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

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
+
 The main GIC node must contain the appropriate #address-cells,
 #size-cells and ranges properties for the reg property of all ITS
 nodes.

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 0df64a6a56d4..c4361dff2b74 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig

@@ -539,6 +539,14 @@ config QCOM_QDF2400_ERRATUM_0065

          If unsure, say Y.

+config SOCIONEXT_SYNQUACER_PREITS
+       bool "Socionext Synquacer: Workaround for GICv3 pre-ITS"
+       default y
+       help
+         Socionext Synquacer SoCs implement a separate h/w block to generate
+         MSI doorbell writes with non-zero values for the device ID.
+
+         If unsure, say Y.
 endmenu

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 891de07fd4cc..2fc4fba0cc4c 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c

@@ -97,12 +97,18 @@ struct its_node {
        struct its_cmd_block    *cmd_write;
        struct its_baser        tables[GITS_BASER_NR_REGS];
        struct its_collection   *collections;
+       struct fwnode_handle    *fwnode_handle;
        struct list_head        its_device_list;
        u64                     flags;
        u32                     ite_size;
        u32                     device_ids;
        int                     numa_node;
+       unsigned int            msi_domain_flag_mask;
        bool                    is_v4;
+
+       /* for Socionext Synquacer pre-ITS */
+       u32                     pre_its_base;
+       u32                     pre_its_size;
 };

 #define ITS_ITT_ALIGN          SZ_256

@@ -1095,14 +1101,29 @@ static int its_set_affinity(struct irq_data *d, const struct cpumask *mask_val,
        return IRQ_SET_MASK_OK_DONE;
 }

+static u64 its_irq_get_msi_base(struct its_device *its_dev)
+{
+       struct its_node *its = its_dev->its;
+
+       if (unlikely(its->pre_its_size > 0))
+               /*
+                * The Socionext Synquacer SoC 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.
+                */
+               return its->pre_its_base + (its_dev->device_id << 2);
+
+       return its->phys_base + GITS_TRANSLATER;
+}
+
 static void its_irq_compose_msi_msg(struct irq_data *d, struct msi_msg *msg)
 {
        struct its_device *its_dev = irq_data_get_irq_chip_data(d);
-       struct its_node *its;
        u64 addr;

-       its = its_dev->its;
-       addr = its->phys_base + GITS_TRANSLATER;
+       addr = its_irq_get_msi_base(its_dev);

        msg->address_lo         = lower_32_bits(addr);
        msg->address_hi         = upper_32_bits(addr);

@@ -2752,6 +2773,27 @@ static void __maybe_unused its_enable_quirk_qdf2400_e0065(void *data)
        its->ite_size = 16;
 }

+static void __maybe_unused its_enable_quirk_socionext_synquacer(void *data)
+{
+       struct its_node *its = data;
+       u32 pre_its_window[2];
+       u32 ids;
+
+       if (!fwnode_property_read_u32_array(its->fwnode_handle,
+                                           "socionext,synquacer-pre-its",
+                                           pre_its_window,
+                                           ARRAY_SIZE(pre_its_window))) {
+               its->pre_its_base = pre_its_window[0];
+               its->pre_its_size = pre_its_window[1];
+
+               ids = ilog2(its->pre_its_size) - 2;
+               if (its->device_ids > ids)
+                       its->device_ids = ids;
+
+               its->msi_domain_flag_mask = ~IRQ_DOMAIN_FLAG_MSI_REMAP;
+       }
+}
+
 static const struct gic_quirk its_quirks[] = {
 #ifdef CONFIG_CAVIUM_ERRATUM_22375
        {

@@ -2777,6 +2819,19 @@ static const struct gic_quirk its_quirks[] = {
                .init   = its_enable_quirk_qdf2400_e0065,
        },
 #endif
+#ifdef CONFIG_SOCIONEXT_SYNQUACER_PREITS
+       {
+               /*
+                * The Socionext Synquacer SoC incorporates ARM's own GIC-500
+                * implementation, but with a 'pre-ITS' added that requires
+                * special handling in software.
+                */
+               .desc   = "ITS: Socionext Synquacer pre-ITS",
+               .iidr   = 0x0001143b,
+               .mask   = 0xffffffff,
+               .init   = its_enable_quirk_socionext_synquacer,
+       },
+#endif
        {
        }
 };

@@ -2806,6 +2861,7 @@ static int its_init_domain(struct fwnode_handle *handle, struct its_node *its)
        inner_domain->parent = its_parent;
        irq_domain_update_bus_token(inner_domain, DOMAIN_BUS_NEXUS);
        inner_domain->flags |= IRQ_DOMAIN_FLAG_MSI_REMAP;
+       inner_domain->flags &= its->msi_domain_flag_mask;

        info->ops = &its_msi_domain_ops;
        info->data = its;
        inner_domain->host_data = info;

@@ -2959,6 +3015,7 @@ static int __init its_probe_one(struct resource *res,
                goto out_free_its;
        }
        its->cmd_write = its->cmd_base;
+       its->fwnode_handle = handle;

        its_enable_quirks(its);

--

2.11.0