[PATCH RFC] soc: qcom: icc-bwmon: Set default thresholds dynamically

[Konrad Dybcio]

Currently we use predefined threshold values. This works, but does not
really scale well, as they may differ between SoCs due to LPDDR generation
and/or DDR controller setup. All of the data we need for that is already
provided in the device tree, anyway.

Change that to:
* 0 for low (as we've been doing up until now)
* BW_MIN/4 for mid
* BW_MIN for high

The mid value is chosen for a "low enough" bw to nudge bwmon into
slowing down if the bw starts too high from the bootloader.

The high value corresponds to the upper barrier which - when crossed -
raises an interrupt in the third zone, signaling a need for upping
the bw.

This only changes the values programmed at probe time, as high and med
thresholds are updated at interrupt, based on the OPP table from DT.

Signed-off-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxx>
---
 drivers/soc/qcom/icc-bwmon.c | 28 +++++++---------------------
 1 file changed, 7 insertions(+), 21 deletions(-)

diff --git a/drivers/soc/qcom/icc-bwmon.c b/drivers/soc/qcom/icc-bwmon.c
index 40068a285913..99cbdb3cf531 100644
--- a/drivers/soc/qcom/icc-bwmon.c
+++ b/drivers/soc/qcom/icc-bwmon.c
@@ -165,9 +165,6 @@ enum bwmon_fields {
 struct icc_bwmon_data {
 	unsigned int sample_ms;
 	unsigned int count_unit_kb; /* kbytes */
-	unsigned int default_highbw_kbps;
-	unsigned int default_medbw_kbps;
-	unsigned int default_lowbw_kbps;
 	u8 zone1_thres_count;
 	u8 zone3_thres_count;
 	unsigned int quirks;
@@ -564,20 +561,21 @@ static void bwmon_set_threshold(struct icc_bwmon *bwmon,
 static void bwmon_start(struct icc_bwmon *bwmon)
 {
 	const struct icc_bwmon_data *data = bwmon->data;
+	u32 bw_low = 0;
 	int window;
 
+	/* No need to check for errors, as this must have succeeded before. */
+	dev_pm_opp_find_bw_ceil(bwmon->dev, &bw_low, 0);
+
 	bwmon_clear_counters(bwmon, true);
 
 	window = mult_frac(bwmon->data->sample_ms, HW_TIMER_HZ, MSEC_PER_SEC);
 	/* Maximum sampling window: 0xffffff for v4 and 0xfffff for v5 */
 	regmap_field_write(bwmon->regs[F_SAMPLE_WINDOW], window);
 
-	bwmon_set_threshold(bwmon, bwmon->regs[F_THRESHOLD_HIGH],
-			    data->default_highbw_kbps);
-	bwmon_set_threshold(bwmon, bwmon->regs[F_THRESHOLD_MED],
-			    data->default_medbw_kbps);
-	bwmon_set_threshold(bwmon, bwmon->regs[F_THRESHOLD_LOW],
-			    data->default_lowbw_kbps);
+	bwmon_set_threshold(bwmon, bwmon->regs[F_THRESHOLD_HIGH], bw_low);
+	bwmon_set_threshold(bwmon, bwmon->regs[F_THRESHOLD_MED], div_u64(bw_low, 4));
+	bwmon_set_threshold(bwmon, bwmon->regs[F_THRESHOLD_LOW], 0);
 
 	regmap_field_write(bwmon->regs[F_THRESHOLD_COUNT_ZONE0],
 			   BWMON_THRESHOLD_COUNT_ZONE0_DEFAULT);
@@ -807,9 +805,6 @@ static int bwmon_remove(struct platform_device *pdev)
 static const struct icc_bwmon_data msm8998_bwmon_data = {
 	.sample_ms = 4,
 	.count_unit_kb = 1024,
-	.default_highbw_kbps = 4800 * 1024, /* 4.8 GBps */
-	.default_medbw_kbps = 512 * 1024, /* 512 MBps */
-	.default_lowbw_kbps = 0,
 	.zone1_thres_count = 16,
 	.zone3_thres_count = 1,
 	.quirks = BWMON_HAS_GLOBAL_IRQ,
@@ -822,9 +817,6 @@ static const struct icc_bwmon_data msm8998_bwmon_data = {
 static const struct icc_bwmon_data sdm845_cpu_bwmon_data = {
 	.sample_ms = 4,
 	.count_unit_kb = 64,
-	.default_highbw_kbps = 4800 * 1024, /* 4.8 GBps */
-	.default_medbw_kbps = 512 * 1024, /* 512 MBps */
-	.default_lowbw_kbps = 0,
 	.zone1_thres_count = 16,
 	.zone3_thres_count = 1,
 	.quirks = BWMON_HAS_GLOBAL_IRQ,
@@ -835,9 +827,6 @@ static const struct icc_bwmon_data sdm845_cpu_bwmon_data = {
 static const struct icc_bwmon_data sdm845_llcc_bwmon_data = {
 	.sample_ms = 4,
 	.count_unit_kb = 1024,
-	.default_highbw_kbps = 800 * 1024, /* 800 MBps */
-	.default_medbw_kbps = 256 * 1024, /* 256 MBps */
-	.default_lowbw_kbps = 0,
 	.zone1_thres_count = 16,
 	.zone3_thres_count = 1,
 	.regmap_fields = sdm845_llcc_bwmon_reg_fields,
@@ -847,9 +836,6 @@ static const struct icc_bwmon_data sdm845_llcc_bwmon_data = {
 static const struct icc_bwmon_data sc7280_llcc_bwmon_data = {
 	.sample_ms = 4,
 	.count_unit_kb = 64,
-	.default_highbw_kbps = 800 * 1024, /* 800 MBps */
-	.default_medbw_kbps = 256 * 1024, /* 256 MBps */
-	.default_lowbw_kbps = 0,
 	.zone1_thres_count = 16,
 	.zone3_thres_count = 1,
 	.quirks = BWMON_NEEDS_FORCE_CLEAR,

---
base-commit: 49dd846128d56199db2e3bcfca42d87fbc82b212
change-id: 20230610-topic-bwmon_opp-f995bbdd18bd

Best regards,
-- 
Konrad Dybcio <konrad.dybcio@xxxxxxxxxx>