Re: [PATCH V4 4/5] soc: qcom: Introduce SCMI based Memlat (Memory Latency) governor

[Sibi Sankar <quic_sibis@quicinc.com>]

On 10/10/24 17:48, Jonathan Cameron wrote:
> On Mon, 7 Oct 2024 11:40:22 +0530
> Sibi Sankar <quic_sibis@quicinc.com> wrote:
> 
>> Introduce a client driver that uses the memlat algorithm string
>> hosted on QCOM SCMI Generic Extension Protocol to detect memory
>> latency workloads and control frequency/level of the various
>> memory buses (DDR/LLCC/DDR_QOS).
>>
>> Co-developed-by: Shivnandan Kumar <quic_kshivnan@quicinc.com>
>> Signed-off-by: Shivnandan Kumar <quic_kshivnan@quicinc.com>
>> Co-developed-by: Ramakrishna Gottimukkula <quic_rgottimu@quicinc.com>
>> Signed-off-by: Ramakrishna Gottimukkula <quic_rgottimu@quicinc.com>
>> Co-developed-by: Amir Vajid <avajid@quicinc.com>
>> Signed-off-by: Amir Vajid <avajid@quicinc.com>
>> Signed-off-by: Sibi Sankar <quic_sibis@quicinc.com>
> I was curious. A few comments from a quick read through.
> 
> Jonathan

Hey Jonathan,

Thanks for taking time to review the series!

Will get them all addressed in the next re-spin.

-Sibi

> 
>> diff --git a/drivers/soc/qcom/qcom_scmi_memlat_client.c b/drivers/soc/qcom/qcom_scmi_memlat_client.c
>> new file mode 100644
>> index 000000000000..05198bf1f7ec
>> --- /dev/null
>> +++ b/drivers/soc/qcom/qcom_scmi_memlat_client.c
> 
>> +static int populate_cluster_info(u32 *cluster_info)
>> +{
>> +	char name[MAX_NAME_LEN];
>> +	int i = 0;
>> +
>> +	struct device_node *cn __free(device_node) = of_find_node_by_path("/cpus");
>> +	if (!cn)
>> +		return -ENODEV;
>> +
>> +	struct device_node *map __free(device_node) = of_get_child_by_name(cn, "cpu-map");
>> +	if (!map)
>> +		return -ENODEV;
>> +
>> +	do {
> while(1) {
> } >> +		snprintf(name, sizeof(name), "cluster%d", i);
>> +		struct device_node *c __free(device_node) = of_get_child_by_name(map, name);
>> +		if (!c)
>> +			break;
>> +
>> +		*(cluster_info + i) = of_get_child_count(c);
>> +		i++;
>> +	} while (1);
>> +
>> +	return 0;
>> +}
>> +
> tic struct cpufreq_memfreq_map *init_cpufreq_memfreq_map(struct device *dev,
>> +							    struct scmi_memory_info *memory,
>> +							    struct device_node *of_node,
>> +							    u32 *cnt)
>> +{
>> +	struct device_node *tbl_np __free(device_node), *opp_np __free(device_node);
>> +	struct cpufreq_memfreq_map *tbl;
>> +	int ret, i = 0;
>> +	u32 level, len;
>> +	u64 rate;
>> +
>> +	tbl_np = of_parse_phandle(of_node, "operating-points-v2", 0);
>> +	if (!tbl_np)
> 
> This will call the free on the uninitialzed opp_np above.
> Note this sort of path is why the constructor and destructor should always
> be together in the code.
> 
>> +		return ERR_PTR(-ENODEV);
>> +
>> +	len = min(of_get_available_child_count(tbl_np), MAX_MAP_ENTRIES);
>> +	if (len == 0)
>> +		return ERR_PTR(-ENODEV);
>> +
>> +	tbl = devm_kzalloc(dev, (len + 1) * sizeof(struct cpufreq_memfreq_map),
>> +			   GFP_KERNEL);
>> +	if (!tbl)
>> +		return ERR_PTR(-ENOMEM);
>> +
>> +	for_each_available_child_of_node(tbl_np, opp_np) {
> 
> Why not scoped variant which will also solve the lifetime issue above.
> 
>> +		ret = of_property_read_u64_index(opp_np, "opp-hz", 0, &rate);
>> +		if (ret < 0)
>> +			return ERR_PTR(ret);
>> +
>> +		tbl[i].cpufreq_mhz = rate / HZ_PER_MHZ;
>> +
>> +		if (memory->hw_type != QCOM_MEM_TYPE_DDR_QOS) {
>> +			ret = of_property_read_u64_index(opp_np, "opp-hz", 1, &rate);
>> +			if (ret < 0)
>> +				return ERR_PTR(ret);
>> +
>> +			tbl[i].memfreq_khz = rate / HZ_PER_KHZ;
>> +		} else {
>> +			ret = of_property_read_u32(opp_np, "opp-level", &level);
>> +			if (ret < 0)
>> +				return ERR_PTR(ret);
>> +
>> +			tbl[i].memfreq_khz = level;
>> +		}
>> +
>> +		dev_dbg(dev, "Entry%d CPU:%u, Mem:%u\n", i, tbl[i].cpufreq_mhz, tbl[i].memfreq_khz);
>> +		i++;
>> +	}
>> +	*cnt = len;
>> +
>> +	return tbl;
>> +}
>> +
>> +static int process_scmi_memlat_of_node(struct scmi_device *sdev, struct scmi_memlat_info *info)
>> +{
>> +	struct scmi_monitor_info *monitor;
>> +	struct scmi_memory_info *memory;
>> +	char name[MAX_NAME_LEN];
>> +	u64 memfreq[2];
>> +	int ret;
>> +
>> +	ret = populate_cluster_info(info->cluster_info);
>> +	if (ret < 0) {
>> +		dev_err_probe(&sdev->dev, ret, "failed to populate cluster info\n");
>> +		goto err;
> putting a node you never got?
> 		return dev_err_probe()
> 
> 
>> +	}
>> +
>> +	of_node_get(sdev->dev.of_node);
> Maybe use __free(device_node) here so you can do early returns on error.
> Will need a local variable for the return of of_node_get, but that would
> be nice anyway to simplify some parameters belwo.
> 
>> +	do {
> Might as well do while(1) {
> }
>> +		snprintf(name, sizeof(name), "memory-%d", info->memory_cnt);
>> +		struct device_node *memory_np __free(device_node) =
>> +			of_find_node_by_name(sdev->dev.of_node, name);
>> +
>> +		if (!memory_np)
>> +			break;
>> +
>> +		if (info->memory_cnt >= MAX_MEMORY_TYPES)
>> +			return dev_err_probe(&sdev->dev, -EINVAL,
>> +					     "failed to parse unsupported memory type\n");
>> +
>> +		memory = devm_kzalloc(&sdev->dev, sizeof(*memory), GFP_KERNEL);
>> +		if (!memory) {
>> +			ret = -ENOMEM;
>> +			goto err;
>> +		}
>> +
>> +		ret = of_property_read_u32(memory_np, "qcom,memory-type", &memory->hw_type);
>> +		if (ret) {
>> +			dev_err_probe(&sdev->dev, ret, "failed to read memory type\n");
>> +			goto err;
>> +		}
>> +
>> +		ret = of_property_read_u64_array(memory_np, "freq-table-hz", memfreq, 2);
>> +		if (ret && (ret != -EINVAL)) {
>> +			dev_err_probe(&sdev->dev, ret, "failed to read min/max freq\n");
>> +			goto err;
>> +		}
>> +
>> +		if (memory->hw_type != QCOM_MEM_TYPE_DDR_QOS) {
>> +			memory->min_freq = memfreq[0] / HZ_PER_KHZ;
>> +			memory->max_freq = memfreq[1] / HZ_PER_KHZ;
>> +		} else {
>> +			memory->min_freq = memfreq[0];
>> +			memory->max_freq = memfreq[1];
>> +		}
>> +		info->memory[info->memory_cnt++] = memory;
>> +
>> +		do {
>> +			snprintf(name, sizeof(name), "monitor-%d", memory->monitor_cnt);
>> +			struct device_node *monitor_np __free(device_node) =
>> +				of_get_child_by_name(memory_np, name);
>> +
>> +			if (!monitor_np)
>> +				break;
>> +
>> +			if (memory->monitor_cnt >= MAX_MONITOR_CNT)
>> +				return dev_err_probe(&sdev->dev, -EINVAL,
>> +						     "failed to parse unsupported monitor\n");
>> +
>> +			monitor = devm_kzalloc(&sdev->dev, sizeof(*monitor), GFP_KERNEL);
>> +			if (!monitor) {
>> +				ret = -ENOMEM;
>> +				goto err;
>> +			}
>> +
>> +			monitor->mon_type = of_property_read_bool(monitor_np, "qcom,compute-type");
>> +			if (!monitor->mon_type) {
>> +				ret = of_property_read_u32(monitor_np, "qcom,ipm-ceil",
>> +							   &monitor->ipm_ceil);
>> +				if (ret) {
>> +					dev_err_probe(&sdev->dev, ret,
>> +						      "failed to read IPM ceiling\n");
>> +					goto err;
>> +				}
>> +			}
>> +
>> +			/*
>> +			 * Variants of the SoC having reduced number of cpus operate
>> +			 * with the same number of logical cpus but the physical
>> +			 * cpu disabled will differ between parts. Calculate the
>> +			 * physical cpu number using cluster information instead.
>> +			 */
>> +			populate_physical_mask(monitor_np, &monitor->mask, info->cluster_info);
>> +
>> +			monitor->freq_map = init_cpufreq_memfreq_map(&sdev->dev, memory, monitor_np,
>> +								     &monitor->freq_map_len);
>> +			if (IS_ERR(monitor->freq_map)) {
>> +				dev_err_probe(&sdev->dev, PTR_ERR(monitor->freq_map),
>> +					      "failed to populate cpufreq-memfreq map\n");
>> +				goto err;
>> +			}
>> +
>> +			strscpy(monitor->mon_name, name, sizeof(monitor->mon_name));
>> +			monitor->mon_idx = memory->monitor_cnt;
>> +
>> +			memory->monitor[memory->monitor_cnt++] = monitor;
>> +		} while (1);
>> +
>> +		if (!memory->monitor_cnt) {
>> +			ret = -EINVAL;
>> +			dev_err_probe(&sdev->dev, ret, "failed to find monitor nodes\n");
>> +			goto err;
>> +		}
>> +	} while (1);
>> +
>> +	if (!info->memory_cnt) {
>> +		ret = -EINVAL;
>> +		dev_err_probe(&sdev->dev, ret, "failed to find memory nodes\n");
>> +	}
>> +
>> +err:
>> +	of_node_put(sdev->dev.of_node);
>> +
>> +	return ret;
>> +}
> 
> 
>> +
>> +static int cpucp_memlat_init(struct scmi_device *sdev)
>> +{
>> +	const struct scmi_handle *handle = sdev->handle;
>> +	const struct qcom_generic_ext_ops *ops;
>> +	struct scmi_protocol_handle *ph;
>> +	struct scmi_memlat_info *info;
>> +	u32 cpucp_freq_method = CPUCP_DEFAULT_FREQ_METHOD;
>> +	u32 cpucp_sample_ms = CPUCP_DEFAULT_SAMPLING_PERIOD_MS;
>> +	int ret, i, j;
>> +
>> +	if (!handle)
>> +		return -ENODEV;
>> +
>> +	ops = handle->devm_protocol_get(sdev, SCMI_PROTOCOL_QCOM_GENERIC, &ph);
>> +	if (IS_ERR(ops))
>> +		return PTR_ERR(ops);
>> +
>> +	info = devm_kzalloc(&sdev->dev, sizeof(*info), GFP_KERNEL);
> 
> I'd add a local variable
> 
> 	struct device *dev = &sdev->dev;
> given how many uses of this you have in this function.
> 
>> +	if (!info)
>> +		return -ENOMEM;
>> +
>> +	ret = process_scmi_memlat_of_node(sdev, info);
>> +	if (ret)
>> +		return ret;
>> +
>> +	info->ph = ph;
>> +	info->ops = ops;
>> +
>> +	/* Configure common events ids */
> As below.
>> +	ret = configure_cpucp_common_events(info);
>> +	if (ret < 0)
>> +		return dev_err_probe(&sdev->dev, ret, "failed to configure common events\n");
>> +
>> +	for (i = 0; i < info->memory_cnt; i++) {
>> +		/* Configure per group parameters */
> As below.
>> +		ret = configure_cpucp_grp(&sdev->dev, info, i);
>> +		if (ret < 0)
>> +			return ret;
>> +
>> +		for (j = 0; j < info->memory[i]->monitor_cnt; j++) {
>> +			/* Configure per monitor parameters */
> 
> I'd argue this and the above comment are clear from the function names
> so add no benefit, but not that important if you want to keep them anyway.
> Reasoning is that if a comment isn't providing more information it
> is an opportunity for bit rot in the longer run and bloats the code.
> Keep them for where they add more value.
> 
>> +			ret = configure_cpucp_mon(&sdev->dev, info, i, j);
>> +			if (ret < 0)
>> +				return ret;
>> +		}
>> +	}
> ...
> 
>> +}
>> +
>> +static int scmi_client_probe(struct scmi_device *sdev)
>> +{
>> +	return cpucp_memlat_init(sdev);
> What is benefit of this wrapper? I'd just use cpucp_memlat_init as the probe
> function.
> 
>> +}
>> +
>> +static const struct scmi_device_id scmi_id_table[] = {
> 
> Probably name this in a fashion related to the driver given
> maybe we'll have a namespace clash in future with such
> a generic name.
> 
>> +	{ SCMI_PROTOCOL_QCOM_GENERIC, "qcom-generic-ext" },
>> +	{ },
> No point in comma after a 'NULL' terminator like this.
> 
>> +};
>> +MODULE_DEVICE_TABLE(scmi, scmi_id_table);
>> +
>> +static struct scmi_driver qcom_scmi_client_drv = {
>> +	.name		= "scmi-qcom-generic-ext-memlat",
>> +	.probe		= scmi_client_probe,
>> +	.id_table	= scmi_id_table,
>> +};
>> +module_scmi_driver(qcom_scmi_client_drv);
>> +
>> +MODULE_DESCRIPTION("QTI SCMI client driver");
>> +MODULE_LICENSE("GPL");
>