Patch adds a device tree function to detect the nest pmu
support. Function will look for specific dt property "ibm,ima-chip"
as a detection mechanism for the nest pmu.

For Nest pmu, device tree will have two set of information.
1) Per-chip Homer address region for nest pmu counter collection area.
2) Supported Nest PMUs and events

Device tree layout for the Nest PMU as follows.

  /                     -- DT root folder
  |
  -nest-ima             -- Nest PMU folder
   |

   -ima-chip@<chip-id>  -- Per-chip folder for HOMER region information
    |
    -ibm,chip-id        -- Chip id
    -ibm,ima-chip
    -reg                -- HOMER PORE Nest Counter collection Address (RA)
    -size               -- size to map in kernel space

   -Alink_BW            -- Nest PMU folder
    |
    -Alink0             -- Nest PMU Alink Event file
    -scale.Alink0.scale -- Event scale file
    -unit.Alink0.unit   -- Event unit file
    -device_type        -- "nest-ima-unit" marker
  ....

Patch save per-chip HOMER offset and maps the same to kernel structure.
Subsequent patch will parse the next part of the DT to find various
Nest PMUs and their events.

Cc: Michael Ellerman <m...@ellerman.id.au>
Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org>
Cc: Paul Mackerras <pau...@samba.org>
Cc: Sukadev Bhattiprolu <suka...@linux.vnet.ibm.com>
Cc: Anshuman Khandual <khand...@linux.vnet.ibm.com>
Cc: Stephane Eranian <eran...@google.com>
Signed-off-by: Madhavan Srinivasan <ma...@linux.vnet.ibm.com>
---
 arch/powerpc/perf/nest-pmu.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/arch/powerpc/perf/nest-pmu.c b/arch/powerpc/perf/nest-pmu.c
index 345707c..c979e57 100644
--- a/arch/powerpc/perf/nest-pmu.c
+++ b/arch/powerpc/perf/nest-pmu.c
@@ -11,6 +11,7 @@
 
 #include "nest-pmu.h"
 
+static struct perchip_nest_info p8_perchip_nest_info[P8_MAX_CHIP];
 static cpumask_t cpu_mask_nest_pmu;
 
 static ssize_t cpumask_nest_pmu_get_attr(struct device *dev,
@@ -242,6 +243,36 @@ static int update_pmu_ops(struct nest_pmu *pmu)
        return 0;
 }
 
+static int nest_ima_detect_parse(void)
+{
+       const __be32 *gcid;
+       const __be64 *chip_ima_reg;
+       const __be64 *chip_ima_size;
+       struct device_node *dev;
+       int rc = -EINVAL, idx;
+
+       for_each_node_with_property(dev, "ibm,ima-chip") {
+               gcid = of_get_property(dev, "ibm,chip-id", NULL);
+               chip_ima_reg = of_get_property(dev, "reg", NULL);
+               chip_ima_size = of_get_property(dev, "size", NULL);
+               if ((!gcid) || (!chip_ima_reg) || (!chip_ima_size)) {
+                       pr_err("%s: device %s missing property \n",
+                               __func__, dev->full_name);
+                       return rc;
+               }
+
+               idx = (uint32_t)be32_to_cpup(gcid);
+               p8_perchip_nest_info[idx].pbase = be64_to_cpup(chip_ima_reg);
+               p8_perchip_nest_info[idx].size = be64_to_cpup(chip_ima_size);
+               p8_perchip_nest_info[idx].vbase = (uint64_t)
+                       phys_to_virt(p8_perchip_nest_info[idx].pbase);
+
+               rc = 0;
+       }
+
+       return rc;
+}
+
 static int __init nest_pmu_init(void)
 {
        int ret = 0;
@@ -256,6 +287,12 @@ static int __init nest_pmu_init(void)
 
        cpumask_chip();
 
+       /*
+        * Detect the Nest PMU feature
+        */
+       if (nest_ima_detect_parse())
+               return 0;
+
        return 0;
 }
 device_initcall(nest_pmu_init);
-- 
1.9.1

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