The imx8m ddrc has a performance monitoring block attached which can
be used to measure bandwidth usage and automatically adjust frequency.
There is already a perf driver for that block so instead of implementing
a devfreq events driver use the in-kernel perf API to implement
get_dev_status directly.
Signed-off-by: Leonard Crestez <leonard.crestez@xxxxxxx>
---
drivers/devfreq/imx-ddrc.c | 146 ++++++++++++++++++++++++++++++++++++-
1 file changed, 143 insertions(+), 3 deletions(-)
diff --git a/drivers/devfreq/imx-ddrc.c b/drivers/devfreq/imx-ddrc.c
index 253138f608e7..f9a11a1825ea 100644
--- a/drivers/devfreq/imx-ddrc.c
+++ b/drivers/devfreq/imx-ddrc.c
@@ -11,10 +11,13 @@
#include <linux/pm_opp.h>
#include <linux/clk.h>
#include <linux/clk-provider.h>
#include <linux/arm-smccc.h>
+#include <asm/perf_event.h>
+#include <linux/perf_event.h>
+
#define IMX_SIP_DDR_DVFS 0xc2000004
/* Values starting from 0 switch to specific frequency */
#define IMX_SIP_DDR_FREQ_SET_HIGH 0x00
@@ -80,10 +83,22 @@ struct imx_ddrc {
struct clk *dram_alt;
struct clk *dram_apb;
int freq_count;
struct imx_ddrc_freq freq_table[IMX_DDRC_MAX_FREQ_COUNT];
+
+ /* For measuring load with perf events: */
+ struct platform_device *pmu_pdev;
+ struct pmu *pmu;
+
+ struct perf_event_attr rd_event_attr;
+ struct perf_event_attr wr_event_attr;
+ struct perf_event *rd_event;
+ struct perf_event *wr_event;
+
+ u64 last_rd_val, last_rd_ena, last_rd_run;
+ u64 last_wr_val, last_wr_ena, last_wr_run;
};
static struct imx_ddrc_freq *imx_ddrc_find_freq(struct imx_ddrc *priv,
unsigned long rate)
{
@@ -228,19 +243,127 @@ static int imx_ddrc_get_cur_freq(struct device *dev, unsigned long *freq)
return 0;
}
static int imx_ddrc_get_dev_status(struct device *dev,
- struct devfreq_dev_status *stat)
+ struct devfreq_dev_status *stat)
{
struct imx_ddrc *priv = dev_get_drvdata(dev);
- stat->busy_time = 0;
- stat->total_time = 0;
stat->current_frequency = clk_get_rate(priv->dram_core);
+ if (priv->rd_event && priv->wr_event) {
+ u64 rd_delta, rd_val, rd_ena, rd_run;
+ u64 wr_delta, wr_val, wr_ena, wr_run;
+
+ rd_val = perf_event_read_value(priv->rd_event,
+ &rd_ena, &rd_run);
+ wr_val = perf_event_read_value(priv->wr_event,
+ &wr_ena, &wr_run);
+
+ rd_delta = (rd_val - priv->last_rd_val) *
+ (rd_ena - priv->last_rd_ena) /
+ (rd_run - priv->last_rd_run);
+ priv->last_rd_val = rd_val;
+ priv->last_rd_ena = rd_ena;
+ priv->last_rd_run = rd_run;
+ wr_delta = (wr_val - priv->last_wr_val) *
+ (wr_ena - priv->last_wr_ena) /
+ (wr_run - priv->last_wr_run);
+ priv->last_wr_val = wr_val;
+ priv->last_wr_ena = wr_ena;
+ priv->last_wr_run = wr_run;
+
+ /* magic numbers, possibly wrong */
+ stat->busy_time = 4 * (rd_delta + wr_delta);
+ stat->total_time = stat->current_frequency;
+ } else {
+ stat->busy_time = 0;
+ stat->total_time = 0;
+ }
+
+ return 0;
+}
+
+static int imx_ddrc_perf_disable(struct imx_ddrc *priv)
+{
+ /* release and set to NULL */
+ if (!IS_ERR_OR_NULL(priv->rd_event))
+ perf_event_release_kernel(priv->rd_event);
+ if (!IS_ERR_OR_NULL(priv->wr_event))
+ perf_event_release_kernel(priv->wr_event);
+ priv->rd_event = NULL;
+ priv->wr_event = NULL;
+
+ return 0;
+}
+
+static int imx_ddrc_perf_enable(struct imx_ddrc *priv)
+{
+ int ret;
+
+ priv->rd_event_attr.size = sizeof(priv->rd_event_attr);
+ priv->rd_event_attr.type = priv->pmu->type;
+ priv->rd_event_attr.config = 0x2a;
+
+ priv->rd_event = perf_event_create_kernel_counter(
+ &priv->rd_event_attr, 0, NULL, NULL, NULL);
+ if (IS_ERR(priv->rd_event)) {
+ ret = PTR_ERR(priv->rd_event);
+ goto err;
+ }
+
+ priv->wr_event_attr.size = sizeof(priv->wr_event_attr);
+ priv->wr_event_attr.type = priv->pmu->type;
+ priv->wr_event_attr.config = 0x2b;
+
+ priv->wr_event = perf_event_create_kernel_counter(
+ &priv->wr_event_attr, 0, NULL, NULL, NULL);
+ if (IS_ERR(priv->wr_event)) {
+ ret = PTR_ERR(priv->wr_event);
+ goto err;
+ }
+
return 0;
+
+err:
+ imx_ddrc_perf_disable(priv);
+ return ret;
+}
+
+static int imx_ddrc_init_events(struct device *dev,
+ struct device_node *events_node)
+{
+ struct imx_ddrc *priv = dev_get_drvdata(dev);
+ struct device_driver *driver;
+
+ /*
+ * We need pmu->type for perf_event_attr but there is no API for
+ * mapping device_node to pmu. Fetch private data for imx-ddr-pmu and
+ * cast that to a struct pmu instead.
+ */
+ priv->pmu_pdev = of_find_device_by_node(events_node);
+ if (!priv->pmu_pdev)
+ return -EPROBE_DEFER;
+ driver = priv->pmu_pdev->dev.driver;
+ if (!driver)
+ return -EPROBE_DEFER;
+ if (strcmp(driver->name, "imx-ddr-pmu")) {
+ dev_warn(dev, "devfreq-events node %pOF has unexpected driver %s\n",
+ events_node, driver->name);
+ return -ENODEV;
+ }
+
+ priv->pmu = platform_get_drvdata(priv->pmu_pdev);
+ if (!priv->pmu) {
+ dev_err(dev, "devfreq-events device missing private data\n");
+ return -EINVAL;
+ }
+
+ dev_dbg(dev, "events from pmu %s\n", priv->pmu->name);
+
+ return imx_ddrc_perf_enable(priv);
}
static int imx_ddrc_init_freq_info(struct device *dev)
{
struct imx_ddrc *priv = dev_get_drvdata(dev);
@@ -288,10 +411,15 @@ static int imx_ddrc_init_freq_info(struct device *dev)
return 0;
}
static void imx_ddrc_exit(struct device *dev)
{
+ struct imx_ddrc *priv = dev_get_drvdata(dev);
+
+ imx_ddrc_perf_disable(priv);
+ platform_device_put(priv->pmu_pdev);
+
dev_pm_opp_of_remove_table(dev);
}
static int imx_ddrc_probe(struct platform_device *pdev)
{
@@ -337,10 +465,20 @@ static int imx_ddrc_probe(struct platform_device *pdev)
priv->profile.get_dev_status = imx_ddrc_get_dev_status;
priv->profile.exit = imx_ddrc_exit;
priv->profile.get_cur_freq = imx_ddrc_get_cur_freq;
priv->profile.initial_freq = clk_get_rate(priv->dram_core);
+ /* Handle devfreq-events */
+ events_node = of_parse_phandle(dev->of_node, "devfreq-events", 0);
+ if (events_node) {
+ ret = imx_ddrc_init_events(dev, events_node);
+ of_node_put(events_node);
+ if (ret)
+ goto err;
+ gov = DEVFREQ_GOV_SIMPLE_ONDEMAND;
+ }
+
priv->devfreq = devm_devfreq_add_device(dev, &priv->profile,
gov, NULL);
if (IS_ERR(priv->devfreq)) {
ret = PTR_ERR(priv->devfreq);
dev_err(dev, "failed to add devfreq device: %d\n", ret);
@@ -348,10 +486,12 @@ static int imx_ddrc_probe(struct platform_device *pdev)
}
return 0;
err:
+ imx_ddrc_perf_disable(priv);
+ platform_device_put(priv->pmu_pdev);
dev_pm_opp_of_remove_table(dev);
return ret;
}
static const struct of_device_id imx_ddrc_of_match[] = {
--
2.17.1
