[v7,1/6] dt-bindings: mailbox: allow mbox-cells to be equal to 0
diff mbox series

Message ID 20180726065331.6186-2-o.rempel@pengutronix.de
State Not Applicable
Headers show
Series
  • add mailbox support for i.MX7D
Related show

Commit Message

Oleksij Rempel July 26, 2018, 6:53 a.m. UTC
From: Dong Aisheng <aisheng.dong@nxp.com>

Mailbox devices may have only one channel which means the mbox-cells
at least 1 does not make sense for this type devices. Let's remove
that limitation to allow the mbox-cells to be equal to 0.

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
---
 Documentation/devicetree/bindings/mailbox/mailbox.txt | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

Comments

Jassi Brar July 26, 2018, 9:41 a.m. UTC | #1
On Thu, Jul 26, 2018 at 12:23 PM, Oleksij Rempel
<o.rempel@pengutronix.de> wrote:
> From: Dong Aisheng <aisheng.dong@nxp.com>
>
> Mailbox devices may have only one channel which means the mbox-cells
> at least 1 does not make sense for this type devices. Let's remove
> that limitation to allow the mbox-cells to be equal to 0.
>
OK

But please realise that you'll have to write more code -- implement
your own of_xlate() callback.
Most developers would prefer to call the only channel as channel
number 0, and use the common of_xlate implementation.

-jassi
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Aisheng Dong July 26, 2018, 11 a.m. UTC | #2
> -----Original Message-----
> From: Jassi Brar [mailto:jassisinghbrar@gmail.com]
> Sent: Thursday, July 26, 2018 5:42 PM
> To: Oleksij Rempel <o.rempel@pengutronix.de>
> Cc: Shawn Guo <shawnguo@kernel.org>; Fabio Estevam
> <fabio.estevam@nxp.com>; Rob Herring <robh+dt@kernel.org>; Mark
> Rutland <mark.rutland@arm.com>; A.s. Dong <aisheng.dong@nxp.com>;
> Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>; Sudeep Holla
> <sudeep.holla@arm.com>; Devicetree List <devicetree@vger.kernel.org>;
> Linux Kernel Mailing List <linux-kernel@vger.kernel.org>; , Sascha Hauer
> <kernel@pengutronix.de>; , linux-arm-kernel@lists.infradead.org, linux-
> mediatek@lists.infradead.org, srv_heupstream <linux-arm-
> kernel@lists.infradead.org>; dl-linux-imx <linux-imx@nxp.com>
> Subject: Re: [PATCH v7 1/6] dt-bindings: mailbox: allow mbox-cells to be
> equal to 0
> 
> On Thu, Jul 26, 2018 at 12:23 PM, Oleksij Rempel <o.rempel@pengutronix.de>
> wrote:
> > From: Dong Aisheng <aisheng.dong@nxp.com>
> >
> > Mailbox devices may have only one channel which means the mbox-cells
> > at least 1 does not make sense for this type devices. Let's remove
> > that limitation to allow the mbox-cells to be equal to 0.
> >
> OK
> 
> But please realise that you'll have to write more code -- implement your own
> of_xlate() callback.
> Most developers would prefer to call the only channel as channel number 0,
> and use the common of_xlate implementation.
> 

Yes, that's true because the common of_xlate assuming the mbox-cells is 1.
And there's already such users:
arch/arm/boot/dts/bcm283x.dtsi

More comments will be on your reply of patch-3.

Regards
Dong Aisheng

> -jassi
Jassi Brar July 26, 2018, 11:36 a.m. UTC | #3
On Thu, Jul 26, 2018 at 4:30 PM, A.s. Dong <aisheng.dong@nxp.com> wrote:
>> -----Original Message-----
>> From: Jassi Brar [mailto:jassisinghbrar@gmail.com]
>> Sent: Thursday, July 26, 2018 5:42 PM
>> To: Oleksij Rempel <o.rempel@pengutronix.de>
>> Cc: Shawn Guo <shawnguo@kernel.org>; Fabio Estevam
>> <fabio.estevam@nxp.com>; Rob Herring <robh+dt@kernel.org>; Mark
>> Rutland <mark.rutland@arm.com>; A.s. Dong <aisheng.dong@nxp.com>;
>> Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>; Sudeep Holla
>> <sudeep.holla@arm.com>; Devicetree List <devicetree@vger.kernel.org>;
>> Linux Kernel Mailing List <linux-kernel@vger.kernel.org>; , Sascha Hauer
>> <kernel@pengutronix.de>; , linux-arm-kernel@lists.infradead.org, linux-
>> mediatek@lists.infradead.org, srv_heupstream <linux-arm-
>> kernel@lists.infradead.org>; dl-linux-imx <linux-imx@nxp.com>
>> Subject: Re: [PATCH v7 1/6] dt-bindings: mailbox: allow mbox-cells to be
>> equal to 0
>>
>> On Thu, Jul 26, 2018 at 12:23 PM, Oleksij Rempel <o.rempel@pengutronix.de>
>> wrote:
>> > From: Dong Aisheng <aisheng.dong@nxp.com>
>> >
>> > Mailbox devices may have only one channel which means the mbox-cells
>> > at least 1 does not make sense for this type devices. Let's remove
>> > that limitation to allow the mbox-cells to be equal to 0.
>> >
>> OK
>>
>> But please realise that you'll have to write more code -- implement your own
>> of_xlate() callback.
>> Most developers would prefer to call the only channel as channel number 0,
>> and use the common of_xlate implementation.
>>
>
> Yes, that's true because the common of_xlate assuming the mbox-cells is 1.
> And there's already such users:
> arch/arm/boot/dts/bcm283x.dtsi
>
You mean that is a good thing, right?
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Jassi Brar July 26, 2018, 12:04 p.m. UTC | #4
On Thu, Jul 26, 2018 at 5:25 PM, A.s. Dong <aisheng.dong@nxp.com> wrote:
>> -----Original Message-----
>> From: Jassi Brar [mailto:jassisinghbrar@gmail.com]
>> Sent: Thursday, July 26, 2018 7:37 PM
>> To: A.s. Dong <aisheng.dong@nxp.com>
>> Cc: Oleksij Rempel <o.rempel@pengutronix.de>; Shawn Guo
>> <shawnguo@kernel.org>; Fabio Estevam <fabio.estevam@nxp.com>; Rob
>> Herring <robh+dt@kernel.org>; Mark Rutland <mark.rutland@arm.com>;
>> Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>; Sudeep Holla
>> <sudeep.holla@arm.com>; Devicetree List <devicetree@vger.kernel.org>;
>> Linux Kernel Mailing List <linux-kernel@vger.kernel.org>; , Sascha Hauer
>> <kernel@pengutronix.de>; , linux-arm-kernel@lists.infradead.org, linux-
>> mediatek@lists.infradead.org, srv_heupstream <linux-arm-
>> kernel@lists.infradead.org>; dl-linux-imx <linux-imx@nxp.com>
>> Subject: Re: [PATCH v7 1/6] dt-bindings: mailbox: allow mbox-cells to be
>> equal to 0
>>
>> On Thu, Jul 26, 2018 at 4:30 PM, A.s. Dong <aisheng.dong@nxp.com> wrote:
>> >> -----Original Message-----
>> >> From: Jassi Brar [mailto:jassisinghbrar@gmail.com]
>> >> Sent: Thursday, July 26, 2018 5:42 PM
>> >> To: Oleksij Rempel <o.rempel@pengutronix.de>
>> >> Cc: Shawn Guo <shawnguo@kernel.org>; Fabio Estevam
>> >> <fabio.estevam@nxp.com>; Rob Herring <robh+dt@kernel.org>; Mark
>> >> Rutland <mark.rutland@arm.com>; A.s. Dong <aisheng.dong@nxp.com>;
>> >> Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>; Sudeep Holla
>> >> <sudeep.holla@arm.com>; Devicetree List <devicetree@vger.kernel.org>;
>> >> Linux Kernel Mailing List <linux-kernel@vger.kernel.org>; , Sascha
>> >> Hauer <kernel@pengutronix.de>; ,
>> >> linux-arm-kernel@lists.infradead.org, linux-
>> >> mediatek@lists.infradead.org, srv_heupstream <linux-arm-
>> >> kernel@lists.infradead.org>; dl-linux-imx <linux-imx@nxp.com>
>> >> Subject: Re: [PATCH v7 1/6] dt-bindings: mailbox: allow mbox-cells to
>> >> be equal to 0
>> >>
>> >> On Thu, Jul 26, 2018 at 12:23 PM, Oleksij Rempel
>> >> <o.rempel@pengutronix.de>
>> >> wrote:
>> >> > From: Dong Aisheng <aisheng.dong@nxp.com>
>> >> >
>> >> > Mailbox devices may have only one channel which means the
>> >> > mbox-cells at least 1 does not make sense for this type devices.
>> >> > Let's remove that limitation to allow the mbox-cells to be equal to 0.
>> >> >
>> >> OK
>> >>
>> >> But please realise that you'll have to write more code -- implement
>> >> your own
>> >> of_xlate() callback.
>> >> Most developers would prefer to call the only channel as channel
>> >> number 0, and use the common of_xlate implementation.
>> >>
>> >
>> > Yes, that's true because the common of_xlate assuming the mbox-cells is 1.
>> > And there's already such users:
>> > arch/arm/boot/dts/bcm283x.dtsi
>> >
>> You mean that is a good thing, right?
>
> No, I mean there's similar HW in kernel already that only has one channel.
> Are you suggesting even for one channel mailbox, we should still use
> Mbox-cells 1 and use 'mboxes = <&mailbox 0>' in devicetree?
>
As i said, I am ok with the mbox-cells to be 0.

But if you have two instances of the controller, one with 4 channels
and the other with 1 channel. Then you can/should not have different
bindings.

And, if the controller can have only 1 channel, then please feel free
to have mbox-cells=0 and implement your own of_xlate().
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Patch
diff mbox series

diff --git a/Documentation/devicetree/bindings/mailbox/mailbox.txt b/Documentation/devicetree/bindings/mailbox/mailbox.txt
index af8ecee2ac68..c2fcd054141a 100644
--- a/Documentation/devicetree/bindings/mailbox/mailbox.txt
+++ b/Documentation/devicetree/bindings/mailbox/mailbox.txt
@@ -6,8 +6,7 @@  assign appropriate mailbox channel to client drivers.
 * Mailbox Controller
 
 Required property:
-- #mbox-cells: Must be at least 1. Number of cells in a mailbox
-		specifier.
+- #mbox-cells: Number of cells in a mailbox specifier.
 
 Example:
 	mailbox: mailbox {