[PATCH v3 2/2] drivers/irqchip: gicv3: add workaround for Synquacer pre-ITS

On 12 October 2017 at 22:34, Rob Herring [off-list ref] wrote:

On Thu, Oct 12, 2017 at 1:32 PM, Ard Biesheuvel
[off-list ref] wrote:

quoted

The Socionext Synquacer SoC's implementation of GICv3 has a so-called
'pre-ITS', which maps 32-bit writes targeted at a separate window of
size '4 << device_id_bits' onto writes to GITS_TRANSLATER with device
ID taken from bits [device_id_bits + 1:2] of the window offset.
Writes that target GITS_TRANSLATER directly are reported as originating
from device ID #0.

So add a workaround for this. Given that this breaks isolation, clear
the IRQ_DOMAIN_FLAG_MSI_REMAP flag as well.

Signed-off-by: Ard Biesheuvel <redacted>
---
 Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt |  4 ++
 arch/arm64/Kconfig                                                    |  8 +++
 drivers/irqchip/irq-gic-v3-its.c                                      | 63 +++++++++++++++++++-
 3 files changed, 72 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt b/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt
index 4c29cdab0ea5..0798a61bbf99 100644
--- a/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt
+++ b/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt

@@ -75,6 +75,10 @@ These nodes must have the following properties:
 - reg: Specifies the base physical address and size of the ITS
   registers.

+Optional:
+- socionext,synquacer-pre-its: (u32, u32) tuple describing the host address
+  and size of the pre-ITS window, as implemented on the Socionext Synquacer SoC

Sounds like a separate h/w block to me and addresses should be in
"reg". I would suggest you define a separate node for the pre-its
block and then use of_find_compatible_node() from the GIC driver to
retrieve the node and whatever you need from it. Or do an SoC specific
compatible string for the GIC and let that imply whatever information
you need. Then the next quirk doesn't need a DT update.

For my understanding, you mean either

    gic: interrupt-controller at 30000000 {
        compatible = "arm,gic-v3";
        ...

        its: gic-its at 30020000 {
            compatible = "arm,gic-v3-its";
            reg = <0x0 0x30020000 0x0 0x20000>;
            #msi-cells = <1>;
            msi-controller;
        };
    };

    preits at 58000000 {
        compatible = "socionext,synquacer-pre-its";
        reg = <0x0 0x58000000 0x0 0x200000>;
        msi-slave = <&its>;
    };

or

    gic: interrupt-controller at 30000000 {
        compatible = "arm,gic-v3";
        ...

        its: gic-its at 30020000 {
            compatible = "socionext,synquacer-pre-its", "arm,gic-v3-its";
            reg = <0x0 0x30020000 0x0 0x20000>,
                  <0x0 0x58000000 0x0 0x200000>;
            #msi-cells = <1>;
            msi-controller;
        };
    };

right?

Marc, what do you think? IIRC we did discuss option #2 at some point,
but I don't remember if/why we rejected it.