Nicolas Ferre wrote: > > On 04/08/2013 11:00 AM, Johan Hovold : > > > On Mon, Apr 08, 2013 at 09:38:07AM +0200, Jean-Christophe PLAGNIOL-VILLARD wrote: > > >> On 17:12 Sun 07 Apr , Johan Hovold wrote: > > >>> Add device-tree support. > > >>> > > >>> The AT91 RTT can be used as an RTC if the atmel,at91-rtt-as-rtc-gpbr > > >>> property is present and set to the general-purpose backup register to > > >>> use to store the RTC time base. > > >>> > > >>> Signed-off-by: Johan Hovold > > >>> --- > > >>> .../devicetree/bindings/rtc/rtc-at91sam9.txt | 19 ++++++++++++ > > >>> drivers/rtc/rtc-at91sam9.c | 36 +++++++++++++++++++++- > > >>> 2 files changed, 54 insertions(+), 1 deletion(-) > > >>> create mode 100644 Documentation/devicetree/bindings/rtc/rtc-at91sam9.txt > >>> > > >>> diff --git > > >>> a/Documentation/devicetree/bindings/rtc/rtc-at91sam9.txt > > >>> b/Documentation/devicetree/bindings/rtc/rtc-at91sam9.txt > >>> new > > >>> file mode 100644 > > >>> index 0000000..0f54988 > > >>> --- /dev/null > > >>> +++ b/Documentation/devicetree/bindings/rtc/rtc-at91sam9.txt > > >>> @@ -0,0 +1,19 @@ > > >>> +Atmel AT91 RTT as RTC > > >>> +===================== > > >>> + > > >>> +Required properties: > > >>> +- compatible: Should be "atmel,at91sam9260-rtt" > > >>> +- reg: Should contain register location and length > > >>> +- interrupts: Should contain interrupt for the RTT which is the IRQ line > > >>> + shared across all System Controller members. > > >>> +- atmel,rtt-as-rtc-gpbr: Should contain the backup-register to use to store > > >>> + the RTC time base > > >>> + > > >>> +Example: > > >>> + > > >>> +rtt@fffffd20 { > > >>> + compatible = "atmel,at91sam9g45-rtt", "atmel,at91sam9260-rtt"; > > > > No, there is no visible difference between the sam9g45 RTT and the > > sam9260 one. So the most precise compatibility string is still sam9260. > > If one day we feel the need for a advanced feature that exists on a more > > recent SoC, we have the possibility to add it at that time... > > Yes, this should be just "atmel,at91sam9260-rtt" to follow the current > practise in AT91. However, as I mentioned in an earlier mail one could > interpret > > "The first string in the list specifies the exact device that > the node represents in the form ",". The > following strings represent other devices that the device is > compatible with. > > For example, the Freescale MPC8349 System on Chip (SoC) has a > serial device which implements the National Semiconductor > ns16550 register interface. The compatible property for the > MPC8349 serial device should therefore be: compatible = > "fsl,mpc8349-uart", "ns16550". In this case, fsl,mpc8349-uart > specifies the exact device, and ns16550 states that it is > register-level compatible with a National Semiconductor 16550 > UART." > > http://www.devicetree.org/Device_Tree_Usage#Understanding_the_compatible_Property > > to mean that the compatible property should always be exact SoC-IP > followed by the first (most generic) compatible one. here you describe compatible IP not drivers implementation they are both usuart IP that are compatible at IP level. Best Regards, J.