patch 'power/amd_pstate: fix frequency matching on init' has been queued to stable release 24.11.9

[luca.boccassi at gmail.com]

Hi,

FYI, your patch has been queued to stable release 24.11.9

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 10/29/26. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/bluca/dpdk-stable

This queued commit can be viewed at:
https://github.com/bluca/dpdk-stable/commit/3a14ef3447c130caa3b0f4bf151a545372e27509

Thanks.

Luca Boccassi

---
>From 3a14ef3447c130caa3b0f4bf151a545372e27509 Mon Sep 17 00:00:00 2001
From: Stephen Hemminger <stephen at networkplumber.org>
Date: Tue, 8 Sep 2026 09:52:32 -0700
Subject: [PATCH] power/amd_pstate: fix frequency matching on init

[ upstream commit 8e25148a7a016112ae2f52c6dade53bfdf475e5b ]

power_init_for_setting_freq() fails with the amd-pstate driver because
the frequency read from scaling_setspeed does not exactly match any of
the synthesized frequency buckets. Unlike acpi_cpufreq, which provides a
discrete list, amd-pstate scales continuously, so an exact match rarely
succeeds. On a Ryzen 9 7945HX the sysfs file reports 2492000 while the
buckets are spaced by (scaling_max - scaling_min) / 63.

Use the nearest frequency instead of an exact match.

Since the match is only the nearest bucket, curr_idx would no longer
match what was last written to scaling_setspeed. set_freq_internal()
returns early when the requested index is already current, so setting
that bucket would report success without doing anything. Split the
sysfs write out into write_freq() and program the bucket during init.

Also in the same function:
 - strtoul() was called with NULL endptr, so parse failures went
   undetected
 - errno was not checked
 - freq was uint32_t, truncating the strtoul() result on LP64
 - no error was logged when matching failed

Bugzilla ID: 1915
Fixes: 1ed04d33cf19 ("power: support amd-pstate cpufreq driver")

Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
Acked-by: Sivaprasad Tummala <sivaprasad.tummala at amd.com>
---
 drivers/power/amd_pstate/amd_pstate_cpufreq.c | 91 +++++++++++++------
 1 file changed, 63 insertions(+), 28 deletions(-)

diff --git a/drivers/power/amd_pstate/amd_pstate_cpufreq.c b/drivers/power/amd_pstate/amd_pstate_cpufreq.c
index 95495bff7db..97e179b7eef 100644
--- a/drivers/power/amd_pstate/amd_pstate_cpufreq.c
+++ b/drivers/power/amd_pstate/amd_pstate_cpufreq.c
@@ -5,6 +5,7 @@
  */
 
 #include <stdlib.h>
+#include <errno.h>
 
 #include <rte_memcpy.h>
 #include <rte_stdatomic.h>
@@ -62,6 +63,25 @@ struct __rte_cache_aligned amd_pstate_power_info {
 
 static struct amd_pstate_power_info lcore_power_info[RTE_MAX_LCORE];
 
+static int
+write_freq(struct amd_pstate_power_info *pi, uint32_t idx)
+{
+	if (fseek(pi->f, 0, SEEK_SET) < 0) {
+		POWER_LOG(ERR, "Fail to set file position indicator to 0 "
+			"for setting frequency for lcore %u", pi->lcore_id);
+		return -1;
+	}
+	if (fprintf(pi->f, "%u", pi->freqs[idx]) < 0) {
+		POWER_LOG(ERR, "Fail to write new frequency for "
+				"lcore %u", pi->lcore_id);
+		return -1;
+	}
+	fflush(pi->f);
+	pi->curr_idx = idx;
+
+	return 1;
+}
+
 /**
  * It is to set specific freq for specific logical core, according to the index
  * of supported frequencies.
@@ -81,20 +101,8 @@ set_freq_internal(struct amd_pstate_power_info *pi, uint32_t idx)
 
 	POWER_DEBUG_LOG("Frequency[%u] %u to be set for lcore %u",
 			idx, pi->freqs[idx], pi->lcore_id);
-	if (fseek(pi->f, 0, SEEK_SET) < 0) {
-		POWER_LOG(ERR, "Fail to set file position indicator to 0 "
-			"for setting frequency for lcore %u", pi->lcore_id);
-		return -1;
-	}
-	if (fprintf(pi->f, "%u", pi->freqs[idx]) < 0) {
-		POWER_LOG(ERR, "Fail to write new frequency for "
-				"lcore %u", pi->lcore_id);
-		return -1;
-	}
-	fflush(pi->f);
-	pi->curr_idx = idx;
 
-	return 1;
+	return write_freq(pi, idx);
 }
 
 /**
@@ -291,15 +299,21 @@ out:
 	return ret;
 }
 
-/**
- * It is to fopen the sys file for the future setting the lcore frequency.
- */
+static inline unsigned long
+abs_diff(unsigned long a, unsigned long b)
+{
+	return (a > b) ? a - b : b - a;
+}
+
 static int
 power_init_for_setting_freq(struct amd_pstate_power_info *pi)
 {
-	FILE *f = NULL;
+	FILE *f;
 	char buf[BUFSIZ];
-	uint32_t i, freq;
+	char *endptr;
+	unsigned long freq, freq_conv;
+	unsigned long best_diff, diff;
+	uint32_t i, best_idx;
 	int ret;
 
 	open_core_sysfs_file(&f, "rw+", POWER_SYSFILE_SETSPEED, pi->lcore_id);
@@ -308,7 +322,6 @@ power_init_for_setting_freq(struct amd_pstate_power_info *pi)
 				POWER_SYSFILE_SETSPEED);
 		goto err;
 	}
-
 	ret = read_core_sysfs_s(f, buf, sizeof(buf));
 	if (ret < 0) {
 		POWER_LOG(ERR, "Failed to read %s",
@@ -316,28 +329,50 @@ power_init_for_setting_freq(struct amd_pstate_power_info *pi)
 		goto err;
 	}
 
-	freq = strtoul(buf, NULL, POWER_CONVERT_TO_DECIMAL);
+	errno = 0;
+	freq = strtoul(buf, &endptr, POWER_CONVERT_TO_DECIMAL);
+	if (errno != 0 || endptr == buf || freq == 0) {
+		POWER_LOG(ERR, "Failed to parse frequency '%s' for lcore %u",
+				buf, pi->lcore_id);
+		goto err;
+	}
 
 	/* convert the frequency to nearest 1000 value
 	 * Ex: if freq=1396789 then freq_conv=1397000
 	 * Ex: if freq=800030 then freq_conv=800000
 	 */
-	unsigned int freq_conv = 0;
-	freq_conv = (freq + FREQ_ROUNDING_DELTA)
-				/ ROUND_FREQ_TO_N_1000;
+	freq_conv = (freq + FREQ_ROUNDING_DELTA) / ROUND_FREQ_TO_N_1000;
 	freq_conv = freq_conv * ROUND_FREQ_TO_N_1000;
 
-	for (i = 0; i < pi->nb_freqs; i++) {
-		if (freq_conv == pi->freqs[i]) {
-			pi->curr_idx = i;
-			pi->f = f;
-			return 0;
+	/* amd-pstate scales continuously, so the current frequency will
+	 * rarely match a bucket exactly. Use the nearest one.
+	 */
+	best_idx = 0;
+	best_diff = abs_diff(freq_conv, pi->freqs[0]);
+
+	for (i = 1; i < pi->nb_freqs; i++) {
+		diff = abs_diff(freq_conv, pi->freqs[i]);
+		if (diff < best_diff) {
+			best_diff = diff;
+			best_idx = i;
 		}
 	}
 
+	POWER_DEBUG_LOG("Freq %lu rounded to %lu matched bucket [%u] = %u "
+			"for lcore %u", freq, freq_conv, best_idx,
+			pi->freqs[best_idx], pi->lcore_id);
+
+	/* Program the bucket so curr_idx matches the actual frequency. */
+	pi->f = f;
+	if (write_freq(pi, best_idx) < 0)
+		goto err;
+
+	return 0;
+
 err:
 	if (f != NULL)
 		fclose(f);
+	pi->f = NULL;
 
 	return -1;
 }
-- 
2.47.3

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2026-10-27 11:43:58.470506521 +0000
+++ 0123-power-amd_pstate-fix-frequency-matching-on-init.patch	2026-10-27 11:43:53.650063658 +0000
@@ -1 +1 @@
-From 8e25148a7a016112ae2f52c6dade53bfdf475e5b Mon Sep 17 00:00:00 2001
+From 3a14ef3447c130caa3b0f4bf151a545372e27509 Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit 8e25148a7a016112ae2f52c6dade53bfdf475e5b ]
+
@@ -30 +31,0 @@
-Cc: stable at dpdk.org
@@ -39 +40 @@
-index af9c1309f3..13ffcefc84 100644
+index 95495bff7db..97e179b7eef 100644
@@ -50 +51 @@
-@@ -53,6 +54,25 @@ struct __rte_cache_aligned amd_pstate_power_info {
+@@ -62,6 +63,25 @@ struct __rte_cache_aligned amd_pstate_power_info {
@@ -76 +77 @@
-@@ -72,20 +92,8 @@ set_freq_internal(struct amd_pstate_power_info *pi, uint32_t idx)
+@@ -81,20 +101,8 @@ set_freq_internal(struct amd_pstate_power_info *pi, uint32_t idx)
@@ -98 +99 @@
-@@ -282,15 +290,21 @@ out:
+@@ -291,15 +299,21 @@ out:
@@ -125 +126 @@
-@@ -299,7 +313,6 @@ power_init_for_setting_freq(struct amd_pstate_power_info *pi)
+@@ -308,7 +322,6 @@ power_init_for_setting_freq(struct amd_pstate_power_info *pi)
@@ -133 +134 @@
-@@ -307,28 +320,50 @@ power_init_for_setting_freq(struct amd_pstate_power_info *pi)
+@@ -316,28 +329,50 @@ power_init_for_setting_freq(struct amd_pstate_power_info *pi)