[PATCH 1/3] Docs: dt: add generic MSI bindings
Rob Herring
robherring2 at gmail.com
Mon Aug 24 06:37:59 PDT 2015
On Mon, Aug 24, 2015 at 5:17 AM, Mark Rutland <mark.rutland at arm.com> wrote:
> On Wed, Aug 05, 2015 at 05:51:20PM +0100, Mark Rutland wrote:
>> Rob,
>>
>> Do you have any objections to this, or are you happy to take this patch?
>>
>> There's a user of this binding (the GICv3 ITS) queued for v4.3 already in
>> the tip tree, so either we either need to be ok with this binding or we
>> need to rework that before v4.3.
>
> Sorry to ping, but are you happy to take this? Marc's replied and
> provided his ack.
Sorry. Looks fine to me, so I'll apply.
> I'm happy to resend if you prefer?
What about patch 2 and 3? I can't find patch 3 in my mail.
Rob
>
> Thanks,
> Mark.
>
>> Marc, can I take it from your use of the binding that you are happy to
>> provide your ack?
>>
>> Thanks,
>> Mark.
>>
>> On Thu, Jul 23, 2015 at 05:52:43PM +0100, Mark Rutland wrote:
>> > Currently msi-parent is used in a couple of drivers despite being fairly
>> > underspecified. This patch adds a generic binding for MSIs (including
>> > the existing msi-parent property) enabling the description of platform
>> > devices capable of using MSIs.
>> >
>> > While MSIs are primarily distinguished by doorbell and payload, some MSI
>> > controllers (e.g. the GICv3 ITS) also use side-band information
>> > accompanying the write to identify the master which originated the MSI,
>> > to allow for sandboxing. This sideband information is non-probeable and
>> > needs to be described in the DT. Other MSI controllers may have
>> > additional configuration details which need to be described per-master.
>> >
>> > This patch adds a generic msi-parent binding document, extending the
>> > de-facto standard with a new (optional) #msi-cells which can be used to
>> > express any per-master configuration and/or sideband data. This is
>> > sufficient to describe non-hotpluggable devices.
>> >
>> > For busses where sideband data may be derived from some bus-specific
>> > master ID scheme, other properties will be required to describe the
>> > mapping.
>> >
>> > Signed-off-by: Mark Rutland <mark.rutland at arm.com>
>> > ---
>> > .../bindings/interrupt-controller/msi.txt | 135 +++++++++++++++++++++
>> > 1 file changed, 135 insertions(+)
>> > create mode 100644 Documentation/devicetree/bindings/interrupt-controller/msi.txt
>> >
>> > diff --git a/Documentation/devicetree/bindings/interrupt-controller/msi.txt b/Documentation/devicetree/bindings/interrupt-controller/msi.txt
>> > new file mode 100644
>> > index 0000000..c60c034
>> > --- /dev/null
>> > +++ b/Documentation/devicetree/bindings/interrupt-controller/msi.txt
>> > @@ -0,0 +1,135 @@
>> > +This document describes the generic device tree binding for MSI controllers and
>> > +their master(s).
>> > +
>> > +Message Signaled Interrupts (MSIs) are a class of interrupts generated by a
>> > +write to an MMIO address.
>> > +
>> > +MSIs were originally specified by PCI (and are used with PCIe), but may also be
>> > +used with other busses, and hence a mechanism is required to relate devices on
>> > +those busses to the MSI controllers which they are capable of using,
>> > +potentially including additional information.
>> > +
>> > +MSIs are distinguished by some combination of:
>> > +
>> > +- The doorbell (the MMIO address written to).
>> > +
>> > + Devices may be configured by software to write to arbitrary doorbells which
>> > + they can address. An MSI controller may feature a number of doorbells.
>> > +
>> > +- The payload (the value written to the doorbell).
>> > +
>> > + Devices may be configured to write an arbitrary payload chosen by software.
>> > + MSI controllers may have restrictions on permitted payloads.
>> > +
>> > +- Sideband information accompanying the write.
>> > +
>> > + Typically this is neither configurable nor probeable, and depends on the path
>> > + taken through the memory system (i.e. it is a property of the combination of
>> > + MSI controller and device rather than a property of either in isolation).
>> > +
>> > +
>> > +MSI controllers:
>> > +================
>> > +
>> > +An MSI controller signals interrupts to a CPU when a write is made to an MMIO
>> > +address by some master. An MSI controller may feature a number of doorbells.
>> > +
>> > +Required properties:
>> > +--------------------
>> > +
>> > +- msi-controller: Identifies the node as an MSI controller.
>> > +
>> > +Optional properties:
>> > +--------------------
>> > +
>> > +- #msi-cells: The number of cells in an msi-specifier, required if not zero.
>> > +
>> > + Typically this will encode information related to sideband data, and will
>> > + not encode doorbells or payloads as these can be configured dynamically.
>> > +
>> > + The meaning of the msi-specifier is defined by the device tree binding of
>> > + the specific MSI controller.
>> > +
>> > +
>> > +MSI clients
>> > +===========
>> > +
>> > +MSI clients are devices which generate MSIs. For each MSI they wish to
>> > +generate, the doorbell and payload may be configured, though sideband
>> > +information may not be configurable.
>> > +
>> > +Required properties:
>> > +--------------------
>> > +
>> > +- msi-parent: A list of phandle + msi-specifier pairs, one for each MSI
>> > + controller which the device is capable of using.
>> > +
>> > + This property is unordered, and MSIs may be allocated from any combination of
>> > + MSI controllers listed in the msi-parent property.
>> > +
>> > + If a device has restrictions on the allocation of MSIs, these restrictions
>> > + must be described with additional properties.
>> > +
>> > + When #msi-cells is non-zero, busses with an msi-parent will require
>> > + additional properties to describe the relationship between devices on the bus
>> > + and the set of MSIs they can potentially generate.
>> > +
>> > +
>> > +Example
>> > +=======
>> > +
>> > +/ {
>> > + #address-cells = <1>;
>> > + #size-cells = <1>;
>> > +
>> > + msi_a: msi-controller at a {
>> > + reg = <0xa 0xf00>;
>> > + compatible = "vendor-a,some-controller";
>> > + msi-controller;
>> > + /* No sideband data, so #msi-cells omitted */
>> > + };
>> > +
>> > + msi_b: msi-controller at b {
>> > + reg = <0xb 0xf00>;
>> > + compatible = "vendor-b,another-controller";
>> > + msi-controller;
>> > + /* Each device has some unique ID */
>> > + #msi-cells = <1>;
>> > + };
>> > +
>> > + msi_c: msi-controller at c {
>> > + reg = <0xb 0xf00>;
>> > + compatible = "vendor-b,another-controller";
>> > + msi-controller;
>> > + /* Each device has some unique ID */
>> > + #msi-cells = <1>;
>> > + };
>> > +
>> > + dev at 0 {
>> > + reg = <0x0 0xf00>;
>> > + compatible = "vendor-c,some-device";
>> > +
>> > + /* Can only generate MSIs to msi_a */
>> > + msi-parent = <&msi_a>;
>> > + };
>> > +
>> > + dev at 1 {
>> > + reg = <0x1 0xf00>;
>> > + compatible = "vendor-c,some-device";
>> > +
>> > + /*
>> > + * Can generate MSIs to either A or B.
>> > + */
>> > + msi-parent = <&msi_a>, <&msi_b 0x17>;
>> > + };
>> > +
>> > + dev at 2 {
>> > + reg = <0x2 0xf00>;
>> > + compatible = "vendor-c,some-device";
>> > + /*
>> > + * Has different IDs at each MSI controller.
>> > + * Can generate MSIs to all of the MSI controllers.
>> > + */
>> > + msi-parent = <&msi_a>, <&msi_b 0x17>, <&msi_c 0x53>;
>> > + };
>> > +};
>> > --
>> > 1.9.1
>> >
>> --
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