Re: [PATCH 3/4] arm_pmu: acpi: spe: Add initial MADT/SPE probing

From: Jeremy Linton
Date: Tue Apr 02 2019 - 15:14:34 EST


Hi,

First thanks for taking a look at this, second sorry about the delay...

On 3/28/19 7:40 AM, John Garry wrote:
On 26/03/2019 22:39, Jeremy Linton wrote:
ACPI 6.3 adds additional fields to the MADT GICC
structure to describe SPE PPI's. We pick these out
of the cached reference to the madt_gicc structure
similarly to the core PMU code. We then create a platform
device referring to the IRQ and let the user/module loader
decide whether to load the SPE driver.

Signed-off-by: Jeremy Linton <jeremy.linton@xxxxxxx>
---
 arch/arm64/include/asm/acpi.h |  3 ++
 drivers/perf/arm_pmu_acpi.c   | 69 +++++++++++++++++++++++++++++++++++
 2 files changed, 72 insertions(+)

diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
index 7628efbe6c12..d10399b9f998 100644
--- a/arch/arm64/include/asm/acpi.h
+++ b/arch/arm64/include/asm/acpi.h
@@ -41,6 +41,9 @@
     (!(entry) || (entry)->header.length < ACPI_MADT_GICC_MIN_LENGTH || \
     (unsigned long)(entry) + (entry)->header.length > (end))

+#define ACPI_MADT_GICC_SPE  (ACPI_OFFSET(struct acpi_madt_generic_interrupt, \
+    spe_interrupt) + sizeof(u16))
+
 /* Basic configuration for ACPI */
 #ifdef    CONFIG_ACPI
 pgprot_t __acpi_get_mem_attribute(phys_addr_t addr);
diff --git a/drivers/perf/arm_pmu_acpi.c b/drivers/perf/arm_pmu_acpi.c
index 0f197516d708..a2418108eab2 100644
--- a/drivers/perf/arm_pmu_acpi.c
+++ b/drivers/perf/arm_pmu_acpi.c
@@ -74,6 +74,73 @@ static void arm_pmu_acpi_unregister_irq(int cpu)
     acpi_unregister_gsi(gsi);
 }

+static struct resource spe_resources[] = {
+    {
+        /* irq */
+        .flags          = IORESOURCE_IRQ,
+    }
+};
+
+static struct platform_device spe_dev = {
+    .name = "arm,spe-v1",
+    .id = -1,
+    .resource = spe_resources,
+    .num_resources = ARRAY_SIZE(spe_resources)
+};
+
+/*
+ * For lack of a better place,

It seems that the kernel Image size can now increase due to this part of SPE support even if ARM_SPE_PMU config is disabled.

That is true, but it should be fairly small.


And I don't even think that ARM_SPE_PMU depends on ARM_PMU (which ARM_PMU_ACPI depends on).

Well I don't think we want the generic SPE_PMU dependent on ACPI. So this chunk of code could be wrapped in a SPE_PMU_ACPI block, and made dependent on PMU_ACPI. OTOH, It seems a little trivial for that, and maybe just tweaking the PMU_ACPI documentation to mention that it also enables ACPI/SPE is a better plan.

Opinions?



Thanks,
John

hook the normal PMU MADT walk
+ * and create a SPE device if we detect a recent MADT with
+ * a homogeneous PPI mapping.
+ */
+static int arm_spe_acpi_parse_irqs(void)
+{
+    int cpu, ret, irq;
+    int hetid;
+    u16 gsi = 0;
+    bool first = true;
+
+    struct acpi_madt_generic_interrupt *gicc;
+
+    /*
+     * sanity check all the GICC tables for the same interrupt number
+     * for now we only support homogeneous ACPI/SPE machines.
+     */
+    for_each_possible_cpu(cpu) {
+        gicc = acpi_cpu_get_madt_gicc(cpu);
+
+        if (gicc->header.length < ACPI_MADT_GICC_SPE)
+            return -ENODEV;
+        if (first) {
+            gsi = gicc->spe_interrupt;
+            if (!gsi)
+                return -ENODEV;
+            hetid = find_acpi_cpu_topology_hetero_id(cpu);
+            first = false;
+        } else if ((gsi != gicc->spe_interrupt) ||
+               (hetid != find_acpi_cpu_topology_hetero_id(cpu))) {
+            pr_warn("ACPI: SPE must be homogeneous\n");
+            return -EINVAL;
+        }
+    }
+
+    irq = acpi_register_gsi(NULL, gsi, ACPI_LEVEL_SENSITIVE,
+                ACPI_ACTIVE_HIGH);
+    if (irq < 0) {
+        pr_warn("ACPI: SPE Unable to register interrupt: %d\n", gsi);
+        return irq;
+    }
+
+    spe_resources[0].start = irq;
+    ret = platform_device_register(&spe_dev);
+    if (ret < 0) {
+        pr_warn("ACPI: SPE: Unable to register device\n");
+        acpi_unregister_gsi(gsi);
+    }
+
+    return ret;
+}
+
 static int arm_pmu_acpi_parse_irqs(void)
 {
     int irq, cpu, irq_cpu, err;
@@ -279,6 +346,8 @@ static int arm_pmu_acpi_init(void)
     if (acpi_disabled)
         return 0;

+    arm_spe_acpi_parse_irqs(); /* failures are expected */
+
     ret = arm_pmu_acpi_parse_irqs();
     if (ret)
         return ret;