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Subject[Patch v4 3/3] platform/x86: intel_pmc_core: Decode Snoop / Non Snoop LTR
Date
The LTR values follow PCIE LTR encoding format and can be decoded as per
https://pcisig.com/sites/default/files/specification_documents/ECN_LatencyTolnReporting_14Aug08.pdf

This adds support to translate the raw LTR values as read from the PMC
to meaningful values in nanosecond units of time.

Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@linux.intel.com>
---
Changes in v4:
* Moved bits.h include to intel_pmc_core.h
* Reordered LTR related #defines in increasing manner.

drivers/platform/x86/intel_pmc_core.c | 62 ++++++++++++++++++++++++++-
drivers/platform/x86/intel_pmc_core.h | 7 +++
2 files changed, 67 insertions(+), 2 deletions(-)

diff --git a/drivers/platform/x86/intel_pmc_core.c b/drivers/platform/x86/intel_pmc_core.c
index 0c18f328cd0d..eba6f5c27e2f 100644
--- a/drivers/platform/x86/intel_pmc_core.c
+++ b/drivers/platform/x86/intel_pmc_core.c
@@ -12,6 +12,7 @@
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/acpi.h>
+#include <linux/bitfield.h>
#include <linux/debugfs.h>
#include <linux/delay.h>
#include <linux/io.h>
@@ -638,15 +639,72 @@ static int pmc_core_slps0_dbg_show(struct seq_file *s, void *unused)
}
DEFINE_SHOW_ATTRIBUTE(pmc_core_slps0_dbg);

+static u32 convert_ltr_scale(u32 val)
+{
+ /*
+ * As per PCIE specification supporting document
+ * ECN_LatencyTolnReporting_14Aug08.pdf the Latency
+ * Tolerance Reporting data payload is encoded in a
+ * 3 bit scale and 10 bit value fields. Values are
+ * multiplied by the indicated scale to yield an absolute time
+ * value, expressible in a range from 1 nanosecond to
+ * 2^25*(2^10-1) = 34,326,183,936 nanoseconds.
+ *
+ * scale encoding is as follows:
+ *
+ * ----------------------------------------------
+ * |scale factor | Multiplier (ns) |
+ * ----------------------------------------------
+ * | 0 | 1 |
+ * | 1 | 32 |
+ * | 2 | 1024 |
+ * | 3 | 32768 |
+ * | 4 | 1048576 |
+ * | 5 | 33554432 |
+ * | 6 | Invalid |
+ * | 7 | Invalid |
+ * ----------------------------------------------
+ */
+ if (val > 5) {
+ pr_warn("Invalid LTR scale factor.\n");
+ return 0;
+ }
+
+ return 1U << (5 * val);
+}
+
static int pmc_core_ltr_show(struct seq_file *s, void *unused)
{
struct pmc_dev *pmcdev = s->private;
const struct pmc_bit_map *map = pmcdev->map->ltr_show_sts;
+ u64 decoded_snoop_ltr, decoded_non_snoop_ltr;
+ u32 ltr_raw_data, scale, val;
+ u16 snoop_ltr, nonsnoop_ltr;
int index;

for (index = 0; map[index].name ; index++) {
- seq_printf(s, "%-32s\tRAW LTR: 0x%x\n", map[index].name,
- pmc_core_reg_read(pmcdev, map[index].bit_mask));
+ decoded_snoop_ltr = decoded_non_snoop_ltr = 0;
+ ltr_raw_data = pmc_core_reg_read(pmcdev,
+ map[index].bit_mask);
+ snoop_ltr = ltr_raw_data & ~MTPMC_MASK;
+ nonsnoop_ltr = (ltr_raw_data >> 0x10) & ~MTPMC_MASK;
+
+ if (FIELD_GET(LTR_REQ_NONSNOOP, ltr_raw_data)) {
+ scale = FIELD_GET(LTR_DECODED_SCALE, nonsnoop_ltr);
+ val = FIELD_GET(LTR_DECODED_VAL, nonsnoop_ltr);
+ decoded_non_snoop_ltr = val * convert_ltr_scale(scale);
+ }
+
+ if (FIELD_GET(LTR_REQ_SNOOP, ltr_raw_data)) {
+ scale = FIELD_GET(LTR_DECODED_SCALE, snoop_ltr);
+ val = FIELD_GET(LTR_DECODED_VAL, snoop_ltr);
+ decoded_snoop_ltr = val * convert_ltr_scale(scale);
+ }
+
+ seq_printf(s, "%-32s\tLTR: RAW: 0x%-16x\tNon-Snoop(ns): %-16llu\tSnoop(ns): %-16llu\n",
+ map[index].name, ltr_raw_data,
+ decoded_non_snoop_ltr,
+ decoded_snoop_ltr);
}
return 0;
}
diff --git a/drivers/platform/x86/intel_pmc_core.h b/drivers/platform/x86/intel_pmc_core.h
index e57b26cdb442..89554cba5758 100644
--- a/drivers/platform/x86/intel_pmc_core.h
+++ b/drivers/platform/x86/intel_pmc_core.h
@@ -12,6 +12,8 @@
#ifndef PMC_CORE_H
#define PMC_CORE_H

+#include <linux/bits.h>
+
#define PMC_BASE_ADDR_DEFAULT 0xFE000000

/* Sunrise Point Power Management Controller PCI Device ID */
@@ -169,6 +171,11 @@ enum ppfear_regs {
#define CNP_PMC_LTR_EMMC 0x1BF4
#define CNP_PMC_LTR_UFSX2 0x1BF8

+#define LTR_DECODED_VAL GENMASK(9, 0)
+#define LTR_DECODED_SCALE GENMASK(12, 10)
+#define LTR_REQ_SNOOP BIT(15)
+#define LTR_REQ_NONSNOOP BIT(31)
+
struct pmc_bit_map {
const char *name;
u32 bit_mask;
--
2.17.1
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