On 25/05/17 14:22, Jassi Brar wrote:
> On Wed, May 24, 2017 at 3:46 PM, Sudeep Holla <sudeep.ho...@arm.com> wrote:
>> The ARM MHU has mechanism to assert interrupt signals to facilitate
>> inter-processor message based communication. It drives the signal using
>> a 32-bit register, with all 32-bits logically ORed together. It also
>> enables software to set, clear and check the status of each of the bits
>> of this register independently. Each bit of the register can be
>> associated with a type of event that can contribute to raising the
>> interrupt thereby allowing it to be used as independent doorbells.
>>
>> Since the first version of this binding can't support doorbells,
>> this patch extends the existing binding to support them.
>>
>> Cc: Alexey Klimov <alexey.kli...@arm.com>
>> Cc: Jassi Brar <jaswinder.si...@linaro.org>
>> Cc: Rob Herring <robh...@kernel.org>
>> Cc: devicet...@vger.kernel.org
>> Signed-off-by: Sudeep Holla <sudeep.ho...@arm.com>
>> ---
>> .../devicetree/bindings/mailbox/arm-mhu.txt | 46
>> ++++++++++++++++++++--
>> 1 file changed, 43 insertions(+), 3 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/mailbox/arm-mhu.txt
>> b/Documentation/devicetree/bindings/mailbox/arm-mhu.txt
>> index 4971f03f0b33..bd9a3a267caf 100644
>> --- a/Documentation/devicetree/bindings/mailbox/arm-mhu.txt
>> +++ b/Documentation/devicetree/bindings/mailbox/arm-mhu.txt
>> @@ -10,21 +10,42 @@ STAT register and the remote clears it after having read
>> the data.
>> The last channel is specified to be a 'Secure' resource, hence can't be
>> used by Linux running NS.
>>
>> +The MHU drives the interrupt signal using a 32-bit register, with all
>> +32-bits logically ORed together. It provides a set of registers to
>> +enable software to set, clear and check the status of each of the bits
>> +of this register independently. The use of 32 bits per interrupt line
>> +enables software to provide more information about the source of the
>> +interrupt. For example, each bit of the register can be associated with
>> +a type of event that can contribute to raising the interrupt. Each of
>> +the 32-bits can be used as "doorbell" to alert the remote processor.
>> +
>> Mailbox Device Node:
>> ====================
>>
>> Required properties:
>> --------------------
>> -- compatible: Shall be "arm,mhu" & "arm,primecell"
>> +- compatible: Shall be "arm,primecell" and one of the below:
>> + "arm,mhu" - if the controller doesn't support
>> + doorbell model
>> + "arm,mhu-doorbell" - if the controller supports
>> + doorbell model
>> - reg: Contains the mailbox register address range (base
>> address and length)
>> -- #mbox-cells Shall be 1 - the index of the channel needed.
>> +- #mbox-cells Shall be 1 - the index of the channel needed when
>> + compatible is "arm,mhu"
>> + Shall be 2 - the index of the channel needed, and
>> + the index of the doorbell bit with the channel when
>> + compatible is "arm,mhu-doorbell"
>> - interrupts: Contains the interrupt information corresponding to
>> - each of the 3 links of MHU.
>> + each of the 3 physical channels of MHU namely low
>> + priority non-secure, high priority non-secure and
>> + secure channels.
>>
>> Example:
>> --------
>>
>> +1. Controller which doesn't support doorbells
>> +
>> mhu: mailbox@2b1f0000 {
>> #mbox-cells = <1>;
>> compatible = "arm,mhu", "arm,primecell";
>> @@ -41,3 +62,22 @@ used by Linux running NS.
>> reg = <0 0x2e000000 0x4000>;
>> mboxes = <&mhu 1>; /* HP-NonSecure */
>> };
>> +
>> +2. Controller which supports doorbells
>> +
>> + mhu: mailbox@2b1f0000 {
>> + #mbox-cells = <2>;
>> + compatible = "arm,mhu-doorbell", "arm,primecell";
>> + reg = <0 0x2b1f0000 0x1000>;
>> + interrupts = <0 36 4>, /* LP-NonSecure */
>> + <0 35 4>, /* HP-NonSecure */
>> + <0 37 4>; /* Secure */
>> + clocks = <&clock 0 2 1>;
>> + clock-names = "apb_pclk";
>> + };
>> +
>> + mhu_client: scb@2e000000 {
>> + compatible = "arm,scpi";
>> + reg = <0 0x2e000000 0x200>;
>> + mboxes = <&mhu 1 4>; /* HP-NonSecure 5th doorbell bit */
>> + };
>>
> Every MHU controller can by driven as "arm,mhu-doorbell" or "arm,mhu"
> equally fine. So you are basically smuggling a s/w feature into DT.
>
I disagree, the spec clearly says each bit can be used for different
event and hence we need a way to specify that in DT when used as doorbell.
--
Regards,
Sudeep
