linux-kernel - Re: [PATCH v3 5/6] Documentation: dt-bindings: Add binding info for X-Gene QMTM UIO driver

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Message-ID: <CAPTm99X9k+cfELMLL8_PmYN6RNn7CL7KugnV5JKcW6Jqhs8idg@mail.gmail.com>
Date:	Fri, 31 Oct 2014 15:34:06 +0530
From:	Ankit Jindal <ankit.jindal@...aro.org>
To:	Mark Rutland <mark.rutland@....com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Hans J. Koch" <hjk@...sjkoch.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"patches@....com" <patches@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Rob Herring <robh+dt@...nel.org>,
	Tushar Jagad <tushar.jagad@...aro.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Guenter Roeck <linux@...ck-us.net>,
	Varka Bhadram <varkabhadram@...il.com>
Subject: Re: [PATCH v3 5/6] Documentation: dt-bindings: Add binding info for
 X-Gene QMTM UIO driver

Hi Mark,

On 21 October 2014 14:44, Mark Rutland <mark.rutland@....com> wrote:
> On Tue, Oct 21, 2014 at 06:56:49AM +0100, Ankit Jindal wrote:
>> This patch adds device tree binding documentation for
>> X-Gene QMTM UIO driver.
>>
>> Signed-off-by: Ankit Jindal <ankit.jindal@...aro.org>
>> Signed-off-by: Tushar Jagad <tushar.jagad@...aro.org>
>> ---
>>  .../devicetree/bindings/uio/uio_xgene_qmtm.txt     |   53 ++++++++++++++++++++
>>  1 file changed, 53 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/uio/uio_xgene_qmtm.txt
>>
>> diff --git a/Documentation/devicetree/bindings/uio/uio_xgene_qmtm.txt b/Documentation/devicetree/bindings/uio/uio_xgene_qmtm.txt
>> new file mode 100644
>> index 0000000..288ed92
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/uio/uio_xgene_qmtm.txt
>> @@ -0,0 +1,53 @@
>> +APM X-Gene QMTM UIO nodes
>
> The "UIO" can go.
Sure.

>
>> +The Applied Micro X-Gene SOC has on-chip QMTM (Queue manager
>> +and Traffic manager). It is a device for managing hardware queues.
>> +It also implements QoS among hardware queues hence term "traffic"
>> +manager is present in its name. QMTM UIO nodes are defined for user
>> +space access to this device using UIO framework.
>
> The binding should describe the hardware, not the software. Please drop
> mention of UIO, userspace, etc.
Sure.

>
>> +Required properties:
>> +- compatible: Should be "apm,xgene-qmtm"
>> +- reg: Address and length of the register set for the device. It contains the
>> +  information of registers in the same order as described by reg-names.
>> +- reg-names: Should contain the register set names
>> +  - "csr": QMTM control and status register address space.
>> +  - "fabric": QMTM memory mapped access to queue states.
>> +- qpool: Points to the phandle of the node defining memory location for
>> +      creating QMTM queues. This could point either to the reserved-memory
>> +      node (as-per reserved memory bindings) or to the node of on-chip
>> +      SRAM etc. It is expected that size and location of qpool memory will
>> +      be configurable via bootloader.
>
> Is that on-chip SRAM part of the QMTM, or is that a shared part of the
> SoC?
Its not part of QMTM.

>
> It feels odd to have a phandle that can go to completely different
> classes of node, especially as you will need to use a different API to
> acquire the memory region within Linux.
It is expected that phandle will point to a node whose first reg
property will be only for qpool memory.

>
>> +- clocks: Reference to the clock entry.
>
> Just the one clock? Does the clock input to the QMTM have a name?
Just one input clock. There is no specific name of it.

>
>> +- num-queues: Number of queues under this QMTM device.
>> +- devid: QMTM identification number for the system having multiple QMTM devices.
>> +      This is used to form a unique id (a tuple of queue number and
>> +      device id) for the queues belonging to this device.
>
> Is this just an arbitrary unique ID, or is this a non-probeable property
> of the HW? If the former, isn't the base address sufficient as a unique
> identifier?
Its a non-probeable property of the HW.

Thanks,
Ankit
>
> Thanks,
> Mark.
>
>> +Example:
>> +     qmtm1_uio_qpool: qmtm1_uio_qpool {
>> +             reg = <0x0 0x0 0x0 0x0>
>> +     };
>> +
>> +     qmtm1clk: qmtmclk@...0c000 {
>> +             compatible = "apm,xgene-device-clock";
>> +             clock-output-names = "qmtm1clk";
>> +             status = "ok";
>> +     };
>> +
>> +     qmtm1_uio: qmtm_uio@...00000 {
>> +             compatible = "apm,xgene-qmtm";
>> +             status = "disabled";
>> +             reg = <0x0 0x1f200000 0x0 0x10000>,
>> +                   <0x0 0x1b000000 0x0 0x400000>;
>> +             reg-names = "csr", "fabric";
>> +             qpool = <&qmtm1_uio_qpool>;
>> +             clocks = <&qmtm1clk 0>;
>> +             num-queues = <0x400>;
>> +             devid = <1>;
>> +     };
>> +
>> +     /* Board-specific peripheral configurations */
>> +     &qmtm1_uio {
>> +             status = "ok";
>> +     };
>> --
>> 1.7.9.5
>>
>> --
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