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mediatek: don't let devfreq power-off the CPU

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Fix a long standing bug in the mediatek-cci-devfreq driver which leads
to the driver switching off the CPU power regulator in case of another
resource not being ready in time -- a classic probe-order race condition.

As a work-around it would of course just as well be possible to set the
CPU regulator as 'regulator-always-on' (and not just 'regulator-boot-on'),
but practically all MT7988 devices have copy&pasted the PMIC device tree
hunk which sets only 'regulator-boot-on').

Hence, in order not having to fix all device trees, a proper fix in the
driver is preferred.

Fixes: #683
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
This commit is contained in:
Daniel Golle 2026-04-11 22:59:07 +01:00
parent ca8d931205
commit a45ce4c788
2 changed files with 294 additions and 0 deletions
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241
target/linux/mediatek/patches-6.12/210-PM-devfreq-mtk-cci-use-devres-for-resource-managemen.patch Normal file
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@ -0,0 +1,241 @@
From b61fcc3c7f95734e14741d8787fc9eb69b8437d4 Mon Sep 17 00:00:00 2001
From: Daniel Golle <daniel@makrotopia.org>
Date: Sat, 11 Apr 2026 22:47:15 +0100
Subject: [PATCH 1/2] PM / devfreq: mtk-cci: use devres for resource management
in probe
Convert mtk_ccifreq_probe() to use devm-managed resource cleanup
instead of manual goto-based error handling.
This pattern (devm_add_action_or_reset with a regulator disable
callback) is well-established in the kernel, used by drivers such as
ads7846, max6639 and others.
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
drivers/devfreq/mtk-cci-devfreq.c | 150 +++++++++++++++---------------
1 file changed, 73 insertions(+), 77 deletions(-)
--- a/drivers/devfreq/mtk-cci-devfreq.c
+++ b/drivers/devfreq/mtk-cci-devfreq.c
@@ -246,6 +246,21 @@ static struct devfreq_dev_profile mtk_cc
.target = mtk_ccifreq_target,
};
+static void mtk_ccifreq_regulator_disable(void *data)
+{
+ regulator_disable(data);
+}
+
+static void mtk_ccifreq_clk_disable_unprepare(void *data)
+{
+ clk_disable_unprepare(data);
+}
+
+static void mtk_ccifreq_opp_of_remove_table(void *data)
+{
+ dev_pm_opp_of_remove_table(data);
+}
+
static int mtk_ccifreq_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
@@ -266,44 +281,47 @@ static int mtk_ccifreq_probe(struct plat
platform_set_drvdata(pdev, drv);
drv->cci_clk = devm_clk_get(dev, "cci");
- if (IS_ERR(drv->cci_clk)) {
- ret = PTR_ERR(drv->cci_clk);
- return dev_err_probe(dev, ret, "failed to get cci clk\n");
- }
+ if (IS_ERR(drv->cci_clk))
+ return dev_err_probe(dev, PTR_ERR(drv->cci_clk),
+ "failed to get cci clk\n");
drv->inter_clk = devm_clk_get(dev, "intermediate");
- if (IS_ERR(drv->inter_clk)) {
- ret = PTR_ERR(drv->inter_clk);
- return dev_err_probe(dev, ret,
+ if (IS_ERR(drv->inter_clk))
+ return dev_err_probe(dev, PTR_ERR(drv->inter_clk),
"failed to get intermediate clk\n");
- }
drv->proc_reg = devm_regulator_get_optional(dev, "proc");
- if (IS_ERR(drv->proc_reg)) {
- ret = PTR_ERR(drv->proc_reg);
- return dev_err_probe(dev, ret,
+ if (IS_ERR(drv->proc_reg))
+ return dev_err_probe(dev, PTR_ERR(drv->proc_reg),
"failed to get proc regulator\n");
- }
ret = regulator_enable(drv->proc_reg);
- if (ret) {
- dev_err(dev, "failed to enable proc regulator\n");
+ if (ret)
+ return dev_err_probe(dev, ret,
+ "failed to enable proc regulator\n");
+
+ ret = devm_add_action_or_reset(dev, mtk_ccifreq_regulator_disable,
+ drv->proc_reg);
+ if (ret)
return ret;
- }
drv->sram_reg = devm_regulator_get_optional(dev, "sram");
if (IS_ERR(drv->sram_reg)) {
- ret = PTR_ERR(drv->sram_reg);
- if (ret == -EPROBE_DEFER)
- goto out_free_resources;
+ if (PTR_ERR(drv->sram_reg) == -EPROBE_DEFER)
+ return -EPROBE_DEFER;
drv->sram_reg = NULL;
} else {
ret = regulator_enable(drv->sram_reg);
- if (ret) {
- dev_err(dev, "failed to enable sram regulator\n");
- goto out_free_resources;
- }
+ if (ret)
+ return dev_err_probe(dev, ret,
+ "failed to enable sram regulator\n");
+
+ ret = devm_add_action_or_reset(dev,
+ mtk_ccifreq_regulator_disable,
+ drv->sram_reg);
+ if (ret)
+ return ret;
}
/*
@@ -317,31 +335,36 @@ static int mtk_ccifreq_probe(struct plat
ret = clk_prepare_enable(drv->cci_clk);
if (ret)
- goto out_free_resources;
+ return ret;
+
+ ret = devm_add_action_or_reset(dev, mtk_ccifreq_clk_disable_unprepare,
+ drv->cci_clk);
+ if (ret)
+ return ret;
ret = dev_pm_opp_of_add_table(dev);
- if (ret) {
- dev_err(dev, "failed to add opp table: %d\n", ret);
- goto out_disable_cci_clk;
- }
+ if (ret)
+ return dev_err_probe(dev, ret, "failed to add opp table\n");
+
+ ret = devm_add_action_or_reset(dev, mtk_ccifreq_opp_of_remove_table,
+ dev);
+ if (ret)
+ return ret;
rate = clk_get_rate(drv->inter_clk);
opp = dev_pm_opp_find_freq_ceil(dev, &rate);
- if (IS_ERR(opp)) {
- ret = PTR_ERR(opp);
- dev_err(dev, "failed to get intermediate opp: %d\n", ret);
- goto out_remove_opp_table;
- }
+ if (IS_ERR(opp))
+ return dev_err_probe(dev, PTR_ERR(opp),
+ "failed to get intermediate opp\n");
+
drv->inter_voltage = dev_pm_opp_get_voltage(opp);
dev_pm_opp_put(opp);
rate = U32_MAX;
opp = dev_pm_opp_find_freq_floor(drv->dev, &rate);
- if (IS_ERR(opp)) {
- dev_err(dev, "failed to get opp\n");
- ret = PTR_ERR(opp);
- goto out_remove_opp_table;
- }
+ if (IS_ERR(opp))
+ return dev_err_probe(dev, PTR_ERR(opp),
+ "failed to get opp\n");
opp_volt = dev_pm_opp_get_voltage(opp);
dev_pm_opp_put(opp);
@@ -349,63 +372,36 @@ static int mtk_ccifreq_probe(struct plat
if (ret) {
dev_err(dev, "failed to scale to highest voltage %lu in proc_reg\n",
opp_volt);
- goto out_remove_opp_table;
+ return ret;
}
passive_data = devm_kzalloc(dev, sizeof(*passive_data), GFP_KERNEL);
- if (!passive_data) {
- ret = -ENOMEM;
- goto out_remove_opp_table;
- }
+ if (!passive_data)
+ return -ENOMEM;
passive_data->parent_type = CPUFREQ_PARENT_DEV;
drv->devfreq = devm_devfreq_add_device(dev, &mtk_ccifreq_profile,
DEVFREQ_GOV_PASSIVE,
passive_data);
- if (IS_ERR(drv->devfreq)) {
- ret = -EPROBE_DEFER;
- dev_err(dev, "failed to add devfreq device: %ld\n",
- PTR_ERR(drv->devfreq));
- goto out_remove_opp_table;
- }
+ if (IS_ERR(drv->devfreq))
+ return dev_err_probe(dev, -EPROBE_DEFER,
+ "failed to add devfreq device: %ld\n",
+ PTR_ERR(drv->devfreq));
drv->opp_nb.notifier_call = mtk_ccifreq_opp_notifier;
ret = dev_pm_opp_register_notifier(dev, &drv->opp_nb);
- if (ret) {
- dev_err(dev, "failed to register opp notifier: %d\n", ret);
- goto out_remove_opp_table;
- }
- return 0;
-
-out_remove_opp_table:
- dev_pm_opp_of_remove_table(dev);
-
-out_disable_cci_clk:
- clk_disable_unprepare(drv->cci_clk);
-
-out_free_resources:
- if (regulator_is_enabled(drv->proc_reg))
- regulator_disable(drv->proc_reg);
- if (!IS_ERR_OR_NULL(drv->sram_reg) &&
- regulator_is_enabled(drv->sram_reg))
- regulator_disable(drv->sram_reg);
+ if (ret)
+ return dev_err_probe(dev, ret,
+ "failed to register opp notifier\n");
- return ret;
+ return 0;
}
static void mtk_ccifreq_remove(struct platform_device *pdev)
{
- struct device *dev = &pdev->dev;
- struct mtk_ccifreq_drv *drv;
-
- drv = platform_get_drvdata(pdev);
+ struct mtk_ccifreq_drv *drv = platform_get_drvdata(pdev);
- dev_pm_opp_unregister_notifier(dev, &drv->opp_nb);
- dev_pm_opp_of_remove_table(dev);
- clk_disable_unprepare(drv->cci_clk);
- regulator_disable(drv->proc_reg);
- if (drv->sram_reg)
- regulator_disable(drv->sram_reg);
+ dev_pm_opp_unregister_notifier(&pdev->dev, &drv->opp_nb);
}
static const struct mtk_ccifreq_platform_data mt8183_platform_data = {

53
target/linux/mediatek/patches-6.12/211-PM-devfreq-mtk-cci-check-cpufreq-availability-early.patch Normal file
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@ -0,0 +1,53 @@
From b19968e432fe2ebe3af4bc9190923edb70b6aeee Mon Sep 17 00:00:00 2001
From: Daniel Golle <daniel@makrotopia.org>
Date: Mon, 13 Apr 2026 15:22:05 +0100
Subject: [PATCH 2/2] PM / devfreq: mtk-cci: check cpufreq availability early
Check spufreq availablility early at probe so -EPROBE_DEFER is emitted
before touching any regulators.
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
drivers/devfreq/mtk-cci-devfreq.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
--- a/drivers/devfreq/mtk-cci-devfreq.c
+++ b/drivers/devfreq/mtk-cci-devfreq.c
@@ -4,6 +4,7 @@
*/
#include <linux/clk.h>
+#include <linux/cpufreq.h>
#include <linux/devfreq.h>
#include <linux/minmax.h>
#include <linux/module.h>
@@ -263,13 +264,28 @@ static void mtk_ccifreq_opp_of_remove_ta
static int mtk_ccifreq_probe(struct platform_device *pdev)
{
+ struct devfreq_passive_data *passive_data;
struct device *dev = &pdev->dev;
+ struct cpufreq_policy *policy;
struct mtk_ccifreq_drv *drv;
- struct devfreq_passive_data *passive_data;
struct dev_pm_opp *opp;
unsigned long rate, opp_volt;
int ret;
+ /*
+ * Check if cpufreq is available before touching any regulators.
+ * The passive devfreq governor needs cpufreq as its parent and
+ * will return -EPROBE_DEFER if it is not yet registered. If we
+ * enable the proc regulator (CPU core power) before this check,
+ * the subsequent probe failure causes devres to disable that
+ * regulator, potentially cutting CPU core voltage and hanging
+ * the system.
+ */
+ policy = cpufreq_cpu_get(0);
+ if (!policy)
+ return -EPROBE_DEFER;
+ cpufreq_cpu_put(policy);
+
drv = devm_kzalloc(dev, sizeof(*drv), GFP_KERNEL);
if (!drv)
return -ENOMEM;