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

[Konrad Dybcio]

On 10.06.2023 14:02, Konrad Dybcio wrote:
> 
> 
> On 10.06.2023 14:01, Konrad Dybcio wrote:
>> 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>
>> ---
> I think I hit a b4 bug and it didn't send this notice..:
> 
> Depends on: https://lore.kernel.org/linux-arm-msm/d403e841-7a86-1f07-c634-1990902826f1@xxxxxxxxxx/
> 
> Konrad
>>  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));
Giving it a spin on more platforms, div4 seems to be.. too harsh for some?

MSM8998 boots fine if I divide it by 2, but crashes when I divide by 4..

Note sure what to make out of it..

Konrad
>> +	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,